In recent years, organic donor-acceptor complexes have attracted much attention, leading to the development of new organic switchable, binary electronic materials with high data-storage capacity. Following addition of a solution of maleic anhydride to a solution of imidazo[1,2-a]pyridine(s), a cascade reaction ensues, resulting in the formation of cross-conjugated mesomeric betaines (CCMB), wherein positive and negative charges are restricted exclusively to different parts of the molecule. Physico-chemical properties of the compounds revealed the existence of intramolecular charge-transfer phenomena which could stimulate their interest as potential luminescent materials.

Organic Donor Acceptor (DA) complexes have emerged in recent years as materials of choice for the organic binary electronics. The reactivity de-scriptors derived from the conceptual DFT reveal imidazo[1,2-a]pyridines as potential donors. In view of this, four imidazo[1,2-a]pyridines reacted with tetracyanoethylene (TCNE) in 1:2 molar ratio to afford four new DA complexes. The spectral studies, namely IR, 1H, 13C, DEPT 135, 2D HMQC NMR, and HRMS were used to establish the structures. The UV-vis. spectroscopy reveals intramolecular charge transfer. All the four compounds fluoresce giving excitation emission fluorescence spectra with a red shift ranging from 64 to 151 nm and quantum yields from 0.004 to 16.35. Unexpectedly, nitro group in one of the products does not act as quencher; instead, it enhances the quantum yield to make it highest in this series. The products exhibit electrical conductivity which increases with temperature. The SEM and TEM images reveal distinct and homogenous surface morphology with holes which facilitate flow of electrons as manifested by electrical conductivity. The powder XRD and SAED results establish the polycrystalline nature of the products. The theoretical studies indicate an alternate donor acceptor stacking pattern.

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