Synthesis and Spectral Characterization of Some Transition Metal Complexes Containing Pentadentate SNNNS Donor Heterocyclic Schiff Base Ligands

Abstract

A new Schiff base, 2,6-diacetylpyridine bis(3-methylsulfhydryl-4-amino-5-mercapto-1,2,4-triazole) (DPMAMT) is designed and synthesized by the condensation of 2,6-diacetylpyridine with 3-methylsulfhydryl-4-amino-5-mercapto-1,2,4-triazole, and structurally characterized. Copper(II), cobalt(II), nickel(II), manganese(II), zinc(II), cadmium(II) and oxovanadium(IV) complexes of DPMAMT have been prepared for the first time, and characterized on the basis of elemental analyses, conductance measurements, magnetic properties, spectral (i.r., 1 H-n.m.r., u.v.-vis., e.p.r. and FAB-mass) and thermal studies. The complexes exhibit an octahedral geometry around the metal center. The pentadentate behavior of the ligand was confirmed on the basis of spectral studies.

Synthesis, Spectroscopic Characterization, Thermal Investigation and Antimicrobial Activity of S, O and N-Donor Heterocyclic Schiff Base Ligands and their Co(II), Cd(II), Hg(II), Fe(III) and UO2(II) Metal Complexes

“…These data are close to that reported for three and five unpaired electrons. Cd(II), Hg(II) and UO 2 (II) complexes are diamagnetic as expected for d 10 system (1,29,30) .…”

“…The reaction of ligands under study, L 1 -L 3 with Co(II), Cd(II), Hg(II), Fe(III), and UO 2 (II) ions afforded the mononuclear metal complexes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The structure of the isolated complexes are discussed on the basis of their elemental analysis, conductance, IR, electronic spectral data, mass spectra and magnetic moment measurements.…”

“…These new bands indicate a good evidence for the participation of O, S and N donors in complex formation. Additionally, the position of ν asy (OCO) and ν sy (OCO) bands at 1575 -1436 cm -1 and 1375 -1208 cm -1 , respectively in the IR spectra of acetato complexes, (1,3,6,8,11,13) as well as their difference, Δ > 185 cm -1 are characteristic for the monodentate coordination mode (24) . The nitrato complexes, (2,10,12,15) show three bands at 1492 -1404 cm -1 , 1374 -1234 cm -1 and 1170 -1026 cm -1 corresponding to unidentate coordination mode of nitrate group while the complexes, (4, 5, 7, 9, 14) have a characteristic strong absorption band at 1384 -1382 cm -1 and medium band at 815-764 cm -1 assigned to ionic nitrate, additionally complexes (4,5,7,9,14) show three bands at 1485-1442 cm -1 , 1296 -1200 cm -1 and 1166 -1020 cm -1 corresponding to unidentate coordination mode of nitrate group (25)(26)(27) .…”

“…The spectra of the ligand, L 2 shows a signal at about δ 3.4 ppm (1H,s) attributed to SH protons (15,16) , this signal in metal complexes, (7,8) is shifted to up or/and downfield which indicates that the SH group may participate in coordination without proton displacement. The spectra of the ligand, L 3 show signal due to pyridine protons at δ 7.9-6.3 ppm (multiplets) (1) . In metal complexes, (12,13), the upfield shift of these signals suggest the participation of pyridine nitrogen in coordination to the metal ions.…”

“…The condensation of primary amines with carbonyl compounds are referred to as Schiff bases (1)(2)(3)(4) . Schiff bases play an important role in inorganic chemistry as they easily form stable complexes with most transition metal ions (5) .…”