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Keywords = unsaturated dinitriles

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18 pages, 4741 KiB  
Article
A DFT Study on the Excited Electronic States of Cyanopolyynes: Benchmarks and Applications
by Marcin Gronowski and Robert Kołos
Molecules 2022, 27(18), 5829; https://doi.org/10.3390/molecules27185829 - 8 Sep 2022
Cited by 5 | Viewed by 2539
Abstract
Highly unsaturated chain molecules are interesting due to their potential application as nanowires and occurrence in interstellar space. Here, we focus on predicting the electronic spectra of polyynic nitriles HC2m+1N (m = 0–13) and dinitriles NC2n [...] Read more.
Highly unsaturated chain molecules are interesting due to their potential application as nanowires and occurrence in interstellar space. Here, we focus on predicting the electronic spectra of polyynic nitriles HC2m+1N (m = 0–13) and dinitriles NC2n+2N (n = 0–14). The results of time-dependent density functional theory (TD-DFT) calculations are compared with the available gas-phase and noble gas matrix experimental data. We assessed the performance of fifteen functionals and five basis sets for reproducing (i) vibrationless electronic excitation energies and (ii) vibrational frequencies in the singlet excited states. We found that the basis sets of at least triple-ζ quality were necessary to describe the long molecules with alternate single and triple bonds. Vibrational frequency scaling factors are similar for the ground and excited states. The benchmarked spectroscopic parameters were shown to be acceptably reproduced with adequately chosen functionals, in particular ωB97X, CAM-B3LYP, B3LYP, B971, and B972. Select functionals were applied to study the electronic excitation of molecules up to HC27N and C30N2. It is demonstrated that optical excitation leads to a shift from the polyyne- to a cumulene-like electronic structure. Full article
(This article belongs to the Special Issue Advances in Computational Spectroscopy)
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14 pages, 606 KiB  
Article
Homoconjugation vs. Exciton Coupling in Chiral α,β-Unsaturated Bicyclo[3.3.1]nonane Dinitrile and Carboxylic Acids
by Gintautas Bagdžiūnas, Eugenijus Butkus and Sigitas Stončius
Molecules 2014, 19(7), 9893-9906; https://doi.org/10.3390/molecules19079893 - 8 Jul 2014
Cited by 4 | Viewed by 7439
Abstract
The chiroptical properties of enantiomerically pure bicyclo[3.3.1]nona-2,6-diene-2,6-dicarbonitrile and related acids were studied by circular dichroism spectroscopy and theoretical computations. A consideration of the molecular structure of the synthesized difunctional compounds revealed that chromophores are predisposed to transannular through-space interaction due to a favourable [...] Read more.
The chiroptical properties of enantiomerically pure bicyclo[3.3.1]nona-2,6-diene-2,6-dicarbonitrile and related acids were studied by circular dichroism spectroscopy and theoretical computations. A consideration of the molecular structure of the synthesized difunctional compounds revealed that chromophores are predisposed to transannular through-space interaction due to a favourable conformation of the bicyclic skeleton and a rather small interchromophoric distance. Evidence for non-exciton-type coupling between the two acrylonitrile and acrylate moieties in 3 and 4, respectively, was obtained by chiroptical spectroscopy and DFT calculations. Full article
(This article belongs to the Special Issue Dynamic Stereochemistry)
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10 pages, 193 KiB  
Article
An Efficient Chemoselective Reduction of Furan Series Unsaturated Dinitriles
by Pavel Bobal and Janette Bobalova
Molecules 2013, 18(2), 2212-2221; https://doi.org/10.3390/molecules18022212 - 11 Feb 2013
Cited by 9 | Viewed by 7207
Abstract
An efficient reduction of double bonds conjugated with nitrile groups and acid or base sensitive furan rings with 2-phenylbenzimidazoline generated in situ has been successfully accomplished with high yields and excellent selectivity. The employed reducing agent was prepared in one step from ordinary [...] Read more.
An efficient reduction of double bonds conjugated with nitrile groups and acid or base sensitive furan rings with 2-phenylbenzimidazoline generated in situ has been successfully accomplished with high yields and excellent selectivity. The employed reducing agent was prepared in one step from ordinary chemicals. The other advantages of the presented method include mild and convenient reaction conditions, a benign and cost effective reagent, simple work-up and separation of the products. As this process does neither affect cyano and nitro groups nor furan rings, it is a valuable alternative when metal-catalyzed hydrogenations or borohydride reductions have failed. Full article
(This article belongs to the Section Organic Chemistry)
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