Preparation, crystal structures, properties, and time-dependent density functional theory of two cobalt complexes with 3-hydroxy-2-methyl-quinoline-4-carboxylate

One organic compound [HMCA]2 (1) and two novel cobalt complexes [Co(MCA)(bipy)(H2O)]·(H2O) (2), [Co2(MCA)2(Phen)3]·3(H2O) (3) are synthesized by a solvothermal approach and are structurally determined by single-crystal X-ray diffraction. Compound 1 exhibits a two-dimensional structure by hydrogen bond and π. . .π stacking interaction. The complexes exhibit a three-dimensional and one-dimensional metal-organic framework. Solid-state photoluminescence spectrums reveal that they show blue emission bands at 449 nm, and theoretical calculation results of time-dependent density functional theory show that all belong to ligand-to-ligand charge transfer. Solid-state diffuse reflectance spectrums reveal the presence of a narrow optical band gap of 1.72 and 1.60 eV in the complexes 2 and 3, respectively.