Effects of introducing nitrogen atoms into oligoacene skeleton on vibronic coupling and singlet fission dynamics

[Display omitted] •Introduction of N atoms into oligoacene skeletons is theoretically predicted to enhance VC involved in SF.•Substitution position dependence of VC is clarified from the theoretical analysis.•Introduction of N atoms into hydrocarbon also results in large S1 – TT gap.•Tuning multiple factors synergistically is indispensable for efficient SF molecular/materials design. We theoretically investigated the effects of introducing N atoms into the oligoacene backbone on singlet fission (SF) dynamics via changes in the vibronic coupling (VC). Quantum chemical calculations have revealed that the tetraaza-pentacenes and tetraaza-hexacenes studied here tend to exhibit larger VC than their oligoacene counterparts. The SF transition rates of these tetraaza-oligoacenes were enhanced mainly due to both the decrease in the energy difference between the initial and final states and the increase in VC. From these theoretical results, we discussed the strategy of heteroatom substitution to achieve efficient SF molecules from both energetic and VC viewpoints.