Metal Complexes of Novel Symmetrical Schiff Base Ligands

Abstract

Two novel symmetrical Schiff base ligands, H 2 L 1 and H 2 L 2 , with tetradentate N 2 O 2 and pentadentate N 3 O 2 coordinating sites were prepared by the reaction of the aldehyde 2-methyl-7-formyl-8-hydroxy-quinoline with 1,3-diaminopropane or diethylenetriamine, respectively, in the molar ratio 2:1. Cu(II), Ni(II), Co(II), Mn(II), Fe(III) and VO(IV) complexes of both ligands were synthesized. The ligands and their metal complexes were characterized by elemental analyses, IR, UV-Vis, ESR, NMR and mass spectra and also by magnetic moment measurements. Both ligands behave as tetradentate ones when coordinating metal cations. The ligand H 2 L 1 has a smaller cavity than the ligand H 2 L 2 , thus the former ligand yielded mononuclear products, through chelation of one ligand molecule to a metal cation, while the latter ligand yielded binuclear products, through the coordination of two metal cations to two ligand molecules. Each of the Fe(III) cations was coordinated to three halves of both ligand molecules yielding also a mononuclear product with ligand H 2 L 1 and a binuclear product with ligand H 2 L 2 . Either mononuclear or binuclear complex molecules link together forming polymeric chains. The mononuclear and binuclear complex forms were well manifested in the ESR spectra of the vanadyl complexes. The polymeric structures of the metal complexes led to an enhanced decrease of their magnetic moments through antiferromagnetic exchange between neighbouring metal cations.

Binuclear Co(II), Ni(II) and Cu(II) Complexes of a new Bis(tridentate) Hydrazone Ligand: Synthesis, Thermal, Spectroscopic, Biological, Molecular Docking and Theoretical Studies

“…The effective magnetic moment of Co-DHNAPH complex is 3.52 B.M. which is lower than expected for octahedral Co(II) complexes suggesting an antiferromagnetic interaction between Co(II) ions [78][79][80].…”

Characterization and Thermal Analysis of Mercury Complexes Containing Intermolecular N→Hg Interactions

“…In addition, the low energy absorption peaks in the wavelength range 380-391 nm are associated with a charge transfer transition. The spectra of the complexes do not show any d-d transitions 15,16 .…”

Enzyme inhibition, radical scavenging, and spectroscopic studies of vanadium(IV)–hydrazide complexes

“…This may be attributed to a lowered magnetic moment due to antiferromagnetic coupling 40,41 . Several reports exist in the literature of oxovanadium(IV) binuclear complexes that exhibit magnetic moments in the range reported here 42,43 .…”