Synthesis, structures, and property studies on Zn(II), Ni(II), and Cu(II) complexes with a Schiff base ligand containing thiocarbamide group

Abstract

A Schiff base ligand containing thiocarbamide group of 4-phenyl-1-(4-methoxyl-1-phenylethylidene)thiosemicarbazide (HL) and its three mononuclear metal complexes of ZnL 2 (1), NiL 2 (2), and CuL 2 (3) have been synthesized. Elemental analysis, IR, and X-ray single crystal diffraction characterizations for the ligand and the three complexes have been carried out. In the three complexes, the central metallic ions of Zn 2? , Ni 2? , and Cu 2? coordinate with two deprotonated ligands of L -, respectively. In 1, Zn 2? ion adopts a distorted tetrahedral geometry, while in 2 and 3, both the Ni 2? and Cu 2? ions possess distorted square planar configurations. For the four compounds, UV-Vis spectra have been measured and DFT calculations at B3LYP/LANL2DZ level of theory prove that the electronic spectra of HL and 1 are corresponding with electronic transitions of n ? p* and p ? p* in the ligand itself and the electronic spectra of 2 and 3 are attributed to intraligand electronic transitions as well as d-d electronic transitions. Electrochemical investigations reveal that the different metal-ligand interactions have changed the peak shapes and peak locations, which are corresponding with the DFT-B3LYP/LANL2DZ calculational results. Fluorescence spectra measurements indicate that the ligand emits purple fluorescence and the complex 1 emits stronger blue fluorescence, while the complexes 2 and 3 quench fluorescence. The thermal analyses result show that the three complexes undergo two similar decomposition processes because of their similar geometric configurations.

Zn(ii) complex with 2-quinolinecarboxaldehyde selenosemicarbazone: synthesis, structure, interaction studies with DNA/HSA, molecular docking and caspase-8 and -9 independent apoptose induction

“…41 In the cyclic voltammogram of 1 the corresponding cathodic peaks are shied to positive positions (À1.35 and À1.84 V vs. Ag/AgCl) due to the metal-ligand orbital interactions, as was noticed for the Zn complex with 4-phenyl-1-[(4-methoxyphenyl)methylene]-thiosemicarbazide. 42 In the range from 0 to À1.3 V additional reduction peaks are observed in the cyclic voltammogram of 1, as in the case of the Zn-benzil bis(thiosemicarbazone) complex. 40 The number of reduction peaks is equal for Hqasesc and 1 which indicates that the complex is stablethe Zn(II) ion is "hidden" for reduction in the chelate structure.…”

Series of Dicyanamide-Interlaced Assembly of Zinc-Schiff-Base Complexes: Crystal Structure and Photophysical and Thermal Studies

“…The presence of electronically saturated Zn II ion is necessary because it imposes conformational rigidity to the ligand and prevents energy loss via bond vibration and electron transfer processes, 11 whereas paramagnetic transition metals quench fluorescence by different electron/energy transfer mechanisms. 12,13 Our group has previously synthesized luminescent complexes of different salicylaldimino Schiff bases with zinc 11,14,15 as well as lanthanoids. 16 As part of our efforts of searching for new luminescent materials, we have designed some conjugated aromatic Schiff bases by the condensation of 1,3-diamines and a few substituted salicylaldehydes (Scheme 1) to investigate the effect of electron donating and withdrawing groups on their luminescence properties.…”

“…Zinc complexes of salicylaldimino Schiff bases are found to be promising materials to serve this purpose. , This particular type of Schiff bases has close resemblance to 8-hydroxyquinoline with respect to conjugation and chromophoric groups and is expected to promote luminescence properties of the Zn II complexes which actually originates from the ligand centered excited states rather than LMCT. The presence of electronically saturated Zn II ion is necessary because it imposes conformational rigidity to the ligand and prevents energy loss via bond vibration and electron transfer processes, whereas paramagnetic transition metals quench fluorescence by different electron/energy transfer mechanisms. , Our group has previously synthesized luminescent complexes of different salicylaldimino Schiff bases with zinc ,, as well as lanthanoids . As part of our efforts of searching for new luminescent materials, we have designed some conjugated aromatic Schiff bases by the condensation of 1,3-diamines and a few substituted salicylaldehydes (Scheme ) to investigate the effect of electron donating and withdrawing groups on their luminescence properties.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…In the experimental study by Zhao et al [240], synthesis and characterization including X-ray single crystal structures of Schiff base ligand 4-phenyl-1-(4-methoxyl-1-phenylethylidene)thiosemicarbazide (HL) and its chelate complexes, ZnL 2 , NiL 2 , and CuL 2 are reported. While so complexed Zn(II) ion adopts a distorted tetrahedral geometry, Ni 2?…”