7,7-bis(N, N-diethylethylenediamino)-8,8-dicyanoquinodimethane: Effect of Ethyl Moiety on the Photophysical Property besides Thermal Stability.

Tetracyanoquinodimethane (TCNQ) on reaction with primary/secondary amines sequels in mono/di-substituted TCNQ adducts known as diaminodicyanoquinodimethanes (DADQ's) possessing astounding optical or non-linear optical characteristics. Crucially, the subtle choice of amine contributes to the outcome of molecular material aspects. Herein, we present a comprehensive investigation of 7,7-bis(N,N-diethylethylenediamino)-8,8-dicyanoquinodimethane (BDEDDQ); manifesting the impact of ethyl group (existing on the di-substituted nitrogen of N,N-diethylethylenediamine (DEED)); on the crystal structure, optical property and thermal stability. Crystallography study revealed supramolecular self-assemblies among molecular dipoles emanating fluorescence enhancement in the solid state compared to solutions. Quantum yields were primarily ~0.2 to 0.4% in solutions and ~56% in the solid. Stokes shift was noticed to be more in solutions (~90 nm) than solid (~67 nm), suggesting excess vibrational relaxations in solutions. Differential scanning calorimetry revealed ~182 °C as the melting temperature. The heat capacity of solid was found to be 5.03 mJs