Minaev Boris
State University of Technology, Cherkassy 18006, Ukraine.
Spectrochim Acta A Mol Biomol Spectrosc. 2004 Nov;60(13):3213-24. doi: 10.1016/j.saa.2004.03.005.
The radiative lifetime of phosphorescence of free-base porphin (H2P) molecule and its complexes with noble-gas atoms are calculated by time-dependent density functions theory (TD DFT) with quadratic response functions for account of spin-orbit coupling and electric dipole activity. The complexes with Ne, Ar, Kr, and Xe are used to simulate the external heavy atom (EHA) effect on phosphorescence of the H2P molecule in the corresponding noble gas matrices. The B3LYP functional and small basis set (3-21G) are used throughout the study and comparison of all complexes but other basis sets are also utilized to support the chosen approach. A slow radiative rate constant of free-base porphin phosphorescence (about 10(-3) s(-1)) is obtained with all basis sets being in the order of magnitude agreement with experimental estimations. A strong enhancement of the H2P phosphorescence rate (by 360 times) is calculated for Xe complex; while for Ne, Ar, and Kr complexes, the enhancement is equal to 1.1, 1.3, and 10.3 times, respectively. In these complexes, the noble gas atom is disposed at 3.6 A above the center of the porphin ring. In spite of shortcomings of the chosen simple model, the TD DFT calculations explain the most important features of the EHA effect on phosphorescence of free-base porphin. Calculations of the hyperfine coupling tensors for all magnetic nuclei in the lowest triplet state of H2P molecule and its complexes with noble-gas atoms indicate an appreciable penetration of the spin density to the EHA region. This can be connected with the enhancement of spin-orbit coupling in the H2P molecule.
采用含时密度泛函理论（TD DFT）结合二次响应函数计算了游离碱卟啉（H2P）分子及其与稀有气体原子形成的配合物的磷光辐射寿命，以考虑自旋 - 轨道耦合和电偶极活性。利用与Ne、Ar、Kr和Xe形成的配合物来模拟外部重原子（EHA）对相应稀有气体基质中H2P分子磷光的影响。在整个研究和所有配合物的比较中均使用了B3LYP泛函和小基组（3 - 21G），但也采用了其他基组来支持所选方法。使用所有基组都得到了游离碱卟啉磷光的缓慢辐射速率常数（约10^(-3) s^(-1)），其数量级与实验估计值一致。计算得出Xe配合物使H2P磷光速率强烈增强（增强360倍）；而对于Ne、Ar和Kr配合物，增强倍数分别为1.1、1.3和10.3倍。在这些配合物中，稀有气体原子位于卟啉环中心上方3.6 Å处。尽管所选的简单模型存在缺点，但TD DFT计算解释了EHA对游离碱卟啉磷光影响的最重要特征。对H2P分子及其与稀有气体原子形成的配合物的最低三重态中所有磁性核的超精细耦合张量的计算表明，自旋密度明显渗透到EHA区域。这可能与H2P分子中自旋 - 轨道耦合的增强有关。
