Influence of Co(II) and Cd(II) metal ions on structural, electronic and nonlinear optical properties of 4-methoxypyridine-2-carboxylic acid complexes: An experimental and computational study

Abstract

Molecular engineering of metal-organic frameworks has attracted increasing attention due to their potential technological applications in the fields of optics and photonics. Therefore, a number of organometallic complexes are investigated for nonlinear optical applications. The current research aimed to synthesize and investigate spectroscopic and nonlinear optical properties of two metal-organic coordination compounds, namely Co(MeOPic)2∙(H2O)2 and Cd(MeOPic)2∙(H2O)2. The FT-IR and UV-Vis spectra for the distorted octahedral Co(II) and Cd(II) complexes were recorded. In order to provide a deep understanding about the relation between structure and nonlinear optical properties, density functional theory studies were also applied to both of the complexes by using B3LYP/6–311++G(d,p)/LanL2DZ level. TG-DTA analysis demonstrated that Cd(II) complex is approximately stable up to 134 °C, and the same complex only loss the aqua ligands between 134 and 189 °C. Therefore, the main skeleton part continues to remain stable up to 208 °C. Static NLO studies also demonstrated that both complexes have weak responses due to centrosymmetric structures, while Co(II) complex is appropriate to third-order NLO applications (γ (0;0,0,0) = 148.70×10−36 esu and γ (-2w;w,w,0)=-1521.4×10−36 esu).