Inverted energy gap law for the nonradiative decay in fluorescent floppy molecules: larger fluorescence quantum yields for smaller energy gaps. Issue 12 (26th April 2019) - Shi, Junqing
Abstract : The non-radiative decay of substituted dicyano-distyrylbenzenes in solution increase with the Franck–Condon energy, being opposite to the conventional energy gap law. Abstract : A data survey on experimental fluorescence quantum yields of (multi)substituted dicyano-distyrylbenzenes in fluid solution evidences that non-radiative decay increases with the Franck–Condon energy ( E FC ), being opposite to the conventional energy gap law. Quantum-chemistry indicates that this is controlled by access to the conical intersection (CI) following the Bell–Evans–Polanyi principle as a first-step approximation for this family of molecules; the variations in E FC among the different compounds are found to be decisive, while those of E CI are estimated to be weaker or even enhancing the effect. The current findings may have significant consequences for the design of molecules for organic solid state emitters.