Exploration of Structural, Electronic and Third Order Nonlinear Optical Properties of Crystalline Chalcone Systems: Monoarylidene and Unsymmetrical Diarylidene Cycloalkanones

Abstract In the current study monoarylidene and unsymmetrical diarylidene cycloalkanes, MBMHP, MABP, MBHP, and MBCP have been prepared. Their molecular structures were confirmed by SC-XRD. Accompanying the experimental studies, quantum chemical investigation is performed at the M06/6-311+G(d,p) level, with the natural bond orbital analysis (NBO) performed at the ωB97XD/6-311+G(d,p) level. NBO study showed that the hyper-conjugation and intermolecular charge transfer play a remarkable role in stabilizing the crystals and also endorsed the SC-XRD investigations. Furthermore, the band gap of orbitals explained the chemical reactivity and charge transfer phenomena in the above-mentioned crystals. The smallest HOMO/LUMO band gap (4.127 eV) is exhibited by MABP molecule while the highest gap value is found for MBHP to be 4.768 eV.. Global reactivity parameters (GRP) are also explored from the energies of HOMO/LUMO. Among all crystals MBHP has higher value of hardness (η = 2.384 eV) while MABP showed higher global softness (σ=0.242307 eV). So, from GRP it is revealed that all the studied crystals are less reactive but more stable as suggested by NBO and SC-XRD investigations. NLO study showed that the crystal MBMHP has the higher value of linear polarizability and second hyperpolarizability γ > 216.36 and 1.06×104 a.u respectively, among all the synthesized crystals. NLO properties of these synthesized crystals may play a significant contribution for the NLO technological applications.