We used first-principles calculations to investigate the photo-induced electron transfer (PIET) process of the hemicyanine-(TiO2)n complex ((TiO2)n-dye) for n=5, 9, 15. The geometries of the (TiO2)n-dye in the ground state were optimized using density functional theory (DFT) and their excited states were investigated using the time-dependent DFT (TDDFT) method. The excited energies, which were calculated using the long-range-corrected functionals, CAM-B3LYP andωB97X-D, were in good agreement with the experimentally observed values. The wave functions based on DFT were used to calculate the charge transfer integrals by the generalized Mul iken-Hush (GMH) approach. In addition, the photo-induced charge separation rate constant (kCS) and charge recombination rate constant (kCR) were calculated using Marcus theory. The calculated results showed that there were a cascade of electron transfer channels from the dye into the (TiO2)n cluster, which increases the kCS value. In contrast, the single channel of charge recombination decreases the kCR value, which is negligible compared with kCS, indicating that electron recombination is not favored.%采用第一性原理研究了半菁-二氧化钛团簇形成的配合物(hemicyanine-(TiO2)n)的光电子转移过程,这里n分别取5,9,15.配合物基态构型采用密度泛函理论方法进行优化,而激发态采用含时密度泛函理论进行计算.采用长程相关校正的密度泛函CAM-B3LYP和ωB97X-D计算的激发能与实验值吻合得很好.依据广义Mul iken-Hush (GMH)公式,基于密度泛函理论得到的波函数被用来计算电荷转移积分,进而可根据Marcus理论计算出电荷分离速率常数(kCS)和电荷回传速率常数(kCR).计算结果表明电子从染料到(TiO2)n团簇的传递有多条通道,这使得kCS具有更大值,相反,只具有单通道的电荷回传降低了kCR值,与kCS相比甚至可以忽略,这表明在所研究的体系中电荷回传是不利的.
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