Structural analysis and nonlinear optical properties of boronyl-based Schiff base liquid crystalline series: a theoretical study

Schiff base liquid crystal (LC) compounds are anisotropic, typically possessing smectic phases. In this work, we design and study a new series of Schiff bases, nBO (n = 1–9), featuring two core rings connected via an azomethine group with boronyl and alkoxy as terminal groups, using density functional theory (DFT) and time-dependent DFT (TD-DFT). These nBO molecules are rod-like, having the length–to–breadth ratio close to 3 and a dihedral angle between rings close to 1530. Their chemical reactivity and dipole moments increase sharply up to n = 3 and slowly for n = 4–9. The mean polarizability of nBO increases linearly with an increase in the length of the alkoxy chain (n). Similarly, their first static hyperpolarizability increases from 4.8 × 103 a.u. (n = 1) to 6.1 × 103 a.u. (n = 9), establishing their strong nonlinear optical (NLO) responses, which are explained on the basis of electronic transition in crucial excited states. These findings are useful for the applications in nonlinear optics and optoelectronics.