Crystal structures, electrochemical properties and theoretical studies of three New Zn(II), Mn(III) and Co(III) Schiff base complexes derived from 2-hydroxy-1-allyliminomethyl-naphthalen

Abstract

Three novel complexes of the Schiff base, 2-hydroxy-1-allyliminomethyl-naphthalen (HL), namely ZnII(HL)2 (1), polymeric [(MnIII(HL)2)(N3)2]n (2), and CoIII(HL)3 (3) were synthesized from the reaction of ZnBr2•2H2O, MnCl2•2H2O and Co(OAc)2•4H2O with the Schiff base ligand. The complexes were characterized by elemental analysis, FT-IR, UV-vis, as well as by the single-crystal X-ray diffraction technique. In all these complexes, central metal ions were coordinated by O and N atoms of the Schiff base ligand. It was found that the Zn complex (1) was C2-symmetrical, with the Zn ion in quite a regular tetrahedral environment. In turn, the Mn complex (2) made 1D-coordination polymer with N3 linkers between also symmetrical (Ci) Mn(HL)2 monomers, with six-coordinated Mn ion in an octahedral environment. Finally, the Co ion in Co(HL)3 complex (3) was also octahedrally 6-coordinated. Additional solvent (DMSO) molecules are built in the crystal architecture. The electrochemistry of complexes in DMSO displayed a metal-centered reduction peak corresponding to the ZnII/I- ZnI/0, MnIII/II- MnII/I, and CoIII/II - CoII/I at (-1.15,-1.53), (-0.11,-1.79) and (-0.76, -1.69) V, respectively. The molecular geometry of the complexes was optimized using the density functional theory with the basic set (B3LYP / 6-311G). After optimal DFT, the electron transfer spectrum was calculated theoretically and compared with the experimental results. Hirshfeld surfaces and fingerprint plots are used to visualize and analyze intermolecular interactions. The Hirshfeld surface analysis showed that the crystal cohesion of the structures of the three complexes is established via H•••H, C•••H/H•••C, and O•••H/H•••O the dominant contacts. As well as, molecular docking studies were carried out for all complexes to find their binding affinity with protein (PDB ID: 1LRI). Molecular binding studies have shown good interaction with the intended drug targets.