| 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. |
- 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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| 4. |
- 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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| 5. |
- Cornelissen, Tim, et al.
(författare)
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Kinetic Monte Carlo simulations of organic ferroelectrics
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 21:3, s. 1375-1383
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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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| 6. |
- 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
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Ingår i: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 6:3, s. 355-359
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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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| 7. |
- 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
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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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| 8. |
- 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
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Ingår i: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 23:64, s. 16328-16337
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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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| 9. |
- Kastinen, Tuuva, et al.
(författare)
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Electronic couplings and rates of excited state charge transfer processes at poly(thiophene-co-quinoxaline)-PC71BM interfaces: two- versus multi-state treatments
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 21:46, s. 25606-25625
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Tidskriftsartikel (refereegranskat)abstract
- Electronic coupling between adjacent molecules is one of the key parameters determining the charge transfer (CT) rates in bulk heterojunction (BHJ) polymer solar cells (PSCs). We calculate theoretically electronic couplings for exciton dissociation (ED) and charge recombination (CR) processes at local poly(thiophene-co-quinoxaline) (TQ)-PC71BM interfaces. We use eigenstate-based coupling schemes, i.e. the generalized Mulliken-Hush (GMH) and fragment charge difference (FCD) schemes, including 2 to multiple (3-11) states. Moreover, we study the effects of functionals, excited state methods, basis sets, surrounding media, and relative placements of TQ and PC71BM on the coupling values. Generally, both schemes provide consistent couplings with the global hybrid functionals, which yield more charge-localized diabatic states and constant coupling values regardless of the number of states, and so the 2-state schemes may be sufficient. The (non-tuned and optimally tuned) long-range corrected (LRC) functionals result in more notable mixing of the local components with the CT states. Employing multiple states reduces the mixing and thus improves the LRC results, although the method still affects the GMH CR couplings. As the FCD scheme is less sensitive, we recommend combining it with the multi-state treatment for polymer-fullerene systems when using the LRC functionals. Finally, we employ the 11-state FCD couplings to calculate the ED and CR rates, which are consistent with the experimental rates of the polymer-fullerene systems. Our results provide more insight into choosing a suitable eigenstate-based coupling scheme for predicting the electronic couplings and CT rates in photoactive systems.
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| 10. |
- Kottravel, Sathish, et al.
(författare)
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Visual Analysis of Charge Flow Networks for Complex Morphologies
- 2019
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Ingår i: Computer graphics forum (Print). - : WILEY. - 0167-7055 .- 1467-8659. ; 38:3, s. 479-489
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Tidskriftsartikel (refereegranskat)abstract
- In the field of organic electronics, understanding complex material morphologies and their role in efficient charge transport in solar cells is extremely important. Related processes are studied using the Ising model and Kinetic Monte Carlo simulations resulting in large ensembles of stochastic trajectories. Naive visualization of these trajectories, individually or as a whole, does not lead to new knowledge discovery through exploration. In this paper, we present novel visualization and exploration methods to analyze this complex dynamic data, which provide succinct and meaningful abstractions leading to scientific insights. We propose a morphology abstraction yielding a network composed of material pockets and the interfaces, which serves as backbone for the visualization of the charge diffusion. The trajectory network is created using a novel way of implicitly attracting the trajectories to the skeleton of the morphology relying on a relaxation process. Each individual trajectory is then represented as a connected sequence of nodes in the skeleton. The final network summarizes all of these sequences in a single aggregated network. We apply our method to three different morphologies and demonstrate its suitability for exploring this kind of data.
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