Spectroscopic behavior, FMO, NLO and NBO analysis of two novel aryl boronic acid derivatives: Experimental and theoretical insights

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Here we report, experimental and theoretical determination of ground and excited state dipole moments of aryl boronic acid derivatives, 2-Bromophenyl boronic acid (2BPBA) and 2-Isopropylphenyl boronic acid (2IPBA). In both the compounds, Bathochromicshift is observed with increasing solvent polarity indicating π →π* transition due to intermolecular charge transfer interactions. For both the compounds, the ground and excited sate dipole moments are parallel to each other. The excited state dipole moment (μe) is greater than ground state dipole moment (μg) for the compound 2IPBA where as for 2BPBA, excited state dipole moment (μe) is less than ground state dipole moment (μg). Further, experimentally obtained Δμ are compared with those using microscopic empirical solvent polarity (ETN). In parallel, the use of Kamlet-Taft parameters to the solvent effect on spectral properties of 2BPBA and 2IPBA are also discussed. The molecular structure, Frontier Molecular Orbitals (FMO), Natural Bond Orbital (NBO) analysis, Non-Linear Optical (NLO) properties of 2BPBA and 2IPBA have been investigated using the (DFT) calculations with B3LYP/6‒311++G (d, p) basis set. The chemical reactivity and kinetic stability of the compounds is shown by differences between the energy levels by analyses of Frontier molecular orbitals. The polarizability and hyperpolarizability computations determine the NLO properties, whereas Natural bond orbital (NBO) analysis showed proton transfer within the selected donor-acceptor depicting large energy of stabilization for the compounds under study.