School of Natural Sciences, University of California Merced, 5200 N. Lake Road, Merced, California 95343, USA.
Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ, United Kingdom.
J Chem Phys. 2017 Mar 28;146(12):124504. doi: 10.1063/1.4979196.
The solvatochromic shift, as well as the change in colour of the simple organic dye nile red, is studied in two polar and two non-polar solvents in the context of large-scale time-dependent density-functional theory (TDDFT) calculations treating large parts of the solvent environment from first principles. We show that an explicit solvent representation is vital to resolve absorption peak shifts between nile red in n-hexane and toluene, as well as acetone and ethanol. The origin of the failure of implicit solvent models for these solvents is identified as being due to the strong solute-solvent interactions in form of π-stacking and hydrogen bonding in the case of toluene and ethanol. We furthermore demonstrate that the failures of the computationally inexpensive Perdew-Burke-Ernzerhof (PBE) functional in describing some features of the excited state potential energy surface of the S state of nile red can be corrected for in a straightforward fashion, relying only on a small number of calculations making use of more sophisticated range-separated hybrid functionals. The resulting solvatochromic shifts and predicted colours are in excellent agreement with experiment, showing the computational approach outlined in this work to yield very robust predictions of optical properties of dyes in solution.
溶剂化变色以及简单有机染料尼罗红的颜色变化，在大规模含时密度泛函理论（TDDFT）计算的背景下，在两个极性和两个非极性溶剂中进行了研究，这些计算从第一性原理出发处理了大部分溶剂环境。我们表明，对于尼罗红在正己烷和甲苯以及丙酮和乙醇中的吸收峰位移，显式溶剂表示至关重要。对于这些溶剂，隐式溶剂模型失败的原因被确定为是由于在甲苯和乙醇中存在强烈的溶质-溶剂相互作用，表现为π堆积和氢键。我们进一步证明，对于描述尼罗红 S 态激发态势能面某些特征的计算成本低廉的 Perdew-Burke-Ernzerhof（PBE）函数的失败，可以通过仅依赖于少数利用更复杂的分段混合泛函进行的计算来进行纠正。所得的溶剂化位移和预测的颜色与实验非常吻合，表明本文中概述的计算方法能够对溶液中染料的光学性质进行非常可靠的预测。
