Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, USA.
J Phys Chem A. 2009 Nov 12;113(45):12396-403. doi: 10.1021/jp901601u.
A recently developed combined quantum mechanics/molecular mechanics (QM/MM) approach has been applied to the calculation of solvatochromic shifts of the excited states of the pyrimidine nucleobases uracil and cytosine in aqueous solution. In this procedure the quantum mechanical solute is described using a multireference configuration interaction method while molecular dynamics simulations are used to obtain the structure of the solvent around the solute. The fragment molecular orbital multiconfiguration self-consistent field (FMO-MCSCF) method of Fedorov and Kitaura is also used and compared with the QM/MM results. The two methods give similar results. The solvatochromic shifts in uracil are found to be +0.41 (+0.44) eV for the S(1) excited state and -0.05 (-0.19) eV for the S(2) state at the QM/MM (FMO-MCSCF) level. Solvatochromic shifts in cytosine are calculated to be +0.25 (+0.19), +0.56 (+0.62), and +0.83 (+0.83) eV for the S(1), S(2), and S(3) states, respectively, at the QM/MM (FMO-MCSCF) level.
最近开发的一种组合量子力学/分子力学（QM/MM）方法已应用于嘧啶碱基尿嘧啶和胞嘧啶在水溶液中激发态溶剂化位移的计算。在该程序中，量子力学溶质使用多参考组态相互作用方法进行描述，而分子动力学模拟用于获得溶质周围溶剂的结构。还使用了 Fedorov 和 Kitaura 的片段分子轨道多组态自洽场（FMO-MCSCF）方法，并将其与 QM/MM 结果进行了比较。这两种方法给出了相似的结果。在 QM/MM（FMO-MCSCF）水平下，计算出尿嘧啶的 S(1)激发态溶剂化位移为+0.41（+0.44）eV，S(2)态为-0.05（-0.19）eV。在 QM/MM（FMO-MCSCF）水平下，计算出胞嘧啶的 S(1)、S(2)和 S(3)态的溶剂化位移分别为+0.25（+0.19）、+0.56（+0.62）和+0.83（+0.83）eV。
