Pyrido[3,4-d]pyrimidine as an Acceptor of Thermally Activated Delayed Fluorescent Emitters: Time-dependent Density Functional Theory Study

Abstract

Pyrido[3,4-d]pyrimidine (PyPm) was designed as a new acceptor of thermally activated delayed fluorescent (TADF) emitters and the potential of the new acceptor moiety for TADF properties was investigated. Time-dependent density functional theory calculation was performed to estimate TADF characteristics by comparing five isomers of PyPm-based TADF emitters. Geometries of the emitters were affected by the presence of hydrogen bonding depending on the substitution position of the phenyl linker in the donor-phenyl linker-acceptor type backbone structure, which also influenced the molecular orbital distributions. The nature of the triplet excited state was also dependent on the substitution position of the phenyl linker and donor moiety in the molecular structure, and the substitution at 5 position of the PyPm provided small singlet-triplet energy gap and hybridized local and charge transfer triplet excited state for efficient reverse intersystem crossing. From the computational calculation results, it can be expected that PyPm would effectively work as an acceptor of TADF emitters.