Design, Synthesis and Selective Functionalization of a Rigid, Truxene Derived Pure Blue-Emitting Chromophore

Abstract

A novel, rigid, solution processable, blue-emitting chromophore based on an extended core of truxene (ExT) was designed and synthesized. The core, ExT based on a fused cyclic trimer of indenofluorene, was found to be planar in nature and a potential precursor for blue emission. This could be selectively brominated under mild conditions to generate a tribromo derivative which underwent ready Suzuki coupling to generate a trisubstituted pyrene derivative, ExT-P. This coupling alters the kinetics of the excited state considerably as evident from transient absorption spectroscopy, showing faster singlet state decay and less triplet state formation in the case of the pyrene coupled ExT-P (∼1.6 ns) compared to ExT (∼17 ns). The ExT-P shows emission maxima at 441 nm and 442 nm in THF solution and film, respectively, with high PLQY value of 0.97. The negligible bathochromic shift in the solid-state emission and narrow FWHM suggests practically no aggregation and pure blue emission in the target molecule due to bulky and rigid core.