A novel chlorocadmate hybrid cocrystal delivering intermolecular charge transfer enhanced nonlinear optical properties and optical limiting

Employing the donor-acceptor configuration of cocrystals, the intermolecular charge transfer enhanced third order nonlinear optical properties and the optical limiting behaviour of a novel chlorocadmate cocrystal {[Cd2Cl6(OH2)2](C4H12N2) }n (1) are reported. Optimization of crystal growth parameters is discussed to achieve bulk single crystal with reduced crystal defects by slow solvent evaporation technique. The acid hydrolysis of the piperazine molecule during the pH optimization converted it into piperazine-1,4-diium, which is neutralized by [Cd2Cl6(OH2)2 ]2- via hydrogen bond interactions. The intermolecular charge transfer responsible for optical nonlinearity in 1 is proved possible by calculating the intermolecular interaction energies at HF/321G level of quantum mechanical calculations. The two-photon absorption coefficient measured at different nanosecond pulsed laser intensities is found to vary, which explicitly confirmed sequential 2 PA in 1. Lower optical limiting threshold of 1 measured under CW and nanosecond pulsed green laser regime ((1.027 +/- 0.02) x 103 Wcm-2 and (1.87 +/- 0.02) x 1012 Wm-2 respectively) with coherent dielectric, thermal, mechanical, linear absorption and emission properties showed its suitability for an efficient optical limiting device application.