Topic
Conformational isomerism
About: Conformational isomerism is a research topic. Over the lifetime, 11563 publications have been published within this topic receiving 199312 citations.
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TL;DR: Partially resolved ultraviolet rotational band contours associated with the S1 ← S0 origin bands of the six most populated conformers of jet-cooled phenylalanine have been recorded via resonant two-photon ionization as mentioned in this paper.
Abstract: Partially resolved ultraviolet rotational band contours associated with the S1 ← S0 origin bands of the six most populated conformers of jet-cooled phenylalanine have been recorded via resonant two-photon ionization. The strong dependence of their transition moment orientation on the conformation of the alanyl side chain has facilitated their structural assignment through simulations based upon ab initio computation. The S1 lifetimes of all six conformers, measured through pump−probe delayed ionization, reveal an efficient nonradiative decay pathway in the most stable conformer, which is stabilized through a chain of intramolecular hydrogen bonds linking the side chain to the benzene ring.
64 citations
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TL;DR: In this paper, the structure and energy of the four lowest energy conformers of glycine were determined at the MP2/aug-cc-pVDZ level of theory, and the optimized structural parameters for these conformers agree with previous theoretical results obtained by highly correlated ab initio methods and with available experimental data.
Abstract: The structure and energetics of the four lowest-energy conformers of glycine were determined at the MP2/aug-cc-pVDZ level of theory. The optimized structural parameters for these conformers agree with previous theoretical results obtained by highly correlated ab initio methods and with available experimental data. The only structure with planar heavy atom arrangement is conformer I (global minimum), the other conformers have nonplanar heavy atom arrangements. In accordance with temperature dependence studies of the vibrational spectra in various rare gas environments, conformers III and IV have small interconversion barriers to conformer I (940 and 740 cm−1). Our calculations have shown that full-dimensional anharmonic treatment is required for an accurate description of the vibrational modes in various glycine conformers. The most pronounced effect has been observed for conformer II with the intramolecular O–H⋅⋅⋅N bond. The theoretical results obtained at the MP2/aug-cc-pVDZ level reproduce quantitatively the argon matrix experiments. The calculation uses the quartic force field approximation in the framework of second-order perturbation theory. An estimate of the higher-order correction is also given.
64 citations
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TL;DR: These benchmark results show that hydrogen bonding can terminate proton tunneling reactions and efficiently stabilize intrinsically unstable conformational structures in complex asymmetrical hydrogen-bonded networks.
Abstract: We studied hydrogen bonding between formic acid (FA) and water in solid argon and identified the first water complex with the higher-energy conformer cis-FA. In sharp contrast to cis-FA monomer, cis-FA interacting with water is very stable at low temperatures, which was explained by strong O-H...O hydrogen bonding. These benchmark results show that hydrogen bonding can terminate proton tunneling reactions and efficiently stabilize intrinsically unstable conformational structures in complex asymmetrical hydrogen-bonded networks. This general effect occurs when the energy difference between conformers is smaller than the hydrogen bond interaction energy, which opens perspectives in chemistry on intrinsically unstable conformers.
64 citations
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64 citations
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TL;DR: In this article, rotamerization and UV photochemical decomposition of oxalic acid were studied in various matrices and ab initio calculations in this paper were performed. And two conformers, cTc and cTt, and their conversion energy from one form to the other were observed and studied.
Abstract: Rotamerization and UV photochemical decomposition of oxalic acid were studied in various matrices and ab initio calculations in this paper. Two conformers, cTc (2 intramolecular hydrogen bonds) and cTt (one intramolecular hydrogen bond) and their conversion energy from one form to the other were observed and studied. Full Xe arc irradiation decomposes matrix oxalic acid. For 6 oxalic acid conformers other spectra are calculated and assigned along with their potential energy distributions. 25 refs., 8 figs., 11 tabs.
64 citations