Effect of terminal donors on the structures and photophysical properties of D–A-π-D small fluorophores

In order to investigate the effect of terminal donors on the structures and photophysical properties, four donor (D1)-acceptor (A)-π bridge-donor (D2) prototype fluorophores were synthesized and characterized. Single crystal analysis indicated that changing the types of terminal donors (D2) would give rise to different frontier molecular orbitals and molecular packing modes, leading to their different emission behaviors in solid states. In dilute solution, the four D–A–π-D compounds displayed different absorption and emission behaviors in dilute solution with solvatochromism properties. Assisted by the quantum chemical calculations and wave function analysis, the essence of optical properties of four compounds were explored. The results indicated that changing the types of terminal donors (D2) can affect the structures and photophysical properties of such donor (D1)-acceptor (A)-π bridge-donor (D2) prototype fluorophores, which provided guidance to design new fluorophores.