| 1. |
- Rubio-Magnieto, Jenifer, et al.
(författare)
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Binding Modes and Selectivity of Ruthenium Complexes to Human Telomeric DNA G-Quadruplexes
- 2018
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Ingår i: Chemistry - A European Journal. - : WILEY-V C H VERLAG GMBH. - 0947-6539 .- 1521-3765. ; 24:58, s. 15577-15588
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Tidskriftsartikel (refereegranskat)abstract
- Metal complexes constitute an important class of DNA binders. In particular, a few ruthenium polyazaaromatic complexes are attractive as light switches because of their strong luminescence enhancement upon DNA binding. In this paper, a comprehensive study on the binding modes of several mononuclear and binuclear ruthenium complexes to human telomeric sequences, made of repeats of the d(TTAGGG) fragment is reported. These DNA sequences form G-quadruplexes (G4s) at the ends of chromosomes and constitute a relevant biomolecular target in cancer research. By combining spectroscopy experiments and molecular modelling simulations, several key properties are deciphered: the binding modes, the stabilization of G4 upon binding, and the selectivity of these complexes towards G4 versus double-stranded DNA. These results are rationalized by assessing the possible deformation of G4 and the binding free energies of several binding modes via modelling approaches. Altogether, this comparative study provides fundamental insights into the molecular recognition properties and selectivity of Ru complexes towards this important class of DNA G4s.
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| 2. |
- Holmgaard List, Nanna, et al.
(författare)
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Origin of DNA-Induced Circular Dichroism in a Minor-Groove Binder
- 2017
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 139:42, s. 14947-14953
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Tidskriftsartikel (refereegranskat)abstract
- Induced circular dichroism (ICD) of DNA-binding ligands is well known to be strongly influenced by the specific mode of binding, but the relative importance of the possible mechanisms has remained undetermined. With a combination of molecular dynamics simulations, CD response calculations, and experiments on an AT-sequence, we show that the ICD of minor-groove-bound 4',6-diamidino-2-phenylindole (DAPI) originates from an intricate interplay between the chiral imprint of DNA, off-resonant excitonic coupling to nucleobases, charge-transfer, and resonant excitonic coupling between DAPIs. The significant contributions from charge-transfer and the chiral imprint to the ICD demonstrate the inadequacy of a standard Frenkel exciton theory of the DAPI-DNA interactions.
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| 3. |
- Støchkel, K., et al.
(författare)
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On the influence of water on the electronic structure of firefly oxyluciferin anions from absorption spectroscopy of bare and monohydrated ions in vacuo
- 2013
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 135:17, s. 6485-6493
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Tidskriftsartikel (refereegranskat)abstract
- A complete understanding of the physics underlying the varied colors of firefly bioluminescence remains elusive because it is difficult to disentangle different enzyme-lumophore interactions. Experiments on isolated ions are useful to establish a proper reference when there are no microenvironmental perturbations. Here, we use action spectroscopy to compare the absorption by the firefly oxyluciferin lumophore isolated in vacuo and complexed with a single water molecule. While the process relevant to bioluminescence within the luciferase cavity is light emission, the absorption data presented here provide a unique insight into how the electronic states of oxyluciferin are altered by microenvironmental perturbations. For the bare ion we observe broad absorption with a maximum at 548 ± 10 nm, and addition of a water molecule is found to blue-shift the absorption by approximately 50 nm (0.23 eV). Test calculations at various levels of theory uniformly predict a blue-shift in absorption caused by a single water molecule, but are only qualitatively in agreement with experiment highlighting limitations in what can be expected from methods commonly used in studies on oxyluciferin. Combined molecular dynamics simulations and time-dependent density functional theory calculations closely reproduce the broad experimental peaks and also indicate that the preferred binding site for the water molecule is the phenolate oxygen of the anion. Predicting the effects of microenvironmental interactions on the electronic structure of the oxyluciferin anion with high accuracy is a nontrivial task for theory, and our experimental results therefore serve as important benchmarks for future calculations.
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| 4. |
- Zhang, Li, et al.
(författare)
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pi-Extended perylene diimide double-heterohelicenes as ambipolar organic semiconductors for broadband circularly polarized light detection
- 2021
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Ingår i: Nature Communications. - : Nature Research. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Despite great challenges, the development of new molecular structures with multiple and even conflicting characteristics are eagerly pursued for exploring advanced applications. To develop high-performance chiral organic semiconducting molecules, a distorted -system is required for strong coupling with circularly polarized light (CPL), whereas planar pi -stacking systems are necessary for high charge-carrier mobility. To address this dilemma, in this work, we introduce a skeleton merging approach through distortion of a perylene diimide (PDI) core with four fused heteroaromatics to form an ortho-pi -extended PDI double-[7]heterohelicene. PDI double helicene inherits a high dissymmetry factor from the helicene skeleton, and the extended pi -planar system concurrently maintains a high level of charge transport properties. In addition, ortho-pi -extension of the PDI skeleton brings about near-infrared (NIR) light absorption and ambipolar charge transport abilities, endowing the corresponding organic phototransistors with high photoresponsivity of 450 and 120mAW(-1) in p- and n-type modes respectively, along with a high external quantum efficiency (89%) under NIR light irradiations. Remarkably, these multiple characteristics enable high-performance broadband CPL detections up to NIR spectral region with chiral organic semiconductors. In organic semiconducting molecules materials, distorted pi -systems enable strong coupling with circular polarized light while planar pi -stacking systems are necessary for high charge-carrier mobility. Here, the authors address this dilemma by introducing a skeleton merging approach through distortion of a perylene diimide core with four fused heteroaromatics to form a pi -extended double helicene.
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| 5. |
- Ahrén, Maria, et al.
(författare)
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A simple polyol-free synthesis route to Gd 2O 3 nanoparticles for MRI applications : An experimental and theoretical study
- 2012
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Ingår i: Journal of nanoparticle research. - : Springer. - 1388-0764 .- 1572-896X. ; 14:8
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Tidskriftsartikel (refereegranskat)abstract
- Chelated gadolinium ions, e.g., Gd-DTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd 2O 3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r 1 and r 2 values almost as high as those for free Gd 3+ ions in water. The Gd 2O 3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.
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| 6. |
- Ahrén, Maria, et al.
(författare)
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One-step synthesis of sub 5 nm sized manganese oxide based nanoparticles
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Sub 5 nm sized manganese oxide nanoparticles; MnOx (1 ≤ x ≤ 2), were synthesized via a short time room temperature synthesis route. The nanoparticles are crystalline, spherically shaped and in the size range of 2-4 nm as shown by transmission electron microscopy studies. Selected area electron diffraction patterns were collected and their appearance indicated that the nanoparticle cores are composed of MnO. Also, co-existence of the (II) and (III) oxidation states at the nanoparticle surface was verified by results achieved from infrared spectroscopy and X-ray photoelectron spectroscopy. These measurements also supported presence of a minor amount of acetate groups as well as a negligible fraction of carbonate groups at the nanoparticle surfaces. The interpretation of the IR spectra was confirmed by quantum chemical calculations using the high spin manganese nanoparticle Mn12O12(OAc)16(H2O)4, as a model system for the MnOx nanoparticle surface. Bulk MnO and Mn2O3 are known to be antiferromagnetic. The magnetic properties are however somewhat dependent of the crystallite size and changes when scaling down to the nanoregion. The MnOx (1 ≤ x ≤ 2) nanoparticles investigated in this work show a superparamagnetic behavior with a blocking temperature of approximately 12 K proven by means of SQUID measurements. The relaxivities of the nanoparticles and the Mn(OAc)2 precursors were studied with a bench top NMR analyzer verifying nanoparticle r1 and r2 of 0.5 and 6 mMs-1 respectively. The r1 relaxivity is lower than what is earlier reported for Gd based contrast agent, but improvements are expected by further surface modification, due to increased rotational time and higher water dispersability.
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| 7. |
- Andersson, Åke, et al.
(författare)
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Indication of 310-Helix Structure in Gas-Phase Neutral Pentaalanine
- 2022
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 127:4, s. 938-45
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the gas-phase structure of the neutral pentaalanine peptide. The IR spectrum in the 340-1820 cm-1 frequency range is obtained by employing supersonic jet cooling, infrared multiphoton dissociation, and vacuum-ultraviolet action spectroscopy. Comparison with quantum chemical spectral calculations suggests that the molecule assumes multiple stable conformations, mainly of two structure types. In the most stable conformation theoretically found, the N-terminus forms a C5 ring and the backbone resembles that of an 310-helix with two β-turns. Additionally, the conformational preferences of pentaalanine have been evaluated using Born-Oppenheimer molecular dynamics, showing that a nonzero simulation time step causes a systematic frequency shift.
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| 8. |
- Apostolopoulou-Kalkavoura, Varvara, 1988-, et al.
(författare)
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Humidity-Dependent Thermal Boundary Conductance Controls Heat Transport of Super-Insulating Nanofibrillar Foams
- 2021
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Ingår i: Matter. - : Elsevier BV. - 2590-2393 .- 2590-2385. ; 4:1, s. 276-289
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanomaterial (CNM)-based foams and aerogels with thermal conductivities substantially below the value for air attract significant interest as super-insulating materials in energy-efficient green buildings. However, the moisture dependence of the thermal conductivity of hygroscopic CNM-based materials is poorly understood, and the importance of phonon scattering in nanofibrillar foams remains unexplored. Here, we show that the thermal conductivity perpendicular to the aligned nanofibrils in super-insulating ice-templated nanocellulose foams is lower for thinner fibrils and depends strongly on relative humidity (RH), with the lowest thermal conductivity (14 mW m−1 K−1) attained at 35% RH. Molecular simulations show that the thermal boundary conductance is reduced by the moisture-uptake-controlled increase of the fibril-fibril separation distance and increased by the replacement of air with water in the foam walls. Controlling the heat transport of hygroscopic super-insulating nanofibrillar foams by moisture uptake and release is of potential interest in packaging and building applications.
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| 9. |
- Arja, Katriann, et al.
(författare)
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Self-Assembly of Chiro-Optical Materials from Nonchiral Oligothiophene-Porphyrin Derivatives and Random Coil Synthetic Peptides
- 2023
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Ingår i: ChemPlusChem. - : Wiley. - 2192-6506. ; 88:1
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Tidskriftsartikel (refereegranskat)abstract
- Biomimetic chiral optoelectronic materials can be utilized in electronic devices, biosensors and artificial enzymes. Herein, this work reports the chiro-optical properties and architectural arrangement of optoelectronic materials generated from self-assembly of initially nonchiral oligothiophene−porphyrin derivatives and random coil synthetic peptides. The photo-physical- and structural properties of the materials were assessed by absorption-, fluorescence- and circular dichroism spectroscopy, as well as dynamic light scattering, scanning electron microscopy and theoretical calculations. The materials display a three-dimensional ordered helical structure and optical activity that are observed due to an induced chirality of the optoelectronic element upon interaction with the peptide. Both these properties are influenced by the chemical composition of the oligothiophene−porphyrin derivative, as well as the peptide sequence. We foresee that our findings will aid in developing self-assembled optoelectronic materials with dynamic architectonical accuracies, as well as offer the possibility to generate the next generation of materials for a variety of bioelectronic applications.
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| 10. |
- Augusto Berrocal, Jose, et al.
(författare)
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Consequences of conformational flexibility in hydrogen-bond-driven self-assembly processes
- 2016
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Ingår i: Chemical Communications. - : ROYAL SOC CHEMISTRY. - 1359-7345 .- 1364-548X. ; 52:72, s. 10870-10873
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Tidskriftsartikel (refereegranskat)abstract
- We report the synthesis and self-assembly of chiral, conformationally flexible C-3-symmetrical trisamides. A strong Cotton effect is observed for the supramolecular polymers in linear alkanes but not in cyclic alkanes. MD simulations suggest 2:1 conformations of the amides within the aggregates in both types of solvents, but a chiral bias in only linear alkanes.
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| 11. |
- Bian, Qingzhen, 1988-, et al.
(författare)
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Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes
- 2020
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Charge separation dynamics after the absorption of a photon is a fundamental process relevant both for photosynthetic reaction centers and artificial solar conversion devices. It has been proposed that quantum coherence plays a role in the formation of charge carriers in organic photovoltaics, but experimental proofs have been lacking. Here we report experimental evidence of coherence in the charge separation process in organic donor/acceptor heterojunctions, in the form of low frequency oscillatory signature in the kinetics of the transient absorption and nonlinear two-dimensional photocurrent spectroscopy. The coherence plays a decisive role in the initial 200 femtoseconds as we observe distinct experimental signatures of coherent photocurrent generation. This coherent process breaks the energy barrier limitation for charge formation, thus competing with excitation energy transfer. The physics may inspire the design of new photovoltaic materials with high device performance, which explore the quantum effects in the next-generation optoelectronic applications.
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| 12. |
- Björk, Linnea, et al.
(författare)
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Distinct Heterocyclic Moieties Govern the Selectivity of Thiophene‐Vinylene‐Based Ligands towards Aβ or Tau Pathology in Alzheimer's Disease
- 2023
-
Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 26:41, s. e202300583-
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Tidskriftsartikel (refereegranskat)abstract
- Distinct aggregated proteins are correlated with numerous neurodegenerative diseases and the development of ligands that selectively detect these pathological hallmarks is vital. Recently, the synthesis of thiophene-based optical ligands, denoted bi-thiophene-vinyl-benzothiazoles (bTVBTs), that could be utilized for selective assignment of tau pathology in brain tissue with Alzheimer's disease (AD) pathology, was reported. Herein, we investigate the ability of these ligands to selectively distinguish tau deposits from aggregated amyloid-β (Aβ), the second AD associated pathological hallmark, when replacing the terminal thiophene moiety with other heterocyclic motifs. The selectivity for tau pathology was reduced when introducing specific heterocyclic motifs, verifying that specific molecular interactions between the ligands and the aggregates are necessary for selective detection of tau deposits. In addition, ligands having certain heterocyclic moieties attached to the central thiophene-vinylene building block displayed selectivity to aggregated Aβ pathology. Our findings provide chemical insights for the development of ligands that can distinguish between aggregated proteinaceous species consisting of different proteins and might also aid in creating novel agents for clinical imaging of tau pathology in AD.
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| 13. |
- Bouchet, Aude, et al.
(författare)
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Conformational Effects Induced by Guest Encapsulation in an Enantiopure Water-Soluble Cryptophane
- 2011
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:5, s. 1372-1383
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Tidskriftsartikel (refereegranskat)abstract
- A new water-soluble cryptophane 1 derivative (penta-hydroxyl cryptophane-A) has been synthesized from cryptophanol-A and the chiroptical properties of its two enantiomers M M-1 and P P-1 have been studied by polarimetry, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD). Cryptophane 1 shows specific circular dichroism responses upon complexation that depend on the size of the guest and on the nature of the counterion (Li+, Na+, K+, Cs+) present in the solution. In LiOH and NaOH solutions, chiroptical changes induced by the encapsulation of guests and by the presence of cations in the vicinity of hosts can be interpreted from molecular dynamics (MD) and ab initio calculations by subtle conformational changes of the bridges. In KOH solution, the exchange dynamics is dependent on the size of the guest molecules, whereas in CsOH solution no encapsulation effect is observed whatever the size of the guest molecule. This last behavior comes from the fact that host 1 exhibits a very high affinity for cesium cations.
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| 14. |
- Bouchet, Aude, et al.
(författare)
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Enantioselective Complexation of Chiral Propylene Oxide by an Enantiopure Water-Soluble Cryptophane
- 2011
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 76:10, s. 4178-4181
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Tidskriftsartikel (refereegranskat)abstract
- ECD and NMR experiments show that the complexation of propylene oxide (PrO) within the cavity of an enantiopure water-soluble cryptophane 1 in NaOH solution is enantioselective and that the (R)-PrO@PP-1 diastereomer is more stable than the (S)-PrO@PP-1 diastereomer with a free energy difference of 1.7 kJ/mol. This result has been confirmed to by molecular dynamics (MD) and ab initio calculations. The enantioselectivity is preserved in LiOH and KOH solutions even though the binding constants decrease, whereas PrO is not complexed in CsOH solution.
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| 15. |
- Bouchet, Aude, et al.
(författare)
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Influence of the Chemical Structure of Water-Soluble Cryptophanes on Their Overall Chiroptical and Binding Properties
- 2011
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society. - 0022-3263 .- 1520-6904. ; 76:19, s. 7816-7825
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and the chiroptical properties of the two enantiomers of the hexacarboxylic acid cryptophane-A derivative, 1, are described in this article. The chiroptical and binding properties of 1 toward achiral and chiral guests have been investigated in water under basic conditions by polarimetry, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and (1)H NMR spectroscopy. These experiments reveal that the (1)H NMR spectra of 1 are very sensitive to the nature of the guest trapped in its cavity whereas ECD and VCD spectra remain unchanged. We also show that the two enantiomers of 1 are able to distinguish between the two enantiomers of a series of small chiral epoxides. The enantiodiscrimination increases with the size of the chiral guest whereas the corresponding binding constants decrease. In contrast to what was observed for other water-soluble cryptophanes, the molecular recognition process is found independent of the nature of the counterions surrounding host 1, shedding light on the importance of the chemical structure of cryptophanes on their binding and chiroptical properties.
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| 16. |
- Brede, Jens, et al.
(författare)
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Adsorption and conformation of porphyrins on metallic surfaces
- 2009
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Ingår i: JOURNAL OF VACUUM SCIENCE and TECHNOLOGY B. - : American Vacuum Society. - 1071-1023. ; 27:2, s. 799-804
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Tidskriftsartikel (refereegranskat)abstract
- Tetraphenyl porphyrins (TPP) belong to a highly interesting class of molecules with a large variety of electronic, magnetic, and structural properties. So far, local investigations by scanning probe techniques were primarily focused on larger agglomerates of TPP molecules. Here, experimental results of the observation and manipulation of isolated molecules adsorbed on cold metal substrates by means of low temperature scanning tunneling microscopy are presented. Depending on the surface geometry, i.e., Cu(111) VS, Cu(100) three distinct deformations of the molecular structure are identified reflecting the interaction of the phenyl periphery with the substrate. In a second step, controlled manipulation in terms of deformation of the porphyrin core, ligand dissociation, and lateral displacement of the phenyl periphery are demonstrated.
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| 17. |
- Brede, Jens, et al.
(författare)
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Dynamics of molecular self-ordering in tetraphenyl porphyrin monolayers on metallic substrates
- 2009
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Ingår i: NANOTECHNOLOGY. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 20:27, s. 275602-
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Tidskriftsartikel (refereegranskat)abstract
- A molecular model system of tetraphenyl porphyrins (TPP) adsorbed on metallic substrates is systematically investigated within a joint scanning tunnelling microscopy/molecular modelling approach. The molecular conformation of TPP molecules, their adsorption on a gold surface and the growth of highly ordered TPP islands are modelled with a combination of density functional theory and dynamic force field methods. The results indicate a subtle interplay between different contributions. The molecule-substrate interaction causes a bending of the porphyrin core which also determines the relative orientations of phenyl legs attached to the core. A major consequence of this is a characteristic (and energetically most favourable) arrangement of molecules within self-assembled molecular clusters; the phenyl legs of adjacent molecules are not aligned parallel to each other (often denoted as pi-pi stacking) but perpendicularly in a T-shaped arrangement. The results of the simulations are fully consistent with the scanning tunnelling microscopy observations, in terms of the symmetries of individual molecules, orientation and relative alignment of molecules in the self-assembled clusters.
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| 18. |
- Brocorens, Patrick, et al.
(författare)
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Conformational Plasticity of Hydrogen Bonded Bis-urea Supramolecular Polymers
- 2013
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society. - 1520-6106 .- 1520-5207. ; 117:17, s. 5379-5386
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Tidskriftsartikel (refereegranskat)abstract
- We report a detailed structural investigation of supramolecular polymers formed by hydrogen bonded self assembly of bis-urea monomers The careful exploration of the energy landscape by molecular mechanics/molecular dynamics (MM/MD) simulations has allowed us to identify three distinct self assembled structures of similar stabilities. These structures have been compared to X-ray crystal data. We observe that a slight change in the molecular structure can favor a particular structure over the others. Detailed analysis shows that hydrogen bonds stabilize all three structures to a similar extent Therefore, it is the interactions among the lateral substituents, and with the filament environment, that are the decisive factors in the competition between the possible self-assembled structures. This study constitutes a clear reminder that the conformation of a supramolecular polymer is a sensitive function of the molecular structure and may significantly differ from the solid-state conformation of a model compound.
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| 19. |
- Brossier, Mathis, et al.
(författare)
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Moliverse: Contextually embedding the microcosm into the universe
- 2023
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Ingår i: Computers & graphics. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0097-8493 .- 1873-7684. ; 112, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- We present Moliverse, an integration of the molecular visualization framework VIAMD into the astronomical visualization software OpenSpace, allowing us to bridge the two extreme ends of the scale spectrum to show, for example, the gas composition in a planets atmosphere or molecular structures in comet trails and can empower the creation of educational exhibitions. For that purpose we do not use a linear scale traversal but break the scale continuity and show molecular simulations as focus in the context of celestial bodies. We demonstrate the application of our concept in two storytelling scenarios and envision the application both for science presentations to lay audiences and for dedicated exploration, potentially also in a molecule-only environment.
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| 20. |
- Brotin, Thierry, et al.
(författare)
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High Affinity of Water-Soluble Cryptophanes for Cesium Cations
- 2012
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 77:2, s. 1198-1201
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Tidskriftsartikel (refereegranskat)abstract
- Exceptionally high affinity for cesium cations was achieved in aqueous solution using two enantiopure cryptophanes. Complexation of cesium was evidenced by Cs-133 NMR spectroscopy and by electronic circular dichroism (ECD). Binding constants as high as 6 X 10(9) M-1 have been measured by isothermal titration calorimetry (ITC). Very strong complexation of rubidium cations (K similar to 10(6) M-1) has also been measured. Chiral hosts allowed the detection of the two cations at low concentrations (mu M) using ECD.
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| 21. |
- Bäck, Marcus, et al.
(författare)
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Tyrosine Side-Chain Functionalities at Distinct Positions Determine the Chirooptical Properties and Supramolecular Structures of Pentameric Oligothiophenes
- 2020
-
Ingår i: ChemistryOpen. - : Wiley. - 2191-1363. ; 9:11, s. 1100-1108
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Tidskriftsartikel (refereegranskat)abstract
- Control over the photophysical properties and molecular organization of pi-conjugated oligothiophenes is essential to their use in organic electronics. Herein we synthesized and characterized a variety of anionic pentameric oligothiophenes with different substitution patterns of L- or D-tyrosine at distinct positions along the thiophene backbone. Spectroscopic, microscopic, and theoretical studies of L- or D-tyrosine substituted pentameric oligothiophene conjugates revealed the formation of optically active pi-stacked self-assembled aggregates under acid conditions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies, were highly influenced by the positioning of the L- or D-tyrosine moieties along the thiophene backbone. Overall, the obtained results clearly demonstrate how fundamental changes in the position of the enantiomeric side-chain functionalities greatly affect the optical properties as well as the architecture of the self-assembled supramolecular structures.
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| 22. |
- Böhlin, Johan, et al.
(författare)
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Effect of dynamic disorder on charge transport along a pentacene chain
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 83:8, s. 085209-
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Tidskriftsartikel (refereegranskat)abstract
- The lattice equation of motion and a numerical solution of the time-dependent Schrodinger equation provide us with amicroscopic picture of charge transport in highly ordered molecular crystals. We have chosen the pentacene single crystal as a model system, and we study charge transport as a function of phonon-mode time-dependent fluctuations in the intermolecular electron transfer integral. For comparison, we include similar fluctuations also in the intramolecular potentials. The variance in these energy quantities is closely related to the temperature of the system. The pentacene system is shown to be very sensitive to fluctuation in the intermolecular transfer integral, revealing a transition from adiabatic to nonadiabatic polaron transport for increasing temperatures. The extension of the polaron at temperatures above 200 K is limited by the electron localization length rather than the interplay between the electron transfer integral and the electron-phonon coupling strength.
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| 23. |
- Charalambidis, Georgios, et al.
(författare)
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A switchable self-assembling and disassembling chiral system based on a porphyrin-substituted phenylalanine-phenylalanine motif
- 2016
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 7:12657
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Tidskriftsartikel (refereegranskat)abstract
- Artificial light-harvesting systems have until now not been able to self-assemble into structures with a large photon capture cross-section that upon a stimulus reversibly can switch into an inactive state. Here we describe a simple and robust FLFL-dipeptide construct to which a meso-tetraphenylporphyrin has been appended and which self-assembles to fibrils, platelets or nanospheres depending on the solvent composition. The fibrils, functioning as quenched antennas, give intense excitonic couplets in the electronic circular dichroism spectra which are mirror imaged if the unnatural FDFD-analogue is used. By slightly increasing the solvent polarity, these light-harvesting fibres disassemble to spherical structures with silent electronic circular dichroism spectra but which fluoresce. Upon further dilution with the nonpolar solvent, the intense Cotton effects are recovered, thus proving a reversible switching. A single crystal X-ray structure shows a head-to-head arrangement of porphyrins that explains both their excitonic coupling and quenched fluorescence.
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| 24. |
- Christodoulou, C., et al.
(författare)
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Tuning the work function of graphene-on-quartz with a high weight molecular acceptor
- 2014
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 118:9, s. 4784-4790
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Tidskriftsartikel (refereegranskat)abstract
- Ultraviolet and X-ray photoelectron spectroscopies in combination with density functional theory (DFT) calculations were used to study the change in the work function (Φ) of graphene, supported by quartz, as induced by adsorption of hexaazatriphenylene-hexacarbonitrile (HATCN). Near edge X-ray absorption fine structure spectroscopy (NEXAFS) and DFT modeling show that a molecular-density-dependent reorientation of HATCN from a planar to a vertically inclined adsorption geometry occurs upon increasing surface coverage. This, in conjunction with the orientation-dependent magnitude of the interface dipole, allows one to explain the evolution of graphene Φ from 4.5 eV up to 5.7 eV, rendering the molecularly modified graphene-on-quartz a highly suitable hole injection electrode.
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| 25. |
- Cooper, Thomas M., et al.
(författare)
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Nanoscale Organization of a Platinum(II) Acetylide Cholesteric Liquid Crystal Molecular Glass for Photonics Applications
- 2020
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 30:28
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Tidskriftsartikel (refereegranskat)abstract
- The fabrication, molecular structure, and spectroscopy of a stable cholesteric liquid crystal platinum acetylide glass obtained from trans-Pt(PEt3)(2)(C(sic)C-C6H5-C(sic)N)(C(sic)C-C6H5-COO-Cholesterol), are described and designated as PE1-CN-Chol. Polarized optical microscopy, differential scanning calorimetry, and wide-angle X-ray scattering experiments show room temperature glassy/crystalline texture with crystal formation upon heating to 165 degrees C. Further heating results in conversion to cholesteric phase. Cooling to room temperature leads to the formation of a cholesteric liquid crystal glass. Scanning tunneling microscopy of a PE1-CN-Chol monolayer reveals self-assembly at the solid-liquid interface with an array of two molecules arranged in pairs, oriented head-to-head through the CN groups, giving rise to a lamella arrangement. The lamella structure obtained from molecular dynamics calculations shows a clear phase separation between the conjugated platinum acetylide and the hydrophobic cholesterol moiety with the lamellae separation distance being 4.0 nm. Ultrafast transient absorption and flash photolysis spectra of the glass show intersystem crossing to the triplet state occurring within 100 ps following excitation. The triplet decay time of the film compared to aerated and deoxygenated solutions is consistent with oxygen quenching at the film surface but not within the film. The high chromophore concentration, high glass thermal stability, and long triplet lifetime in air show that these materials have potential as nonlinear absorbing materials.
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| 26. |
- Cornelissen, Tim, et al.
(författare)
-
Kinetic Monte Carlo simulations of organic ferroelectrics
- 2019
-
Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 21:3, s. 1375-1383
-
Tidskriftsartikel (refereegranskat)abstract
- Ferroelectrics find broad applications, e.g. in non-volatile memories, but the switching kinetics in real, disordered, materials is still incompletely understood. Here, we develop an electrostatic model to study ferroelectric switching using 3D Monte Carlo simulations. We apply this model to the prototypical small molecular ferroelectric trialkylbenzene-1,3,5-tricarboxamide (BTA) and find good agreement between the Monte Carlo simulations, experiments, and molecular dynamics studies. Since the model lacks any explicit steric effects, we conclude that these are of minor importance. While the material is shown to have a frustrated antiferroelectric ground state, it behaves as a normal ferroelectric under practical conditions due to the large energy barrier for switching that prevents the material from reaching its ground state after poling. We find that field-driven polarization reversal and spontaneous depolarization have orders of magnitude different switching kinetics. For the former, which determines the coercive field and is relevant for data writing, nucleation occurs at the electrodes, whereas for the latter, which governs data retention, nucleation occurs at disorder-induced defects. As a result, by reducing the disorder in the system, the polarization retention time can be increased dramatically while the coercive field remains unchanged.
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| 27. |
- Danila, Ion, et al.
(författare)
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Hierarchical Chiral Expression from the Nano- to Mesoscale in Synthetic Supramolecular Helical Fibers of a Nonamphiphilic C(3)-Symmetrical pi-Functional Molecule
- 2011
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 133:21, s. 8344-8353
-
Tidskriftsartikel (refereegranskat)abstract
- The controlled preparation of chiral structures is a contemporary challenge for supramolecular science because of the interesting properties that can arise from the resulting materials, and here we show that a synthetic nonamphiphilic C(3) compound containing pi-functional tetrathiafulvalene units can form this kind of object. We describe the synthesis, characterization, and self-assembly properties in solution and in the solid state of the enantiopure materials. Circular dichroism (CD) measurements show optical activity resulting from the presence of twisted stacks of preferential helicity and also reveal the critical importance of fiber nucleation in their formation. Molecular mechanics (MM) and molecular dynamics (MD) simulations combined with CD theoretical calculations demonstrate that the (5) enantiomer provides the (M) helix, which is more stable than the (P) helix for this enantiomer. This relationship is for the first time established in this family of C(3) symmetric compounds. In addition, we show that introduction of the "wrong" enantiomer in a stack decreases the helical reversal barrier in a nonlinear manner, which very probably accounts for the absence of a "majority rules" effect. Mesoscopic chiral fibers, which show inverted helicity, i.e. (P) for the (S) enantiomer and (M) for the (R) one, have been obtained upon reprecipitation from dioxane and analyzed by optical and electronic microscopy. The fibers obtained with the racemic mixture present, as a remarkable feature, opposite homochiral domains within the same fiber, separated by points of helical reversal. Their formation can be explained through an "oscillating" crystallization mechanism. Although C(3) symmetric disk-shaped molecules containing a central benzene core substituted in the 1,3,5 positions with 3,3'-diamido-2,2'-bipyridine based wedges have shown peculiar self-assembly properties for amphiphilic derivatives, the present result shows the benefits of reducing the nonfunctional part of the molecule, in our case with short chiral isopentyl chains. The research reported herein represents an important step toward the preparation of functional mesostructures with controlled helical architectures.
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| 28. |
- De Oliveira, Danilo Hirabae, et al.
(författare)
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Silk Assembly against Hydrophobic Surfaces?Modeling and Imaging of Formation of Nanofibrils
- 2023
-
Ingår i: ACS Applied Bio Materials. - : AMER CHEMICAL SOC. - 2576-6422. ; 6:3, s. 1011-1018
-
Tidskriftsartikel (refereegranskat)abstract
- A detailed insight about the molecular organization behind spider silk assembly is valuable for the decoding of the unique properties of silk. The recombinant partial spider silk protein 4RepCT contains four poly-alanine/glycine-rich repeats followed by an amphiphilic C-terminal domain and has shown the capacity to self-assemble into fibrils on hydrophobic surfaces. We herein use molecular dynamic simulations to address the structure of 4RepCT and its different parts on hydrophobic versus hydrophilic surfaces. When 4RepCT is placed in a wing arrangement model and periodically repeated on a hydrophobic surface, fi-sheet structures of the poly-alanine repeats are preserved, while the CT part is settled on top, presenting a fibril with a height of similar to 7 nm and a width of similar to 11 nm. Both atomic force microscopy and cryo-electron microscopy imaging support this model as a possible fibril formation on hydrophobic surfaces. These results contribute to the understanding of silk assembly and alignment mechanism onto hydrophobic surfaces.
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| 29. |
- Delavari, Najmeh, 1991-
(författare)
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Computational Modelling of Organic Bioelectronic Devices and Materials
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bioelectronics being the intersection field between electronics and biology, aims to investigate the transduction between electronic signals and ionic signals within a biological environment. Organic materials such as conducting polymers are extensively utilized in the fabrication and development of bioelectronic devices due to their ability to conduct both electrons and ions. In addition, organic materials offer advantages compared to their inorganic traditional counterparts, including being flexible, solution processable and printable as it is an easy strategy for the fabrication process. These unique properties make organic conductor materials a good match for a wide range of organic bioelectronic applications such as organic transistors and biosensors interacting with biological/physiological systems and pave the way for more developments in the in the state-of-the-art technology of organic bioelectronics. Many of the organic bioelectronic devices function in contact with a biological system, usually an electrolytic medium, where mostly ionic transport occurs. Therefore, understanding the structural, morphological, and electronic properties of materials and devices used for organic bioelectronics applications is the topic of strong current interest. This thesis is focused on two levels of computational investigations: studying bioelectronic devices and studying materials used for bioelectronic applications. The former includes modelling of electrolyte-gated organic field effect transistors (EGOFET), whereas the latter provides theoretical insights into morphological changes, ion injection, water intake, and self-assembly of conducting polymers. In the part of the thesis addressing the device modelling we first proposed an EGOFET model based on the Nernst-Planck-Poisson equations to describe, on equal footing, both the polymer and the electrolyte regions within the device. Using the developed model, we modelled and analysed experimentally measured current–voltage characteristics of the device (the output and transfer curves), where a semi-qualitative agreement between the experimental and calculated results was achieved. In a follow-up study, we demonstrated that Nernst-Planck-Poisson modelling represents a powerful tool allowing quantitative device design, modelling and analysis enabling us to forecast the influence of geometrical parameters as well as the materials used as electrolyte and the organic semiconductor for the case of a printed EGOFET. To explore the ion exchange phenomena at the interface of conducting polymers with aqueous electrolytes, we provided a detailed atomistic understanding of the water intake, swelling, and ion injection during cyclic voltammetry. By combining the molecular dynamics simulations with experimental measurements such as e-QCM (electrochemical quartz crystal microbalance), UV−VIS−NIR absorption spectroscopy, and XPS (X-ray photoelectron spectroscopy) we demonstrated that the PEDOT:Tos film underwent significant changes in morphology and mass during the redox processes. Finally, we studied the self-assembly of polythiophene based polymers with glycol and alkyl side chains deposited on the gold surface. Using molecular dynamics simulations, we investigated the diffusion of the molecules and analysed their conformations. We explored how different side chains interact with each other and how they influence the conjugated polymers self-assembly. We believe that the knowledge we acquired from our studies, combining experimental investigations with computational insights, provided an important understanding of the fundamental molecular processes at the material and device level that could help a practical enhancement in the field of organic bioelectronics.
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| 30. |
- Delavari, Najmeh, et al.
(författare)
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Water Intake and Ion Exchange in PEDOT:Tos Films upon Cyclic Voltammetry: Experimental and Molecular Dynamics Investigation
- 2021
-
Ingår i: Macromolecules. - : AMER CHEMICAL SOC. - 0024-9297 .- 1520-5835. ; 54:13, s. 6552-6562
-
Tidskriftsartikel (refereegranskat)abstract
- Conductive polymer PEDOT:Tos (3,4-ethylenedioxythiophene doped with molecular tosylate) gained considerable attention in various devices for bioelectronic applications, such as organic transistors and sensors. Many of these devices function upon oxidation/reduction processes in contact with aqueous electrolytes. So far, theoretical insight into morphological changes, ion injection, and water intake during these processes was rather limited. In the present work, we combined experiments and molecular dynamics simulations to study the water intake, swelling, and exchange of ions in the PEDOT:Tos film during cyclic voltammetry. We showed that the film underwent significant changes in morphology and mass during the redox processes. We observed both experimentally and in simulations that the film lost its mass during reduction, as tosylate and Na were expelled and gained mass during oxidation mainly due to the uptake of anions, i.e., tosylate and Cl. The results were in line with the UV-VIS-NIR absorption measurements and X-ray photoelectron spectroscopy (XPS) measurements, which revealed that during the redox process a portion of Tos was replaced by Cl- as the counterion for PEDOT. Also, the relative mass change between the most oxidized and reduced states was similar to 10 to 14% according to both experiments and simulations. We detected an overall material loss of the film during voltammetry cycles indicating that a portion of the material leaving the film during reduction did not return to the film during the consecutive oxidation. Our combined experimental/simulation study unraveled the underlying molecular processes in the PEDOT:Tos film upon the redox process, providing the essential understanding needed to improve and assess the performance of bioelectronic devices.
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| 31. |
- Di Meo, Florent, et al.
(författare)
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DNA electronic circular dichroism on the inter-base pair scale : An experimental-theoretical case study of the at homo-oligonucleotide
- 2015
-
Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 6:3, s. 355-359
-
Tidskriftsartikel (refereegranskat)abstract
- A successful elucidation of the near-ultraviolet electronic circular dichroism spectrum of a short double-stranded DNA is reported. Time-dependent density functional theory methods are shown to accurately predict spectra and assign bands on the microscopic base-pair scale, a finding that opens the field for using circular dichroism spectroscopy as a sensitive nanoscale probe of DNA to reveal its complex interactions with the environment. (Chemical Equation Presented).
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| 32. |
- Elie, Margaux, et al.
(författare)
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Designing NHC-Copper(I) Dipyridylamine Complexes for Blue Light-Emitting Electrochemical Cells
- 2016
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 8:23, s. 14678-14691
-
Tidskriftsartikel (refereegranskat)abstract
- This study presents the influence of various substituents on the photophysical features of heteroleptic copper(I) complexes bearing both N-heterocyclic carbene (NHC) and dipyridylamine (dpa = dipyridylamine skeleton corresponding to ligand L1) ligands. The luminescent properties have been compared to our recently reported archetypal blue emitting [Cu(IPr)(dpa)][PF6] complex. The choice of the substituents on both ligands has been guided to explore the effect of the electron donor/acceptor and "push-pull" on the emission wavelengths and photoluminescence quantum yields. A selection of the best candidates in terms of their photophysical features were applied for developing the first blue light emitting electrochemical cells (LECs) based on copper(I) complexes. The device analysis suggests that the main concern is the moderate redox stability of the complexes under high applied driving currents, leading to devices with moderate stabilities pointing to a proof-of-concept for further development. Nevertheless, under low applied driving currents the blue emission is stable, showing performance levels competitive to those reported for blue LECs baged on iridium(III) complexes. Overall, this work provides valuable guidelines to tackle the design of enhanced NHC copper complexes for lighting applications in the near future.
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| 33. |
- Elie, Margaux, et al.
(författare)
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Role of the Bridging Group in Bis-Pyridyl Ligands : Enhancing Both the Photo- and Electroluminescent Features of Cationic (IPr) Cu-I Complexes
- 2017
-
Ingår i: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 23:64, s. 16328-16337
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the benefits of changing the bridging group X of bis-pyridyl ligands, that is, Py-X-Py where X is NH, CH2, C(CH3)(2), or PPh, on the photo-and electroluminescent properties of a new family of luminescent cationic H-heterocyclic carbene (NHC) copper(I) complexes. A joint experimental and theoretical study demonstrates that the bridging group affects the molecular conformation from a planar-like structure (X is NH and CH2) to a boat-like structure (X is C(CH3)(2) and PPh), leading to i) four-fold enhancement of the photoluminescence quantum yield (phi(em)) without affecting the thermally activated delayed fluorescence mechanism, and ii) one order of magnitude reduction of the ionic conductivity (sigma) of thin films. This leads to an overall enhancement of the device efficacy and luminance owing to the increased phi(em) and the use of low applied driving currents.
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| 34. |
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| 35. |
- Gainar, Adrian, et al.
(författare)
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Tuning the Organogelating and Spectroscopic Properties of a C-3-Symmetric Pyrene-Based Gelator through Charge Transfer
- 2021
-
Ingår i: Chemistry - A European Journal. - : WILEY-V C H VERLAG GMBH. - 0947-6539 .- 1521-3765. ; 27:7, s. 2410-2420
-
Tidskriftsartikel (refereegranskat)abstract
- Two-component organogels and xerogels based on a C-3-symmetric pyrene-containing gelator have been deeply characterized through a wide range of techniques. Based on the formation of charge transfer complexes, the gelation phenomenon proved to be highly dependent on the nature of the electron poor dopant. This parameter significantly influenced the corresponding gelation domains, the critical gelation concentrations of acceptor dopants, the gel-to-sol transition temperatures, the microstructures formed in the xerogel state and their spectroscopic properties. In particular, titrations and variable-temperature UV-visible absorption spectroscopy demonstrated the key role of donor-acceptor interactions with a remarkable correlation between the phase transition temperatures and the disappearance of the characteristic charge transfer bands. The assignment of these electronic transitions was confirmed through time-dependent density functional theory (TD-DFT) calculations. Eventually, it was shown that the luminescent properties of these materials can be tuned with the temperature, either in intensity or emission wavelength.
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| 36. |
- Garg, Mohit, et al.
(författare)
-
Moisture uptake in nanocellulose : the effects of relative humidity, temperature and degree of crystallinity
- 2021
-
Ingår i: Cellulose. - : Springer Science and Business Media B.V.. - 0969-0239 .- 1572-882X. ; 28:14, s. 9007-9021
-
Tidskriftsartikel (refereegranskat)abstract
- Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of these materials need to be better understood for their use in biomedical and bioelectronics applications, in humidity sensing and thermal insulation. In this work, we present a combination of hybrid Grand Canonical Monte Carlo and Molecular Dynamics simulations and experimental measurements to investigate the moisture uptake within nanocellulose foams. To explore the effect of surface modification on moisture uptake we used two types of celluloses, namely TEMPO-oxidized cellulose nanofibrils and carboxymethylated cellulose nanofibrils. We find that the moisture uptake in both the cellulose nanomaterials increases with increasing relative humidity (RH) and decreases with increasing temperature, which is explained using the basic thermodynamic principles. The measured and calculated moisture uptake in amorphous cellulose (for a given RH or temperature) is higher as compared to crystalline cellulose with TEMPO- and CM-modified surfaces. The high water uptake of amorphous cellulose films is related to the formation of water-filled pores with increasing RH. The microscopic insight of water uptake in nanocellulose provided in this study can assist the design and fabrication of high-performance cellulose materials with improved properties for thermal insulation in humid climates or packaging of water sensitive goods. Graphic abstract: [Figure not available: see fulltext.]
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| 37. |
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| 38. |
- Garg, Mohit, et al.
(författare)
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Theoretical Rationalization of Self-Assembly of Cellulose Nanocrystals: Effect of Surface Modifications and Counterions
- 2020
-
Ingår i: Biomacromolecules. - : AMER CHEMICAL SOC. - 1525-7797 .- 1526-4602. ; 21:8, s. 3069-3080
-
Tidskriftsartikel (refereegranskat)abstract
- The hierarchical self-assembly of cellulose nanocrystals (CNCs) is an important phenomenon occurring naturally in plant cell walls. Utilization of this assembly for advanced applications requires a fundamental theoretical understanding of interactions between the CNCs, which is still incomplete. Hence, in this work, we used molecular dynamics simulations to study the effect of surface modification on the interactions between the CNCs and the resulting bundling process. We consider two types of common surface modifications of native CNCs, sulfated CNCs (SCNCs) and TEMPO-oxidized CNCs (TCNCs), in the presence of two types of counterions, Na+ and Ca2+, in solution. We used the umbrella sampling method to calculate the potential of the mean force (PMF), and we found that the strength of interaction between the modified CNCs decreases, compared with the native CNCs. The strength of interaction for TCNCs is almost similar to that for SCNCs at the same level of surface substitution, whereas the type of counterion has a strong effect on the PMF with a higher interaction energy between the CNCs in the presence of a divalent counterion as compared to a monovalent counterion. Finally, we studied the self-assembly of CNCs into a hexagonal bundle for the native CNCs and sulfated CNCs focusing on the twist of the bundle, bound water inside the bundle, inter-CNC gap, and interaction energy between the CNCs in the bundle, and the effect of the counterions on the morphology of the bundle. The equilibrium spacing of the CNCs within the bundle is found to be consistent with the results of PMF calculations for the minimum separation distance between the respective crystal surfaces.
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| 39. |
- Giannicchi, Ilaria, et al.
(författare)
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Orthohalogen substituents dramatically enhance hydrogen bonding of aromatic ureas in solution
- 2014
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Ingår i: Chemical Communications. - : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 50:5, s. 611-613
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Tidskriftsartikel (refereegranskat)abstract
- The phenylurea moiety is a ubiquitous synthon in supramolecular chemistry. Here we report that the introduction of chlorine or bromine atoms in the ortho positions to the urea unit is a simple and very efficient way to improve its intermolecular hydrogen bond (HB) donor character. This effect was demonstrated in solution both in the context of self-association of bis-ureas and hydrogen bonding of mono-ureas to strong HB acceptors.
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| 40. |
- Giobbio, Ginevra, et al.
(författare)
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Design Rule Hidden from The Eye in S/N-Bridged Ancillary Ligands for Copper(I) Complexes Applied to Light-Emitting Electrochemical Cells
- 2023
-
Ingår i: Advanced Functional Materials. - : WILEY-V C H VERLAG GMBH. - 1616-301X .- 1616-3028. ; 33:50
-
Tidskriftsartikel (refereegranskat)abstract
- Enhancing low-energy emitting Cu(I)-ionic transition metal complexes (iTMCs) light-emitting electrochemical cells (LECs) is of utmost importance towards Cu(I)-iTMC-based white-emitting LECs. Here, the ancillary ligand design includes (i) extension of & pi;-systems and (ii) insertion of S-bridge between heteroaromatics rings. This led to two novel heteroleptic Cu(I)-iTMCs: 2-(pyridin-2-yl-l2-azanyl)quinoline (CuN2) and 2-(naphthalen-2-ylthio)quinoline (CuS2) as N<^>N and bis[(2-diphenylphosphino)phenyl] ether as P<^>P, exhibiting improved photoluminescence quantum yields (& phi;) and thermally activated delayed fluorescence processes compared to their reference Cu(I)-iTMCs: di(pyridin-2-yl)-l2-azane (CuN1) and di(pyridin-2-yl)sulfane (CuS1). Despite CuS2 stands out with the highest & phi; (38% vs 17 / 14 / 1% for CuN1 / CuN2 / CuS1), only CuN2-LECs show the expected enhanced performance (0.35 cd A(-1) at luminance of 117 cd m(-2)) compared to CuN1-LECs (0.02 cd A(-1) at6 cd m(-2)), while CuS2-LECs feature low performances (0.04 cd A(-1) at 10 cd m(-2)). This suggests that conventional chemical design rules are not effective towards enhancing device performance. Herein, nonconventional multivariate statistical analysis and electrochemical impedance spectroscopy studies allow to rationalize the mismatch between chemical design and device performance bringing to light a hidden design rule: polarizability of the ancillary ligand is key for an efficient Cu(I)-iTMC-LECs. All-in-all, this study provides fresh insights for the design of Cu-iTMCs fueling research on sustainable ion-based lighting sources.
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| 41. |
- Gonzalez-Sanchez, Marina, et al.
(författare)
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Stacked or Folded? : Impact of Chelate Cooperativity on the Self-Assembly Pathway to Helical Nanotubes from Dinucleobase Monomers
- 2023
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 145:32, s. 17805-17818
-
Tidskriftsartikel (refereegranskat)abstract
- Self-assembled nanotubesexhibit impressive biologicalfunctionsthat have always inspired supramolecular scientists in their effortsto develop strategies to build such structures from small moleculesthrough a bottom-up approach. One of these strategies employs moleculesendowed with self-recognizing motifs at the edges, which can undergoeither cyclization-stacking or folding-polymerizationprocesses that lead to tubular architectures. Which of these self-assemblypathways is ultimately selected by these molecules is, however, oftendifficult to predict and even to evaluate experimentally. We showhere a unique example of two structurally related molecules substitutedwith complementary nucleobases at the edges (i.e., G:C and A:U) for which the supramolecular pathway takenis determined by chelate cooperativity, that is, by their propensityto assemble in specific cyclic structures through Watson-Crickpairing. Because of chelate cooperativities that differ in severalorders of magnitude, these molecules exhibit distinct supramolecularscenarios prior to their polymerization that generate self-assemblednanotubes with different internal monomer arrangements, either stackedor coiled, which lead at the same time to opposite helicities andchiroptical properties.
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| 42. |
- Gowda, Vasantha, et al.
(författare)
-
Structural characterisation of amyloid-like fibrils formed by an amyloidogenic peptide segment of β-lactoglobulin
- 2021
-
Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 11:45, s. 27868-27879
-
Tidskriftsartikel (refereegranskat)abstract
- Protein nanofibrils (PNFs) represent a promising class of biobased nanomaterials for biomedical and materials science applications. In the design of such materials, a fundamental understanding of the structure–function relationship at both molecular and nanoscale levels is essential. Here we report investigations of the nanoscale morphology and molecular arrangement of amyloid-like PNFs of a synthetic peptide fragment consisting of residues 11–20 of the protein β-lactoglobulin (β-LG11–20), an important model system for PNF materials. Nanoscale fibril morphology was analysed by atomic force microscopy (AFM) that indicates the presence of polymorphic self-assembly of protofilaments. However, observation of a single set of 13C and 15N resonances in the solid-state NMR spectra for the β-LG11–20 fibrils suggests that the observed polymorphism originates from the assembly of protofilaments at the nanoscale but not from the molecular structure. The secondary structure and inter-residue proximities in the β-LG11–20 fibrils were probed using NMR experiments of the peptide with 13C- and 15N-labelled amino acid residues at selected positions. We can conclude that the peptides form parallel β-sheets, but the NMR data was inconclusive regarding inter-sheet packing. Molecular dynamics simulations confirm the stability of parallel β-sheets and suggest two preferred modes of packing. Comparison of molecular dynamics models with NMR data and calculated chemical shifts indicates that both packing models are possible.
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| 43. |
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| 44. |
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| 45. |
- Gustafsson, Camilla, et al.
(författare)
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Deciphering the Electronic Transitions of Thiophene-Based Donor-Acceptor-Donor Pentameric Ligands Utilized for Multimodal Fluorescence Microscopy of Protein Aggregates
- 2021
-
Ingår i: ChemPhysChem. - : Wiley-VCH Verlag. - 1439-4235 .- 1439-7641. ; 22:3, s. 323-335
-
Tidskriftsartikel (refereegranskat)abstract
- Anionic pentameric thiophene acetates can be used for fluorescence detection and diagnosis of protein amyloid aggregates. Replacing the central thiophene unit by benzothiadiazole (BTD) or quinoxaline (QX) leads to large emission shifts and basic spectral features have been reported [Chem. Eur. J. 2015, 21, 15133-13137]. Here we present new detailed experimental results of solvent effects, time-resolved fluorescence and examples employing multi-photon microscopy and lifetime imaging. Quantum chemical response calculations elucidate how the introduction of the BTD/QX groups changes the electronic states and emissions. The dramatic red-shift follows an increased conjugation and quinoid character of the π-electrons of the thiophene backbone. An efficient charge transfer in the excited states S1 and S2 compared to the all-thiophene analogue makes these more sensitive to the polarity and quenching by the solvent. Taken together, the results guide in the interpretation of images of stained Alzheimer disease brain sections employing advanced fluorescence microscopy and lifetime imaging, and can aid in optimizing future fluorescent ligand development.
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| 46. |
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| 47. |
- Gustafsson, Camilla, et al.
(författare)
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Quantum Mechanics/Molecular Mechanics Density Functional Theory Simulations of the Optical Properties Fingerprinting the Ligand-Binding of Pentameric Formyl Thiophene Acetic Acid in Annyloid-beta(1-42)
- 2020
-
Ingår i: Journal of Physical Chemistry A. - : AMER CHEMICAL SOC. - 1089-5639 .- 1520-5215. ; 124:5, s. 875-888
-
Tidskriftsartikel (refereegranskat)abstract
- The binding pocket proposed by Konig et al. [Chem. Commun. 2018, 54, 3030-3033] for the biomarker pentameric formyl thiophene acetic acid (p-FTAA) in the fibrillar structure of amyloid-beta(1-42) has been put to the test by the comparison of theoretical and experimental optical absorption and fluorescence spectra obtained in a water environment and inside the protein scaffold. The optical absorption/emission properties of this luminescent conjugated oligothiophene were studied by means of classical force field molecular dynamics simulations to account for the sampling of configuration space in conjunction with polarizable embedding time-dependent density functional theory calculations of spectra. The nuclear motions of residues in the beta-sheet were found to be modest, and the time dependence of embedding parameters was shown to be negligible so that a time-independent parameter set could be derived and used for all 300 snapshots considered in the spectrum averaging. In regard to linear absorption spectra, the calculated red shift due to protein binding for the dominant S-1 <- S-0 transition in p-FTAA was found to be equal to 23 nm (0.17 eV), which is in excellent agreement with the corresponding experimental result of 18 nm and taken as corroborating evidence for having correctly identified the binding pocket of p-FTAA in the amyloid. The underlying mechanisms for the calculated red shift were disentangled, and it is shown that some 20 nm (0.15 eV) of the total 23 nm (0.17 eV) is associated with increased planarity of p-FTAA in the binding pocket, whereas a mere 3 nm (0.02 eV) is associated with changes in the environment. In regard to emission spectra, we demonstrate that intersystem crossing from the excited S-1 state to the triplet manifold of states is a less likely event for p-FTAA in the binding pocket as compared to in the aqueous solution, and we thereby partly explain the much higher quantum yield of fluorescence for the more rigid p-FTAA in the binding pocket. Two-photon absorption in p-FTAA is shown to predominantly occur to an overall symmetric excited state and be more than twice as strong for the biomarker in the binding pocket as compared to in water. The corresponding red shift, on the other hand, is very small. Earlier experimental two-photon fluorescence imaging using p-FTAA is shown not to target the dominant two-photon state, and ways to reach a higher image quality (lower signal-to-noise ratio) are proposed in terms of tuning the laser wavelength toward the region of 600 nm or the synthesis of asymmetric ligands with S-1 states that are both one- and two-photon allowed.
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| 48. |
- Hayton, James, et al.
(författare)
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Pi-Conjugated Molecular Nanowire Stacks Investigated by Frequency-Modulation Atomic Force Microscopy in the qPlus Configuration
- 2009
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Ingår i: APPLIED PHYSICS EXPRESS. - 1882-0778. ; 2:9, s. 091501-
-
Tidskriftsartikel (refereegranskat)abstract
- Self-assembled pi-conjugated nanowire stacks were imaged using a tuning-fork probe mounted in the qPlus configuration in frequency modulation mode under ultrahigh vacuum. High resolution topographic and dissipation images demonstrate the applicability of such probes to soft conjugated materials, with sub-molecular resolution achieved perpendicular to the stacking axis. A new insight is gained from the damping contrast into the local mechanical properties of edge-on pi-conjugated stacks.
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| 49. |
- Iavicoli, P., et al.
(författare)
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Tuning the supramolecular chirality of one-and two-dimensional aggregates with the number of stereogenic centers in the component porphyrins
- 2010
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 132:27, s. 9350-9362
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Tidskriftsartikel (refereegranskat)abstract
- A synthetic strategy was developed for the preparation of porphyrins containing between one and four stereogenic centers, such that their molecular weights vary only as a result of methyl groups which give the chiral forms. The low-dimensional nanoscale aggregates of these compounds Reveal the profound effects of this varying molecular chirality on their supramolecular structure and optical activity. The number of stereogenic centers influences significantly the self-assembly and chiral structure of the aggregates of porphyrin molecules described here. A scanning tunneling microscopy study of monolayers on graphite shows that the degree of structural chirality with respect to the surface increases almost linearly with the number of stereogenic centers, and only one handedness is formed in the monolayers, whereas the achiral compound forms a mixture of mirror-image domains at the surface. In solution, four hydrogen bonds induce the formation of an H-aggregate, and circular dichroism measurements and theoretical studies indicate that the compounds self-assemble into helical structures. Both the chirality and stability of the aggregates depend critically on the number of stereocenters. The chiral porphyrin derivatives gelate methylcyclohexane at concentrations dependent on the number and position of chiral groups at the periphery of the aromatic core, reflecting the different aggregation forces of the molecules in solution. Increasing the number of stereogenic centers requires more material to immobilize the solvent, in all likelihood because of the greater solubility of the porphyrins. The vibrational circular dichroism spectra of the gels show that all compounds have a chiral environment around the amide bonds, confirming the helical model proposed by calculations. The morphologies of the xerogels (studied by scanning electron microscopy and scanning force microscopy) are similar, although more fibrous features are present in the molecules with fewer stereogenic centers. Importantly, the presence of only one stereogenic center, bearing a methyl group as the desymmetrizing ligand, in a molecule of considerable molecular weight is enough to induce singlehanded chirality in both the one-and two-dimensional supramolecular self-assembled structures.
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- Isare, B., et al.
(författare)
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Engineering the cavity of self-assembled dynamic nanotubes
- 2009
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 113:11, s. 3360-3364
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Tidskriftsartikel (refereegranskat)abstract
- By analogy with hydrogen-bonded molecular capsules, self-assembled nanotubes are of interest because they can temporarily isolate guest molecules from the solution. We show here that the stability of a particular bis-urea based dynamic self-assembled nanotube is related to the possibility for solvent molecules to fit inside the tubular cavity. The diameter of the cavity can be finely tuned by introducing a modified monomer in controlled amount.
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