Investigation of Phosphine Ligand Effect on Tunable Optical Property of Novel Coumarin‐Triphenyliminophosphorane Fluorophores

We report the synthesis and investigation of the photophysical properties of a series of coumarin‐triphenyliminophosphorane (TPIPP) derivatives containing an electron‐withdrawing trifluoromethyl ketone (TFMK) group at the C‐3 position. The concept of nonhydrolytic Staudinger reaction (NSR) was employed to prepare stable coumarin‐TPIPP compounds, and introduction of para‐substituted electron‐donating or electron‐withdrawing groups on the PPh 3 ligands significantly influenced the optical behavior of the coumarin‐TPIPP derivatives. Compounds with more electron‐donating substituents exhibited red‐shifted absorption and emission maxima, as well as enhanced two‐photon absorption (2PA) properties under near‐infrared excitation. The substituent effect on the ground and excited‐state dipole moments was also investigated using the solvatochromic shift method, revealing a decrease in the dipole moment change as the number of para‐substituents increased. The polarized P═N bond feature, along with the favorable intramolecular charge transfer process, contributes to 2PA behavior of the coumarin‐TPIPP compounds with tunable fluorescence profiles, providing a promising strategy for the design of novel luminescent materials.