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The Ground and Excited States of Polyenyl Radicals C 2 n −1 H 2 n +1 ( n =2–13): A Valence Bond Study
Author(s) -
Luo Yan,
Song Lingchun,
Wu Wei,
Danovich David,
Shaik Sason
Publication year - 2004
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200300935
Subject(s) - excited state , chemistry , unpaired electron , radical , ground state , valence (chemistry) , atomic physics , covalent bond , valence bond theory , excitation , valence electron , molecular orbital , electron , molecule , physics , quantum mechanics , organic chemistry
The semiempirical valence bond (VB) method, VBDFT(s), is applied to the ground states and the covalent excited states of polyenyl radicals C 2 n −1 H 2 n +1 ( n =2–13). The method uses a single scalable parameter with a value that carries over from the study of the covalent excited states of polyenes (W. Wu, D. Danovich, A. Shurki, S. Shaik, J. Phys. Chem. A , 2000 , 104 , 8744). Whenever comparison is possible, the VB excitation energies are found to be in good accord with sophisticated molecular orbital (MO)‐based methods like CASPT2. The symmetry‐adapted Rumer structures are used to discuss the state‐symmetry and VB constitution of the ground and excited states, and the expansion to VB determinants is used to gain insight on spin density patterns. The theory helps to understand in a coherent and lucid manner the properties of polyenyl radicals, such as the makeup of the various states, their geometries and energies, and the distribution of the unpaired electrons (the neutral solitons).