Theoretical Model of a Nematogen: Estimation of Phase Stability, Absorption, Electrochemical, and Nonlinear Optical Properties

Theoretical analysis has been presented on a nematogen 4-dimethylaminobenzaldehyde (4-cyano-phenylethylidene) hydrazone (E,E) (C18H18N4) to analyze its phase stability. The net atomic charges and dipole moment at each atomic centre has been calculated using complete neglect of differential overlap/spectroscopy method. The modified Rayleigh-Schrodinger perturbation theory along with multicentered-multipole expansion method has been used to evaluate the long-range intermolecular interactions. A 6-exp potential function has been used for short-range interactions. The total interaction energy values have been used as input to calculate the probability of a particular configuration using the Maxwell-Boltzmann formula. Further, the Helmholtz free energy, and entropy at room temperature (300 K), nematic-isotropic transition temperature (436 K) and above transition temperature (500 K) have been computed. An attempt has been made to understand the phase stability and behaviour of the molecule. UV absorption spectra have been calculated using complete neglect of differential overlap/spectroscopy, and intermediate neglect of differential overlap/spectroscopy methods. The observed pi ->pi* transitions, electrochemical properties based on highest occupied molecular orbital, lowest unoccupied molecular orbital energies, and principal polarizability components, and anisotropy of polarizability have been reported to understand the kinetic stability, global reactivity, and non-linear optical activity of the molecule.