| 1. |
- Augusto Berrocal, Jose, et al.
(author)
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Consequences of conformational flexibility in hydrogen-bond-driven self-assembly processes
- 2016
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In: Chemical Communications. - : ROYAL SOC CHEMISTRY. - 1359-7345 .- 1364-548X. ; 52:72, s. 10870-10873
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Journal article (peer-reviewed)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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| 2. |
- Di Meo, Florent, et al.
(author)
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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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In: The Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 6:3, s. 355-359
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Journal article (peer-reviewed)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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| 3. |
- Di Meo, Florent, et al.
(author)
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Unraveling the performance of dispersion-corrected functionals for the accurate description of weakly bound natural polyphenols
- 2015
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In: Journal of Molecular Modeling. - : SPRINGER. - 1610-2940 .- 0948-5023. ; 21:11, s. 291-
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Journal article (peer-reviewed)abstract
- Long-range non-covalent interactions play a key role in the chemistry of natural polyphenols. We have previously proposed a description of supramolecular polyphenol complexes by the B3P86 density functional coupled with some corrections for dispersion. We couple here the B3P86 functional with the D3 correction for dispersion, assessing systematically the accuracy of the new B3P86-D3 model using for that the well-known S66, HB23, NCCE31, and S12L datasets for non-covalent interactions. Furthermore, the association energies of these complexes were carefully compared to those obtained by other dispersion-corrected functionals, such as B(3) LYP-D3, BP86-D3 or B3P86-NL. Finally, this set of models were also applied to a database composed of seven non-covalent polyphenol complexes of the most interest.
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| 4. |
- Elie, Margaux, et al.
(author)
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Designing NHC-Copper(I) Dipyridylamine Complexes for Blue Light-Emitting Electrochemical Cells
- 2016
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In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 8:23, s. 14678-14691
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Journal article (peer-reviewed)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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| 5. |
- Elie, Margaux, et al.
(author)
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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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In: Chemistry - A European Journal. - : Wiley-VCH Verlagsgesellschaft. - 0947-6539 .- 1521-3765. ; 23:64, s. 16328-16337
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Journal article (peer-reviewed)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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| 6. |
- Fourre, Isabelle, et al.
(author)
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Dimerization of quercetin, Diels-Alder vs. radical-coupling approach: a joint thermodynamics, kinetics, and topological study
- 2016
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In: Journal of Molecular Modeling. - : SPRINGER. - 1610-2940 .- 0948-5023. ; 22:8, s. 190-
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Journal article (peer-reviewed)abstract
- Quercetin is a prototypical antioxidant and prominent member of flavonoids, a large group of natural polyphenols. The oxidation of quercetin may lead to its dimerization, which is a paradigm of the more general polyphenol oligomerization. There exist two opposing mechanisms to describe the dimerization process, namely radical-coupling or Diels-Alder reactions. This work presents a comprehensive rationalization of this dimerization process, acquired from density functional theory (DFT) calculations. It is found that the two-step radical-coupling pathway is thermodynamically and kinetically preferred over the Diels-Alder reaction. This is in agreement with the experimental results showing the formation of only one isomer, whereas the Diels-Alder mechanism would yield two isomers. The evolution in bonding, occurring during these two processes, is investigated using the atoms in molecules (AIM) and electron localization function (ELF) topological approaches. It is shown that some electron density is accumulated between the fragments in the transition state of the radical-coupling reaction, but not in the transition state of the Diels-Alder process.
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| 7. |
- Marion, Ronan, et al.
(author)
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NHC Copper(I) Complexes Bearing Dipyridylamine Ligands: Synthesis, Structural, and Photoluminescent Studies
- 2014
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In: Inorganic Chemistry. - : American Chemical Society. - 0020-1669 .- 1520-510X. ; 53:17, s. 9181-9191
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Journal article (peer-reviewed)abstract
- We describe the synthesis of new cationic tricoordinated copper complexes bearing bidentate pyridine-type ligands and N-heterocyclic carbene as ancillary ligands. These cationic copper complexes were fully characterized by NMR, electrochemistry, X-ray analysis, and photophysical studies in different environments. Density functional theory calculations were also undertaken to rationalize the assignment of the electronic structure and the photophysical properties. These tricoordinated cationic copper complexes possess a stabilizing CH-pi interaction leading to high stability in both solid and liquid states. In addition, these copper complexes, bearing dipyridylamine ligands having a central nitrogen atom as potential anchoring point, exhibit very interesting luminescent properties that render them potential candidates for organic light-emitting diode applications.
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| 8. |
- Novotna, M., et al.
(author)
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Cis-trans isomerization of silybins A and B
- 2014
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In: Beilstein Journal of Organic Chemistry. - : Beilstein-Institut. - 2195-951X .- 1860-5397. ; 10, s. 1047-1063
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Journal article (peer-reviewed)abstract
- Methods were developed and optimized for the preparation of the 2,3-cis- and the 10,11-cis-isomers of silybin by the Lewis acid catalyzed (BF 3-OEt2) isomerization of silybins A (1a) and B (1b) (trans-isomers). The absolute configuration of all optically pure compounds was determined by using NMR and comparing their electronic circular dichroism data with model compounds of known absolute configurations. Mechanisms for cis - trans-isomerization of silybin are proposed and supported by quantum mechanical calculations. © 2014 Novotná et al; licensee Beilstein-Institut.
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| 9. |
- Oliveras-González, C., et al.
(author)
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Bottom-Up Hierarchical Self-Assembly of Chiral Porphyrins through Coordination and Hydrogen Bonds
- 2015
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 137:50, s. 15795-15808
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Journal article (peer-reviewed)abstract
- A series of chiral synthetic compounds is reported that shows intricate but specific hierarchical assembly because of varying positions of coordination and hydrogen bonds. The evolution of the aggregates (followed by absorption spectroscopy and temperature-dependent circular dichroism studies in solution) reveal the influence of the proportion of stereogenic centers in the side groups connected to the chromophore ring in their optical activity and the important role of pyridyl groups in the self-assembly of these chiral macrocycles. The optical activity spans 2 orders of magnitude depending on composition and constitution. Two of the aggregates show very high optical activity even though the isolated chromophores barely give a circular dichroism signal. Molecular modeling of the aggregates, starting from the pyridine-zinc(II) porphyrin interaction and working up, and calculation of the circular dichroism signal confirm the origin of this optical activity as the chiral supramolecular organization of the molecules. The aggregates show a broad absorption range, between approximately 390 and 475 nm for the transitions associated with the Soret region alone, that spans wavelengths far more than the isolated chromophore. The supramolecular assemblies of the metalloporphyrins in solution were deposited onto highly oriented pyrolitic graphite in order to study their hierarchy in assembly by atomic force microscopy. Zero and one-dimensional aggregates were observed, and a clear dependence on deposition temperature was shown, indicating that the hierarchical assembly took place largely in solution. Moreover, scanning electron microscopy images of porphyrins and metalloporphyrins precipitated under out-of-equilibrium conditions showed the dependence of the number and position of chiral amide groups in the formation of a fibrillar nanomaterial. The combination of coordination and hydrogen bonding in the complicated assembly of these molecules-where there is a clear hierarchy for zinc(II)-pyridyl interaction followed by hydrogen-bonding between amide groups, and then van der Waals interactions-paves the way for the preparation of molecular materials with multiple chromophore environments.
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| 10. |
- Osella, Silvio, et al.
(author)
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Combining (Non)linear Optical and Fluorescence Analysis of DiD To Enhance Lipid Phase Recognition
- 2018
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In: Journal of Chemical Theory and Computation. - : AMER CHEMICAL SOC. - 1549-9618 .- 1549-9626. ; 14:10, s. 5350-5359
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Journal article (peer-reviewed)abstract
- The widespread interest in phase recognition of lipid membranes has led to the use of different optical techniques to enable differentiation of healthy and not fully functional cells. In this work, we show how the combination of different (non)linear optical methods such as one-photon absorption (OPA), two-photon absorption (TPA), and second harmonic generation (SHG) as well as the study of the fluorescence decay time leads to an enhanced screening of membrane phases using a fluorescent 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiD) probe. In the current study we consider the pure liquid disordered phases of DOPC (dioleoyl-sn-glycero-3-phosphocholine, room temperature) and DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 323 K), the solid gel phase of DPPC (298 K), and the liquid ordered phase of a 2:1 binary mixture of sphingomyelin and cholesterol. By means of extensive hybrid quantum mechanics molecular mechanics calculations and based upon the (non)linear absorption of the embedded probes, it is found that DiD can be used to identify the lipid bilayer phase. The joint TPA and SHG as well as fluorescence analyses qualifies DiD as a versatile probe for phase recognition. In particular, the SHG data obtained by means of hyper-Rayleigh scattering and by electric field induced second harmonic generation reveal differences in polarization of the probe in the different environments. The TPA results finally confirm the particular location of the probe in between the polar headgroup region of the 2:1 SM:Chol mixture in the liquid ordered phase.
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