Synthesis, Crystal Structure, Fluorescence and Theoretical Calculations of Three Zn(II)/Cd(II) Complexes with Bis-dentate N,N-Quinoline Schiff Base

Three d¹⁰ metal complexes, ZnL(OAc)₂ (1), CdL(OAc)₂ (2) and [CdL₂(NO₃)₂]·CH₃CN (3) were synthesized using the ligand (E)-N-(3-methoxy-4-methylphenyl)-1-(quinolin-2-yl)methanimine (L) and characterized by FT-IR spectra, NMR spectra, and CHN elemental analysis. Single-crystal X-ray diffraction analysis revealed that complexes 1 and 2 are isostructural, with the central metal adopting a hexacoordinate octahedral geometry, while complex 3 adopts a triangular dodecahedron geometry. Thermal gravimetric analysis showed that these complexes exhibit good thermal stability. Solid-state fluorescence spectroscopy measurements demonstrated that complexes 1–3 exhibit bright yellow-green fluorescence (λ_em = 564 nm for 1; 524 nm for 2; 542 nm for 3), suggesting their potential as photoluminescent materials. Furthermore, DFT calculations, including frontier molecular orbitals, energy levels, and surface electrostatic potential, provided insights into the structural and electronic spectral properties of complexes 1–3.

Three d¹⁰ metal complexes have been synthesized using bis-dentate N,N-quinoline Schiff Base and their structures, fluorescence properties, as well as theoretical calculations were further characterized and discussed.