This project presents a computational study of the effects of solvents and NO₂substituent (at the ortho, meta, para position) on the electronic and optical properties of three schiff bases : 4-(((4-((2-nitrobenzylidene)amino)phenyl)imino)methyl)phenol (2-NBP), 4-(((4-((3-nitrobenzylidene)amino)phenyl)imino)methyl)phenol (3-NBP), and 4-(((4-((4-nitrobenzylidene)amino)phenyl)imino)methyl)phenol (4-NBP) to provide information on new materials with an easier synthetic and more economical route which can play a role in optical applications.

The time-dependent density functional theory (TD-DFT) at B3LYP/6-31G (d, p) level has been utilized for the investigation of the compounds in the gas phase and in solution (hexane, ethanol, acetonitrile, dichloromethane, methanol and tetrahydrofuran) using a polarizable continuum model. Quantum chemical, linear and nonlinear optical parameters such as frontier orbital energies, energy gap ΔE, electric dipole moment (μ), static dipole polarizability (α), first hyperpolarizability (β_tot) and second hyperpolarizabilty (γ) were computed and analyzed. The nonlinear optical properties of urea was used as the standard for the comparison with that of the investigated Schiff bases at the same level of theory.

The analysis of the results showed that these properties are altered based on the solvating medium and position of the electron withdrawing group. It was observed that the dipole moments and polarizabilities for the three schiff bases are enhanced as the energy band gap decreased and this is associated with an increase in the polarity of the solvent. The first order hyperpolarizability for 2-NBP, 3-NBP, and 4-NBP are respectively 6 times, 17 times, and 27 times higher than that of urea while the second order hyperpolarizability are respectively 80 times, 102 times, and 124 times higher than that of urea.

The results confirm that these molecules have good prospects in optoelectronic and electronic applications, and 4-NBP in a polar environment is seen to be the most promising.

Olaide Adeyemi

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