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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Excited States of Porphyrin Macrocycles
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Excited States of Porphyrin Macrocycles

机译：卟啉大环的激发态

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摘要

S1->S_n spectra of porphyrin,diprotonated porphyrin,and tetraoxaporphyrin dication have been measured in the energy range 2-3 eV above S1 at room temperature in solution by means of transient absorption spectroscopy exciting with femtosecond pulses.Highly excited pi pi* states not active in the conventional S_0-S_n spectrum have been observed.The experimental data are discussed on the basis of the time dependent density functional theory taking advantage of large scale calculations of configuration interaction between singly excited configurations(DF/SCI).The DF/SCI calculation on porphyrin has allowed to assign g states active in the S1->S_n spectrum.Applying the same calculation method to tetraoxaporphyrin dication the S_0->S_n spectrum is reproduced relatively to the Q and B(Soret)bands as well as to the weaker E_n bands at higher energy.According to our calculation the S1->S_n transient spectrum is related to states of g symmetry mainly arising from excitations between doubly degenerate pi and pi* orbitals such as 2e_g->4e_g.In the case of diprotonated porphyrin it is shown that the complex of the macrocycle with two trifluoroacetate anions plays a significant role for absorption.Charge transfer excitations from the anions to the macrocycle contribute to absorption above the Soret band,justifying the intensity enhancement of the S_0->S_n spectrum with respect to the other two macrocyclic systems.
机译：通过飞秒脉冲激发的瞬态吸收光谱法在室温下在溶液中S1上方2-3 eV的能量范围内测量了卟啉，双质子化卟啉和四氧杂卟啉的S1-> S_n光谱。观察到了在传统S_0-S_n光谱中具有活性的分子。基于时变密度泛函理论，利用大规模计算单激发构型（DF / SCI）之间构型相互作用的方法讨论了实验数据。通过对卟啉的计算可以分配S1-> S_n谱中活跃的g状态。将相同的计算方法应用于四氧杂卟啉指示，S_0-> S_n谱相对于Q和B（Soret）谱带以及相对弱的谱带得以再现根据我们的计算，S1-> S_n瞬态谱与g对称状态有关，这主要是由双简并之间的激发引起的pi和pi *轨道呈环状，例如2e_g-> 4e_g。在双质子化卟啉的情况下，表明大环与两个三氟乙酸根阴离子的络合物对吸收起着重要作用，电荷从阴离子到大环的电荷转移激发有助于Soret波段以上的光吸收，相对于其他两个大环系统，S_0-> S_n光谱的强度增强是合理的。

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