Pechenaya V I, Danilov V I, Slyusarchuk O N, Alderfer J L
Institute of Theoretical Physics of the National Academy Sciences of Ukraine, Kiev.
Photochem Photobiol. 1995 May;61(5):435-41. doi: 10.1111/j.1751-1097.1995.tb02341.x.
Theoretical modeling of initial steps of the photodimerization mechanism of uracil, 5-methyl-and 5-halogen derivatives was performed. The interaction energy of bases in stacked dimers in the ground and lowest excited states was calculated as a function of the distance between the base planes and of the rotation angles within the perturbation theory for the extended Hückel treatment. The existence of excimer and exciplex region on the potential surface of the excited state was revealed. The excimer (exciplex) geometry has the planes nonparallel with more close contact of the C5-C6 bonds as compared to the ground state of dimers. The results provide new information useful for understanding the photodimerization mechanism of bases and testifies that the singlet excimer state can be a precursor of the photodimerization reaction.
对尿嘧啶、5-甲基尿嘧啶和5-卤代尿嘧啶衍生物光二聚化机理的初始步骤进行了理论建模。在扩展休克尔处理的微扰理论中，计算了基态和最低激发态下堆积二聚体中碱基的相互作用能，作为碱基平面间距离和旋转角度的函数。揭示了激发态势能面上准分子和激基复合物区域的存在。与二聚体的基态相比，准分子（激基复合物）几何结构中平面不平行，C5-C6键的接触更紧密。这些结果为理解碱基的光二聚化机理提供了有用的新信息，并证明单重态准分子态可能是光二聚化反应的前体。
