Reaction path of the excited-state double proton transfer (ESDPT) in the homodimer of 7-azaindole (7AI₂ homodimer) and heterodimer of 6H-indolo[2,3-b]quinoline and 7-azaindole (6HIQ-7AI heterodimer) is computationally studied by means of intrinsic reaction coordinate (IRC) calculations. The IRC path determined at the TDDFT level predicts the concerted-asynchronous mechanism for the ESDPT in 6HIQ-7AI as well as in 7AI₂, where the N–H$\cdots$N hydrogen bonds exhibit asymmetric structures along the reaction path with a single energy barrier. The IRC calculations at the CIS level, however, exhibits a local minimum for single-proton-transferred intermediate, suggesting the stepwise mechanism. Single-point energy calculations at the RI-CC2 level reproduce the TDDFT results, but do not the CIS results. On the basis of potential-energy profiles calculated against intermolecular distance, the discrepancy between the TDDFT and CIS methods is likely attributed to the underestimation of intermolecular interaction energy in the latter method due to the lack of dynamical electron correlation.

7-氮杂吲哚的同二聚体（7AI ₂同二聚体）和6H-吲哚并[2,3-b]喹啉和7-氮杂吲哚的异二聚体（6HIQ-7AI异二聚体）的激发态双质子转移（ESDPT）的反应路径为通过内在反应坐标（IRC）计算进行计算研究。在TDDFT级别确定的IRC路径可预测6HIQ-7AI和7AI ₂中ESDPT的协调异步机制，其中N–H$\cdots$N个氢键沿反应路径具有不对称结构，具有单个能垒。但是，在CIS级别上的IRC计算显示了单质子转移中间体的局部最小值，表明了逐步机理。RI-CC2级别的单点能量计算会重现TDDFT结果，但不会重现CIS结果。根据针对分子间距离计算的势能分布图，由于缺乏动态电子相关性，TDDFT和CIS方法之间的差异很可能归因于后一种方法中分子间相互作用能的低估。