Novel Mn(II) and Zn(II) Complexes of 6-Bromopicolinic Acid as a Potential Optical Material: Synthesis, Spectral Characterizations, Linear, and Nonlinear Optical Properties and Density Functional Theory Calculations

Abstract

The Mn(II) and Zn(II) complexes of 6-bromopicolinic acid (6-BrpicH) were synthesized for the first time, and their molecular structures were determined by X-ray diffraction (XRD) technique. The detailed experimental spectral studies were executed by Fourier-transform infrared (FT-IR) and UV-Vis spectra. The experimental optical properties, such as refractive index, linear polarizability, optical susceptibility, optical band gap, extinction coefficient, dielectric constant, and volume energy loss function (VELF) and surface energy loss function (SELF) parameters obtained from the transmission spectra with solution technique in ethanol solvent of these complexes, were investigated. Additionally, the refractive index (n), optical band gap, chi((1)) (linear optical susceptibility), chi((3)) (third-order nonlinear optical susceptibility), and first- and second-hyperpolarizability (beta and gamma) parameters were surveyed by using density functional theory (DFT)/HSEh1PBE/6-311G(d,p)/LanL2DZ level. The experimental and theoretical optical band gap energies of complex 2 were obtained at 4.26 and 4.67 eV. The experimental and theoretical n values of complex 1 in the mid-IR region were found to be 1.581 and 1.58 (in gas phase). The experimental linear optical alpha over bar and chi((1)) parameters were calculated at 31.73 x 10(-24) and 14.58 x 10(-2) esu for complex 1 in the mid-IR region; the corresponding theoretical parameters for complex 1 in the gas phase were obtained at 36.07 x 10(-24) and 18.35 x 10(-2) esu. The second-order nonlinear optical (NLO) results exhibit that complex 1 is a promising candidate to materials with the high second-order hyperpolarizability values obtained as 540.71 x 10(-36) and 56.83 x 10(-36) esu in ethanol solvent and gas phase. Moreover, the intermolecular and intramolecular bonding and the definition of coordination geometries around the central metal ions, as well as the electronic charge transfer interactions in the Mn(II) and Zn(II) complexes, were confirmed by natural bond orbital (NBO) analysis. To sum up, the detailed experimental and theoretical structural, spectroscopic, electronic, and optical properties of the synthesized complexes were comparatively presented.