Structural control of the excited-state dynamics of bis(dipyrrinato)zinc complexes: Self-assembling chromophores for light-harvesting architectures

The replacement of the phenyl rings at the 5,5′-positions of a bis(dipyrrinato)zinc complex with mesityl groups transforms the molecule from a very weak emitter that deactivates rapidly after photoexcitation (Φf = 0.006; τ ≈ 90 ps) to a highly fluorescent chromophore with a long-lived singlet excited state (Φf = 0.36; τ ≈ 3 ns). The results demonstrate that steric constraints on aryl-ring internal rotation dramatically alter the excited-state properties of 5,5′-substituted bis(dipyrrinato)metalcomplexes. The insights establish the foundation for tuning the photophysical properties of these chromophores for use in diverse photochemical applications. Copyright © 2004 American Chemical Society.