Zwitterionic diaminodicyanoquinodimethanes with enhanced blue–green emission in the solid state

Diaminodicyanoquinodimethane molecules which show strong solid state emission in the blue–green region are developed. The new materials are structurally characterized; extended supramolecular assemblies mediated by H-bond interactions are observed in the crystal lattice. Spectroscopic studies including life-time and fluorescence quantum yield measurements in the solution and solid states are carried out. Emission in the solid state is ∼400 times stronger than that in solution; this can be attributed to the inhibition of the excited state geometry relaxation to a non-radiative state, in the solid. Impact of the molecular structure in the crystals on the solid state light emission is discussed. Semiempirical computational studies provide useful insight into the various structural and spectroscopic features of the new materials. The present observations serve as a pointer to further design strategies for realizing novel blue photoluminescent molecular materials based on the diaminodicyanoquinodimethane framework.

► Zwitterionic diaminodicyanoquinodimethanes showing strong blue-green solid state emission. ► Crystallographic and spectroscopic characterization of the new materials. ► Emission in the solid state ∼400 times stronger than in solution. ► Semiempirical computations to understand the structural and spectroscopic features. ► Tuning the solid state photoluminescence of diaminodicyanoquinodimethanes.