Omidyan Reza, Salehi Mohammad, Heidari Zahra
Department of Chemistry, University of Isfahan, 81746-73441, Isfahan, Iran.
Photochem Photobiol Sci. 2015 Dec;14(12):2261-9. doi: 10.1039/c5pp00266d.
The geometry, electronic structures and potential energy profiles of protonated furan and thiophene have been extensively investigated, using the RI-MP2 and RI-CC2 methods. According to RI-CC2 calculated results, the adiabatic S1((1)ππ*)-S0 transition energies of protonated furan and thiophene, have been predicted to be 4.41 eV and 3.70 eV respectively. Thus, protonation is accompanied by a large red shift effect on the first (1)ππ* transition of the title systems (ΔE > 1.5 eV). The significant spectral-movements, predicted based on the calculated results of this work, indicate an essential effect of protonation on the geometry, electronic structures and optical characters of the five membered heterocyclic systems. In addition, it has been found that excitation of protonated furan and thiophene, with sufficient excess energy above the band origin of S1((1)ππ*)-S0 transition, is accompanied by the S-C or O-C bond breaking. This mechanism is mostly governed by a dissociative (1)πσ* PE profile in both protonated systems.
使用RI-MP2和RI-CC2方法，对质子化呋喃和噻吩的几何结构、电子结构和势能分布进行了广泛研究。根据RI-CC2计算结果，质子化呋喃和噻吩的绝热S1((1)ππ*)-S0跃迁能量分别预测为4.41 eV和3.70 eV。因此，质子化伴随着对标题体系的第一(1)ππ跃迁的大红移效应(ΔE > 1.5 eV)。基于这项工作的计算结果预测的显著光谱移动，表明质子化对五元杂环体系的几何结构、电子结构和光学特性有重要影响。此外，还发现质子化呋喃和噻吩在高于S1((1)ππ)-S0跃迁带起源有足够多余能量时的激发，伴随着S-C或O-C键的断裂。在两个质子化体系中，这种机制主要由离解性的(1)πσ*势能分布决定。
