Transition metal complexes with thiosemicarbazide-based ligands, Part 58. Synthesis, spectral and structural characterization of dioxovanadium(V) complexes with salicylaldehyde thiosemicarbazone

Abstract

The first two complexes of dioxovanadium(V) with salicylaldehyde thiosemicarbazone (SALTSC), of the coordination formulas [VO 2 (SALTSC--H)]·H 2 O (1) and NH 4 [VO 2 (SALTSC-2H] (2), were synthesized and characterized by elemental analysis, conductometric measurements, IR and UV-Vis spectroscopy and X-ray analysis. The complexes were obtained in the reaction of an aqueous ammoniacal solution of NH 4 VO 3 and SALTSC. The results of the characterization showed that SALTSC was coordinated in the usual ONS tridentate mode as monoanion in complex 1 and dianion in complex 2. In both complexes, the vanadium atom is in a deformed square-pyramidal environment and is slightly shifted towards the apical oxo-ligand (≈ 0.52 Å).

Synthesis, Structures, and Solution Studies of a New Class of [Mo2O2S2]-Based Thiosemicarbazone Coordination Complexes

“…In these two molecular structures, unexpectedly for this class of ligands, the ligands do not act as classical tridentate ONS donors. Indeed, in contrast with the number of complexes in the literature, the −OH function of the R1 group remains protonated and noncoordinated to the metal, while it is usually deprotonated and coordinated in 3d transition metal complexes. ,, …”

“…Indeed, in contrast with the number of complexes in the literature, the −OH function of the R1 group remains protonated and noncoordinated to the metal, while it is usually deprotonated and coordinated in 3d transition metal complexes. 20 , 58 , 61 …”

“…Indeed, in contrast with the number of complexes in the literature, the −OH function of the R1 group remains protonated and noncoordinated to the metal, while it is usually deprotonated and coordinated in 3d transition metal complexes. 20,58,61 Furthermore, the configuration of the ligand in both complexes could be stabilized by intramolecular contacts between the N imino group with the −OH group from R1 Structures with "Group III" Ligands. Finally, for the last category of ligands represented by HL 13 , the molecular complex of a 1:2 stoichiometry gives a trans-type isomer with 2 monodeprotonated (L 13 ) − ligands in which the thiophene group is found to be free, in agreement with the structures obtained with HL 1 , HL 2 , H 2 L 8 , and H 2 L 12 ligands, and the coordination spheres of the two Mo(V) centers are ensured by the thiolate groups and the imine group of the ligand (Figure 6), while the imine was found uncoordinated in almost all of the other complexes.…”

Synthesis, Spectral and Thermal Characterization of Selected Metal Complexes Containing Schiff Base Ligands with Antimicrobial Activities

“…The band at 1616 cm -1 due to the azomethine υ(C=N) stretching frequency of the free ligand that shifted to a lower frequency in the spectra of the Ni(II) complex (figue-13) at 1607cm -1 indicating the coordination through N atom [5][6][7][8][9]. The band 3444 cm -1 due to the υ (O-H) of the hydroxyl group in the IR spectra of the ligand was absent and shifted to lower absorption frequency in the IR spectra of Ni(II) complex indicated the coordination through the phenolic oxygen [22,24]. This is confirmed by the shift of υ(C-O) stretching vibration observed at 1266 cm -1 in the spectra of free ligand to 1294 cm -1 stretching vibration of complex after coordination [16], which corresponds to forming of weaker C-O(Ni) bond comparing to C-O(H) and confirms coordination of ligand to Ni(II) via deprotonated phenolic oxygen.…”

Complexes of pyridoxal thiosemicarbazones formed with vanadium(IV/V) and copper(II): Solution equilibrium and structure

“…This leads to a zwitterionic ligand structure with one positively charged pyridinium nitrogen and the negatively charged deprotonated phenolic oxygen and thiolate sulfur atom, generating together with the vanadium(V) ion neutral metal complexes. In contrast, vanadium(V) complexes with the closely related STSC ligands in the thiolate form are usually positively charged [53,54]. …”