Excited states of free base phthalocyanine studied by the SAC-CI method
Excited states of free base phthalocyanine studied by the SAC-CI method
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DOI：
10.1021/jp9617635
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发表时间：
1997-01-23
影响因子：
2.9
通讯作者：
Nakatsuji, H
中科院分区：
文献类型：
--
作者：
Toyota, K;Hasegawa, J;Nakatsuji, H
使用SAC（对称适应簇）/SAC-CI 方法计算游离碱酞菁（FBPc）的基态和激发态。这是首次对 FBPc 激发态进行准确的从头算研究。计算出的电子能谱与能量和强度方面的实验结果相当吻合。讨论了分子结构、激发能和光谱强度之间的关系，并将目前的结果与之前研究的游离碱卟啉（FBP）和游离碱四氮杂卟啉（FBTAP）的结果进行了比较。骨骼变化的两个重要影响得到澄清；中四氮杂取代和四苯并取代导致HOMO和下一个HOMO能级之间的大分裂，并导致Q带的两个主要构型的准简并性的崩溃，由于个体对跃迁偶极矩的贡献的不完全抵消而导致强烈的可见光吸收。这就解释了为什么个人电脑作为颜料如此有用。此外，还提出了 B（Soret）频段的新分配。广泛的实验B带至少由四个状态组成。 B带的主峰是由于低于所谓“四轨道”的轨道的跃迁，而由“四轨道”产生的跃迁构成了能带较低能量侧的肩部。
The SAC (symmetry adapted cluster)/SAC-CI method was used to calculate the ground and excited states of free base phthalocyanine (FBPc). This is the first accurate ab initio study of the excited states of FBPc. The calculated electronic spectrum agrees reasonably well with experimental results with regard to both energy and intensity. The relationships among the molecular structure, excitation energy, and spectral intensity are discussed, and the present results are compared with those for free base porphine (FBP) and free base tetrazaporphine (FBTAP) studied previously. Two important effects of skeletal changes are clarified; mesotetraaza substitution and tetrabenzo substitution cause a large splitting between the HOMO and next HOMO levels and lead to a breakdown of the quasi-degeneracy of the two main configurations of the Q band, resulting in strong visible absorption due to the incomplete cancellation of the individual contributions to the transition dipole moment. This explains why Pc's are so useful as pigments. Further, a new assignment of the B (Soret) band is proposed. The broad experimental B band is composed of at least four states. The main peak of the B band is due to transitions from the orbital lower than the so-called ''four orbitals'', and the transitions arising from the ''four orbitals'' constitute the shoulder in the lower energy side of the band.