Thermal and environmental effects on Oligothiophene low-energy singlet electronic excitations in dilute solution: a theoretical and experimental study
Thermal and environmental effects on Oligothiophene low-energy singlet electronic excitations in dilute solution: a theoretical and experimental study
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稀溶液中低聚噻吩低能单线态电子激发的热和环境影响：理论和实验研究
DOI：
10.1007/s00214-012-1177-z
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发表时间：
2012
影响因子：
1.7
通讯作者：
R. Po'
中科院分区：
文献类型：
--
作者：
M. Aschi;A. Amadei;Andrea Pellegrino;Nicola Perin;R. Po'
稀释二氯甲烷溶液的吸收光谱在300 K的四个Oligotiophenes (OT),即2、2:5,2”-Terthiophene 2 2: 5, 2”:5“,2”“-Quaterthiophene 4 4”“-Didodecyl-2 2”:5“,2”:5“,2”“-Quaterthiophene和5、5”“”-Dihexyl-2, 2: 5, 2”:5“,2”:5”“,2”:5“,2”“-sexithiophene,研究了实验和理论上通过使用分子动力学模拟的结合,含时密度泛函理论(TD-DFT)和摄动矩阵法计算。对理论结果的深入分析表明，环境（溶剂）和热效应显著地改变了Oligotiophenes的光物理性质，这主要是由于实际填充的不同构象在溶液中经历了广泛的S0-S1能隙和电子密度。特别是，所有研究的OT都显示出非常高的灵活性，从而产生非常高的采样构象库。S0-S1电子跃迁的计算线形和实验线形的比较清楚地表明，为了正确地模拟OT光谱特征，缺乏对整个系统的半经典构型空间的详尽采样，即溶质与溶剂的相互作用，可能导致一个不完整的画面，即使在有充分记录的重要方面，如激发态的可靠定义和量子振动效应的包含。
The absorption spectra in dilute dichloromethane solution at 300 K of four Oligotiophenes (OT), namely 2,2′:5′,2″-Terthiophene, 2,2′:5′,2″:5″,2″′-Quaterthiophene, 4,4″′-Didodecyl-2,2′:5′,2″:5″,2″′-quaterthiophene and 5,5′′′′′-Dihexyl-2,2′:5′,2′′:5′′,2′′′:5′′′,2′′′′:5′′′′,2′′′′′-sexithiophene, have been studied both experimentally and theoretically by using a combination of molecular dynamics simulations, time-dependent density functional theory (TD-DFT) and perturbed matrix method calculations. A deep analysis of the theoretical results, affected by a systematic although not dramatic underestimation of the absorption maxima due to the well-documented TD-DFT limitations, clearly indicates that both the environmental (solvent) and thermal effects significantly alter the Oligotiophenes photophysical properties mainly because of the wide repertoire of the S0–S1 energy gaps and electronic densities experienced in solution by the different conformers actually populated. In particular, all the investigated OT display a very high flexibility resulting in a very high repertoire of sampled conformations. The comparison of the calculated and experimental lineshape of the S0–S1 electronic transition has clearly indicated that for a correct modeling of OT spectral features, the lack of an exhaustive sampling of semiclassical configurational space of the overall system, i.e., solute in interaction with the solvent, might result in an incomplete picture even in the presence of well-documented important aspects such as reliable definition of excited electronic states and the inclusion of quantum vibronic effects.