叶绿素a激发态电子结构的量子化学计算  

Theoretical Comparison for the Excited States of Chlorophyll-a by Quantum-chemical Calculations

作　　者：杨家瑜[1] 尹世伟[1] 杨永梅[1] 李兰兰[1] 

机构地区：[1]陕西师范大学化学与材料科学学院,大分子科学陕西省重点实验室,西安710062

出　　处：《高等学校化学学报》2011年第5期1129-1137,共9页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:20833004)资助

摘　　要：采用密度泛函理论DFT(B3LYP/6-31G)对氢取代后叶绿素的几何构型进行优化,并用不同的量子化学方法如ZINDO-CIS,TD-DFT和SAC-CI计算激发态能量,考察叶绿素的侧链和单线态根数目对激发态能量的影响,并计算Qy态跃迁偶极矩与y轴的夹角.结果表明,CAM-B3LYP泛函形式是计算叶绿素a前4个激发态特征的最佳方法,与高精度方法SAC-CI的结果是一致的.Time-dependent density functional theory（TD-DFT） is extensively applied to calculate the excited state of pi-conjugated molecules.But the conventional functional will underestimate the energies of excited states with charge transfer character.A new density functional,Coulomb-attenuated hybrid excharge-correlation functional（CAM-B3LYP） has recently been developed to overcome these limitations.In this paper,the four lowest excited states of chlorophyll-a were calculated by accurate SAC-CI（symmetry adapted cluster coupled configuration interaction）,ZINDO（Zerner＇s intermediate neglect of differential overlap） and various time-dependant DFT methods.The influences of substituents and Nstate on the excited states of chlorophyll-a were discussed.The orientation of three-dimensional transition dipole moment of the Qy band was assigned by different methods.Among different DFT methods,CAM-B3LYP is the best method to describe the four lowest excited states of chlorophyll-a.The CAM-B3LYP results are in excellent agreement with accurate SAC-CI results.

关 键 词：含时密度泛函 Qy跃迁偶极距方向 叶绿素A 

分 类 号：O641.3[理学—物理化学]