A molecular orbital study on a tetra-aza macrocycle containing 2,2′-bipyridines and its lithium complex
A molecular orbital study on a tetra-aza macrocycle containing 2,2′-bipyridines and its lithium complex
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2,2-联吡啶四氮杂大环及其锂配合物的分子轨道研究
DOI：
10.1039/a808388f
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
S. Tsuchiya
中科院分区：
文献类型：
--
作者：
K. Takano;A. Furuhama;S. Ogawa;S. Tsuchiya
在从头算RHF/3- 21 G优化几何条件下，用CNDO/SCI方法计算了含四个吡啶环的二氰基双四氮杂大环及其锂配合物的两种构型异构体的单重态跃迁能和振子强度.结果与紫外-可见吸收光谱结果一致。发现反式异构体络合后观察到的剧烈光谱变化是由于联吡啶部分的显著构象变化和由此产生的前线π轨道的能量分离。三重态和单重激发态之间的接近表明，系间交叉可能发生在无锂大环的反式形式。这是大环的反式异构体与其锂络合物之间荧光强度差异较大的可能解释之一。
Singlet transition energies and oscillator strengths of two configurational isomers of a dicyano dibutyl tetra-aza macrocycle containing four pyridine rings and their lithium complexes were calculated using the CNDO/S CI method at ab initio RHF/3-21G optimized geometries. The results were in good agreement with those derived from the UV-Visible absorption spectra. The drastic spectral changes observed upon complexation in the trans-isomer were found to be due to the significant conformational change in the bipyridine moiety and the resulting energy separation of the frontier π orbitals. The close proximity between the triplet states and the singlet excited state suggested that the intersystem crossing might occur in the trans form of the lithium free macrocycle. This is one of the possible explanations of the large discrepancy in fluorescence intensities between the trans-isomer of the macrocycle and its lithium complex.