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DFT Study on Structural Distortion and Vibronic Coupling of Vanadyl Porphyrin Anion and Cation
Hui-ling Gao,Fang Chen,Guo-hua Yao,Dong-ming Chen*
Author NameAffiliationE-mail
Hui-ling Gao Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Fang Chen Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Guo-hua Yao Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Dong-ming Chen* Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China dmchen@ustc.edu.cn 
Abstract:
The geometries of one-electron reduced/oxidized species ([TOP]-/[VOP]+) of vanadyl por-phyrin (VOP) have been calculated with PBE1PBE method. The results show that for both [VOP]- and [VOP]+ the ground states are triplet, in which one of the two unpaired electron occupies the dxy orbital of the V atom while the other occupies the π-orbital of porphyrin ring. Thus both [VOP]- and [VOP]+ can be considered as π-radicals. The ground state of neutral VOP molecule is doublet with the unpaired electron occupying dxy orbital of V atom. In contract to the C4v symmetry of neutral VOP molecule, [VOP]- anion has a "rectangular" distorted C2v structure due to Jahn-Teller effect. The linear vibronic coupling constants for the Jahn-Teller active modes of [TOP]- were evaluated and the node patterns of frontier KS orbitals are used to explain the reason why the distortion occurs along specific modes. The ground state [VOP]+ has a porphyrin ring with pronounced bond length alternation due to pseudo-Jahn-Teller effect, causing its symmetry declined from C4v to C4. The bond length alternation is well explained with the node patterns of re-constructed frontier KS orbitals.
Key words:  Vanadyl porphyrin, Jahn-Teller effect, Vibronic coupling
FundProject:
钒氧卟啉正负离子的结构畸变与电子-振动耦合的DFT研究
高慧玲,陈方,姚国华,陈东明*
摘要:
用PBE1PBE方法研究了钒氧卟啉一价阴离子([VOP]-)、一价阳离子([VOP]+)的单态和三重态结构. 结果表明[VOP]-和[VOP]+的最稳定电子态均为三重态,其未配对电子一个占据钒的dxy轨道,另一个占据卟啉环的π轨道,因此两者均为π-自由基. 中性分子(VOP)的双重态最稳定,其未配对电子占据钒的dxy轨道. 双重态VOP具有较高的C4v对称性,而三重态[VOP]- 离子由于发生姜-泰勒效应对称性降低为C2v. 计算了[VOP]-姜-泰勒活性振动模式的电子-振动耦合常数,并用前线KS轨道的节面分布解释了姜-泰勒畸变沿特定简正模式发生的原因. 三重态[VOP]+ 阳离子的卟啉环发生键长交替变化,构型畸变起源于电子态近简并引起的赝姜-泰勒效应,导致其对称性从C4v降低为C4,其结构变化可以用重组的前线KS轨道的节面分布解释.
关键词:  钒氧卟啉,π-自由基,姜-泰勒效应,电子-振动耦合
DOI:10.1063/1674-0068/26/05/504-511
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