Effect of Topology on the Singlet–Triplet Energy Difference and their Natures: A Density Functional Theory Study of Carbazolyl‐Phthalonitrile Derivatives

[摘要] The molecular topology effect of carbazolyl‐phthalonitrile (CzPN) derivatives on their electronic structures were theoretically explored at the density functional theory level using a gap‐tuned range‐separated functional, ωB97X, with 6‐31G(d) basis sets. In the case of single carbazolyl (Cz) group onto the phthalonitrile (PN), the substitution at chemically inequivalent positions apparently does not significantly impact on the lowest unoccupied molecular orbital (LUMO); however, it results in a significant difference in the natures and energies of the highest occupied molecular orbitals (HOMO). As a result, it gives rise to a marked difference in their singlet excited‐state energies, although the variation in the T1‐state energies appears to be relatively limited. Additional introductions of Cz group, however, are found to suppress such variations, because the inductive electron‐withdrawing character of Cz group becomes more important than its mesomeric effect. Nevertheless, the difference in natures of the excited states, which is important to enhance the spin‐orbit coupling between them, can be induced by tweaking the molecular structures.

[学科分类] 化学（综合）

[关键词] Thermally activated delayed fluorescence;Singlet‐triplet energy difference;Natures of the excited states;Density functional theory study;Structure‐property relationship