Geometry deformation and mesomeric effect at the minimal-energy conical intersections and their relationship to the photoreactivity of indolylfulgides: A TD-DFT study

Minimum energy conical intersection (MECI) is the low-lying point on the CI hyperseam that facilitates ultrafast radiationless transition in photochromes. Time dependent density functional theory calculations using Maeda’s updated branching plane method were employed in the study of indolylfulgides’ structure at the MECI. Four criteria were used to effectively characterize the influence of the MECI structure on the photoreactivity of indolylfulgides; three of these criteria (molecular orbital, bond lengths and the height of C6 trigonal pyramid) were paramount to identifying one novel MECI structure and confirming 2 others previously reported.