Investigation of Substitute Effect on Non-Linear Properties, Conformational, Vibrational and Electronic Structure of 2-Methoxypyridine-3-Boronic Acid by Quantum Mechanical Methods

In this study, the values of structural parameters, vibration frequencies, dipole moment (μ), polarizability (α), hyperpolarizability β) of 2-methoxypyridine-3-boronic acid (I) and 6-substituted-2-methoxypyridine-3-boronic acid derivatives; 6-fluoro-2-methoxypyridine-3-boronic (II) and 6-chloro-2-methoxypyridine-3-boronic acid (III) molecules have been calculated at Hartree Fock (HF) and Density Functional Theory (DFT / B3LYP) with 6-311++G (d, p) basis set. The highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) of I, II ve III molecules have been computed and their respective gap (ΔEg) have been examined. The 1H and 13C NMR chemical shift values were calculated in gas phase by GIAO approach using B3LYP/6-311+G (2d,p) and HF/6-31G (d) level of theory. In addition, the potential energy surface (PES) of the molecules as a function of the dihedral angle (C1-C2-B-O1) have been carried out using the 6-31+G basis set in both methods. There are minimums at 0？, 140？, 220？ and 360？, maximums at 90？, 180？ and 270？ on the calculated potential energy surfaces. The order of the hyperpolarizability values of the molecules is III> II> I. It was seen that I molecule had at the maximum barrier height at 180？. The dipole moment values of molecules I, IIand IIIare found as 1.18, 1.19 and 1.25 at B3LYP / 6-311++G (d, p) method-basis set combination and 1.17, 1.16 and 1.30 Debye at HF / 6-311++G (d, p) method-basis set combination, respectively. The structural parameters of the Imolecule, which were calculated by both methods, were compared with the data in the literature and there was a good agreement between the structural parameters