间位取代卟啉及其锌卟啉的电子吸收光谱

摘要

取代的卟啉类衍生物在气敏传感器方面具有广泛的应用前景.本文采用了密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)研究了四种不同取代基的卟啉衍生物(meso位四硝基苯基/四氨基苯基卟啉(NO2PP,NH2PP)及其相应的锌金属卟啉衍生物(NO2ZnPP,NH2ZnPP))的紫外和近紫外光谱特征.利用两种不同的交换相关泛函(广义梯度近似泛函(PBE)和杂化密度泛函(B3LYP))优化了上述四种物质的结构,并应用TD-DFT计算了相应的电子激发能量和振动强度.结果表明,取代卟啉的吸收光谱与大量的电子跃迁有关；与B3LYP泛函预测的光谱相比,PBE泛函所得B带以及Q带的波长位置与实验值更为接近.另外,计算所得硝基取代基卟啉的B带相对于氨基取代基卟啉的B带发生了红移,这与实验现象也保持一致.由于卟啉衍生物的三重激发态在电子转移中有很重要的应用,因此在PBE/6-31G(d)水平上计算了四种物质的最低三重激发态能量,分别为1.426、1.469、1.608和1.581 eV.%Meso-substituted porphyrin derivatives have demonstrated great potential as sensing materials for toxic gas detection.In this paper,density functional theory (DFT) and its time-dependent DFT approach (TD-DFT) were employed to investigate the ultraviolet-visible (UV-Vis) or the near-ultravioletvisible (near-UV-Vis) absorption spectra of meso-tetra (o-nitrophenyl/o-aminophenyl) porphyrins (NO2PP,NH2PP) and their corresponding zinc derivatives,NO2ZnPP and NH2ZnPP.The geometry optimizations for these four molecules were obtained from two different exchange-correlation functionals,the generalizedgradient approximation functional PBE (Perdew-Burke-Ernzerhof) and the hybrid functional B3LYP (Becke,three-parameter,Lee-Yang-Parr).The excitation energies and oscillation strengths were obtained from TD-DFT calculations.Calculations show that the optical absorptions are associated with numerous electronic transitions.In addition,the PBE-predicted wavelengths of the B and Q bands are more consistent with experiment than those predicted by B3LYP.The B band of NO2-substituted derivative exhibits a bathochromic shift different from that of NH2-containing material,also consistent with experimental results.In addition,at the PBE/6-31G(d) level of theory,the calculated energies of the lowest triplet excited states of NO2PP,NH2PP,NO2ZnPP,and NH2ZnPP are 1.426,1.469,1.608,and 1.581 eV,respectively.