9-(Diphenylphosphoryl)-10-(phenylethynyl)anthracene Derivatives: Synthesis and Implications for the Substituent and Solvent Effects on the Light-Emitting Properties

Herein, we report a series of 9-(diphenylphosphoryl)-10-(phenylethynyl)anthracenes (DPPPEAs) as novel fluorescent 9,10-disubstituted anthracene derivatives. The DPPPEAs were prepared by Sonogashira coupling of (10-bromoanthracen-9-yl)diphenylphosphine oxide with terminal arylacetylenes, and their structures were fully characterized. UV/Vis fluorescence spectroscopy and theoretical calculations were used to evaluate substituent effects on fluorescence properties of DPPPEAs. The nature of emissive excited state of DPPPEAs was found to vary greatly depending on the substituent, solvent, and temperature. Unsubstituted DPPPEA emitted intense fluorescence from locally excited (LE) state, whereas donor-acceptor (D-A) type DPPPEAs substituted with diphenylamino groups showed strong solvatofluorochromism derived from the charge-transfer (CT) state. Notably, carbazolyl derivatives exhibited fluorescence from LE hybridized with CT state. The disappearance of CT emission in rigid media suggests that solvent reorganization plays a crucial role in producing large Stokes shifts of D-A type derivatives. The DPPPEAs have also been found to function as annihilators in porphyrin-sensitized triplet–triplet annihilation processes.