Synthesis, structural analysis and investigation of nonlinear optical properties of some transition metal complexes containing 2-pyridinecarboxylic acid

In this study, seven transition metal complexes which contain picolinic acid {[Co(pic)2(H2O)2]•2H2O, [Zn(pic)2(H2O)2]•2H2O, [Ni(pic)2(H2O)2]•2H2O, [Mn(pic)2(H2O)2], [Cu(pic)2]•2H2O, [Cu(pic)2(phen)]•H2O and [Mn(pic)2(phen)]•H2O} were synthesized and their structural characterizations were carried out by X-Ray diffraction and density functional theory (DFT) methods. The synthesized picolinate complexes have distorted octahedral geometry coordination sphere. The vibrational properties of synthesized picolinate complexes were investigated by recording FT-IR and Raman spectra. UV-Vis spectra for picolinate complexes were recorded in ethanol solvent, and the electronic absorption bands were determined. In order to support experimental data, IR, Raman and UV-Vis spectra were calculated by using DFT//B3LYP metod and 6-311++G(d,p) basis set for C, H, N and O atoms and LanL2DZ basis set for metal ions. When the obtained theoretical results were compared with experimental ones, it is seen that there is a good agreement between them. Gaussian 09 Revision D.01 package program was used in theoretical calculation part. The important contributions to electronic transitions from molecular orbitals were designated by using SWizard program. The HOMO, LUMO and other molecular orbitals, which are active in electronic transitions, have been calculated. The quantum mechanical parameters such as, electronegativity, chemical potential, chemical hardness and softness were obtained by using calculated HOMO and LUMO energies. Additionally, the spin density distributions of the synthesized complexes were also examined. Natural bonding orbital (NBO) analysis was performed by using DFT//B3LYP method and 6-311++G(d,p)-LanL2DZ basis set. Mulliken, NBO and APT charges for picolinate complexes were computed and compared with each other. Finally, dipole moment (μ), the average polarizability (<α>), anisotropy of polarizability (Δα) and the first order static hyperpolarizability (<β>) parameters which are the indicators of the nonlinear optical (NLO) properties have been calculated.