Preparation of phosphine oxides with anthrylphenyl, pyrenylphenyl, anthrylethynyl, and pyrenylethynyl groups: luminescence properties and conformational polymorphs

Abstract

Precise control of crystal polymorphism provides a powerful strategy to tune luminescence, yet remains a major challenge in molecular material design. We show that introducing ethynylene linkers into phosphine oxide derivatives bearing anthryl and pyrenyl groups enables polymorphism through diverse intermolecular interactions, whereas phenylene-bridged analogues crystallize in a single form. Single-crystal X-ray diffraction confirmed distinct packing arrangements, and optical studies revealed extended π-conjugation with bathochromic shifts, as well as packing-dependent modulation of excited-state vibrational levels. These results establish a direct structure–property relationship between polymorphism and emission, offering a versatile molecular design principle for next-generation optoelectronic and photonic materials.