On the Inter-Ring Torsion Potential of 2,2′-Bithiophene: A Review of Open Problems and Current Proposals

Guskova, Olga

doi:10.1007/978-3-319-50255-7_13

Cited by 3 publications

(2 citation statements)

References 121 publications

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“…Computational and theoretical analyses have been utilized along with experimental methods to study electronic and optical properties of both thiophene- and furan-based materials. ,− A significant amount of research focuses on short oligomers (made up of as few as two or three heterocycles), which allows researchers to probe structural properties and torsional profiles of these systems in greater detail. ,,,,− Density functional theory (DFT) techniques are frequently used to characterize these short oligomers, often after calibrating the DFT methods against experimental or ab initio quantum mechanical electronic structure methods. Some of the most rigorous studies have used coupled-cluster methods, such as CCSD, CCSD(T), and even CCSDT, to characterize the torsional profiles of the smallest oligomers with only two rings.…”

Section: Introductionmentioning

confidence: 99%

Torsional Profiles of Thiophene and Furan Oligomers: Probing the Effects of Heterogeneity and Chain Length

2021

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A systematic analysis of the torsional profiles of 55 unique oligomers composed of two to four thiophene and/or furan rings (n = 2 to 4) has been conducted using three density functional theory (DFT) methods along with MP2 and three different coupled-cluster methods. Two planar or quasiplanar minima were identified for each n = 2 oligomer system. In every case, the torsional angle (τ) between the heteroatoms about the carbon−carbon bond connecting the two rings is at or near 180°for the global minimum and 0°for the local minimum, referred to as anti and syn conformations, respectively. These oligomers have rotational barrier heights ranging from ca. 2 kcal mol −1 for 2,2′-bithiophene to 4 kcal mol −1 for 2,2′-bifuran, based on electronic energies computed near the CCSD(T) complete basis set (CBS) limit. The corresponding rotational barrier for the heterogeneous 2-(2-thienyl)furan counterpart falls approximately halfway between those values. The energy differences between the minima are approximately 2 and 0.4 kcal mol −1 for the homogeneous 2,2′-bifuran and 2,2′-bithiophene, respectively, whereas the energy difference between the planar local and global minima (at τ = 0 and 180°, respectively) is only 0.3 kcal mol −1 for 2-(2-thienyl)furan. Extending these three oligomers by adding one or two additional thiophene and/or furan rings resulted in only minor changes to the torsional profiles when rotating around the same carbon−carbon bond as the two-ring profiles. Relative energy differences between the syn and anti conformations were changed by no more than 0.4 kcal mol −1 for the corresponding n = 3 and 4 oligomers, while the rotational barrier height increased by no more than 0.8 kcal mol −1 .

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Section: Introductionmentioning

confidence: 99%

Torsional Profiles of Thiophene and Furan Oligomers: Probing the Effects of Heterogeneity and Chain Length

2021

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“…The bithiophene unit also helps maintain a high level of current in the BT-Azo molecular junction compared to a fully saturated n-alkyl spacer with the same length [14]. In addition, the bithiophene segment promotes possible stacking interactions in the molecular junction layer and endows the molecule with more conformational rigidity [51], as suggested by Lenfant and colleagues. The abbreviations Azo and BT stand for azobenzene and bithiophene, respectively.…”

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confidence: 92%

Photo-Programmable Processes in Bithiophene–Azobenzene Monolayers on Gold Probed via Simulations

Savchenko,

Hadjab,

Pavlov

et al. 2023

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In this study, we investigate the structural changes, electronic properties, and charge redistribution within azo-bithiophene (Azo-BT)-chemisorbed monolayers under different light stimuli using the density functional theory and molecular dynamics simulations. We consider two types of switches, Azo-BT and BT-Azo, with different arrangements of the Azo and BT blocks counting from the anchor thiol group. The chemisorbed monolayers of pure cis- and trans-isomers with a surface concentration of approximately 2.7 molecules per nm2 are modeled on a gold surface using the classical all-atom molecular dynamics. Our results reveal a significant shrinkage of the BT-Azo layer under UV illumination, whereas the thicknesses of the Azo-BT layer remain comparable for both isomers. This difference in behavior is attributed to the ordering of the trans-molecules in the layers, which is more pronounced for Azo-BT, leading to a narrow distribution of the inclination angle to the gold surface. Conversely, both layers consisting of cis-switches exhibit disorder, resulting in similar brush heights. To study charge transfer within the immobilized layers, we analyze each snapshot of the layer and calculate the mean charge transfer integrals using Nelsen’s algorithm for a number of interacting neighboring molecules. Combining these integrals with reorganization energies defined for the isolated molecules, we evaluate the charge transfer rates and mobilities for electron and hole hopping within the layers at room temperature based on Marcus’ theory. This research offers new perspectives for the innovative design of electrode surface modifications and provides insights into controlling charge transfer within immobilized layers using light triggers. Additionally, we identify molecular properties that are enhanced via specific molecular design, which contributes to the development of more efficient molecular switches for various electronic applications.

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Developing accurate intramolecular force fields for conjugated systems through explicit coupling terms

2018

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The accuracy of molecular mechanics force fields (FF) reveals critical for applications where precise molecular structures along a conformational sampling are required, as in the simulation of electronic spectroscopies. This implies abandoning generalized FFs in favor of specific FFs, with non-transferable parameters able to accurately describe the targeted species. A promising strategy in this direction consists in the so-called quantum mechanically derived FFs, in which the parameters are fitted onto reference data computed through quantum chemistry. However, in order to obtain a global set of parameters able to reliably describe the reference potential energy surface in different regions of the conformational space, the complexity of the analytical expressions of the FF becomes crucial. Regarding intramolecular interactions, the functional form of standard transferable FFs is restricted to terms that depend on only one internal coordinate. It will be shown that such models may reveal insufficient to describe systems as polyenic chains, where complex electronic effects, e.g. conjugation, intrinsically couple different ICs. We propose a functional form for intramolecular FFs, which includes explicit couplings between flexible dihedrals and stiff ICs (bonds and angles), being able to properly describe the geometrical changes arising not only from steric interactions, but also from conjugation effects, i.e. the change of bond orders induced by conformational changes. The parameterization of the coupled FFs is carried out by means of automated and efficient computational

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On the Inter-Ring Torsion Potential of 2,2′-Bithiophene: A Review of Open Problems and Current Proposals

Cited by 3 publications

References 121 publications

Torsional Profiles of Thiophene and Furan Oligomers: Probing the Effects of Heterogeneity and Chain Length

Torsional Profiles of Thiophene and Furan Oligomers: Probing the Effects of Heterogeneity and Chain Length

Photo-Programmable Processes in Bithiophene–Azobenzene Monolayers on Gold Probed via Simulations

Developing accurate intramolecular force fields for conjugated systems through explicit coupling terms

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