Achieving tunable dual-emissive and high-contrast mechanochromic materials by manipulating steric hindrance effects†
A series of unsymmetrical diphenylketone derivatives with tunable dual-emissive and high-contrast mechanochromic properties are reported. These compounds show dual-emissive bands in both solution and the solid state, by combining traditional fluorescence (ca. 426–459 nm) and intermolecular thermally activated delayed fluorescence (ca. 565–575 nm). Various photophysical studies and single crystal analyses are undertaken to demonstrate the dual-emissive mechanism and effect of bulky groups on regulating dual emissions. In addition, OPNa, OPAn and OPPy show white-light emission with the CIEx,y coordinates (0.32, 0.33), (0.33, 0.32) and (0.30, 0.34) in the solid state and high-contrast mechanochromism from blue and cold white to yellow emission. These studies present an ingenious design strategy for the development of high-performance multifunctional and single-component white-light-emitting materials.