Modulating p−π Conjugation with Hybridized Local and Charge-Transfer Excited-State Manifolds: Toward Bimodal Photocatalysts for Efficient Energy and Electron Transfer Catalysis

Precise control of excited-state electronic communication and spin dynamics is critical for advancing optoelectronic properties and the photocatalytic function of purely organic materials. Herein, we present a molecular design strategy for chromophores by tuning p−π conjugation through engineering locally excited (LE), charge-transfer (CT), or hybridized local and charge-transfer (HLCT) excited-state manifolds, depending on the nature and number of donors. Systematic modulation of π-arylamines and para -substitution with saturated cyclic amine on a benzonitrile (BN) core yields asymmetric donor–acceptor systems ( PC1–PC5 ) with tailored photophysical properties, excited-state character, and redox behavior. The strong electronic effects and twisted chair conformations of morpholine-integrated cyanobenzene dyes suppress aggregation-induced quenching, enabling tunable solid-state emission from vibrant blue to orange-red with distinct excited-state fluorescence or phosphorescence. Among the series, 2DPA2FBN(Mor) stands out for its high photoluminescence quantum yield and good photocatalytic efficiency, enabling both energy- and electron-transfer (EnT/ET) transformations under visible light in organic solvents, aqueous media, and bulk liquid monomers. Comprehensive spectroscopic, electrochemical, and computational studies reveal that the long-lived HLCT state with effective p−π conjugation broadens the excited-state redox window (−2.19/+1.86), enabling dual photoredox reactivity and triplet–triplet energy transfer. This structure–property–function relationship provides a general framework for designing cost-effective multifunctional bimodal photocatalysts with a wide bandgap ( E g > 3.0 eV).