Theoretical Studies on The Structural, Vibrational, Conformational Analysis and Nonlinear Optic (NLO) Property of 4-(Methoxycarbonyl) Phenylboronic Acid

Abstract

In this paper, the structural, electronic, non-linear optical (NLO) properties and vibrational frequencies of 4-(methoxycarbonyl) phenylboronic acid has been examined theoretically using ab initio Hartree-Fock (HF) and Density Functional Theory (DFT/B3LYP) methods applying the standard 6-311++G(d,p) basis set. ¹H- and ¹³C-chemical shifts were calculated by employing the direct implementation of the gauge including-atomic-orbital (GIAO) method at the B3LYP/6-311++G(d,p) and HF/6-31G(d) levels of the theory. There are two conformers, (cis-trans = ct) and (trans-cis = tc) for title molecule. The energy difference between ct and tc conformers of studied molecule are of 0.126 kcal/mol with B3LYP/6-311++G(d,p) and 0.138 kcal/mol with HF/6-311++G(d,p), respectively. The conformer ct is more stable than the conformer tc. Also, the energy gap (ΔΕg) differences between the highest occupied (HOMO) and lowest unoccupied molecular orbitals(LUMO), dipole moment, polarizability and first static hyperpolarizability were calculated as a function of both dihedral angle (C3-C4-C7-O3), between methoxycarbonyl group (CH₃-O-CO-) and benzene ring, and dihedral angle (C2-C1-B-O1), between boronic acid group (-B(OH)₂) and benzene ring. In the change of the energy gap and polarizability depending on dihedral angles, it was shown that the polarizabilities were follow inverse relationship the energy gaps.