期刊
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
卷 155, 期 -, 页码 95-102出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.saa.2015.11.002
关键词
Circular dichroism; Density functional theory; Substituent effect; Nitro group; Absolute configuration determination; Charge transfer; CAM-B3LYP
类别
资金
- [TAMOP-4.2.2.B-10/1-2010-0009]
B3LYP is one of the most widely used functional for the prediction of electronic circular dichroism spectra, however if the studied molecule contains aromatic nitro group computations may fail to produce reliable results. A test set of molecules of known stereochemistry were synthesized to study this phenomenon in detail. Spectra were computed by B3LYP and CAM-B3LYP functionals with 6-311 ++G(2d,2p) basis set. It was found that the range separated CAM-B3LYP gives better predictions than B3LYP for all test molecules. Fragment population analysis revealed that the nitro groups form highly localized molecule orbitals but the exact composition depends on the functional. CAM-B3LYP allows sufficient spatial overlap between the nitro group and distant parts of the molecule, which is necessary for the accurate description of excited states especially for charge transfer states. This phenomenon and the synthesized test molecules can be used to benchmark theoretical methods as well as to help the development of new functionals intended for spectroscopical studies. (C) 2015 Elsevier B.V. All rights reserved.
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