Nickel(II) complex of [NiL2](ClO4)2, where L is an unsymmetrical tridentate ligand of 2-(2-aminoethyl)imino-3-butanone oximehas been synthesized by a template condensation reaction. The complex was characterized on the basis of microanalytical, spectroscopic, and other physicochemical properties. X-ray diffraction study of the complex reveals nickel(II) center in a distorted octahedral environment through two amine nitrogen donors, two imine donors,and two nitrogen atoms of the oxime moieties of the ligand. The antibacterial activity of the complex has been tested against Gram(+) and Gram(-) bacteria. The results of the antibacterial screening indicated that the complex is effective against bacterial growth retardation activity to some extent and its effectiveness is higher forGram(+) bacteria.

In this research, the tridentate Schiff base ligand N2O was prepared and then the 1D Cu(II) ‎coordination ‎polymer was synthesized. The ligand and polymer were characterized via analytical and ‎spectral methods. The ‎crystal structure of polymer was determined by single crystal X-ray diffraction ‎method. It was exhibited that ‎the Cu(II) ion was surrounded by tridentate Schiff base ligand and ‎acetate ion, produced distorted octahedral ‎geometry. Two nitrogen atoms( one aminic ‎nitrogen atom and one iminic nitrogen atom) and one phenolic ‎oxygen atom from tridentate Schiff ‎base ligand and two oxygen atoms of acetate ion coordinated to the Cu(II) ‎ion. One of the oxygen ‎atoms was simultaneously coordinated to two Cu(II) ions and caused the formation of ‎the linear ‎coordination polymer. The antibacterial activity of the ligand and coordination polymer was ‎‎investigated against the Klebsiella pneumoniae‎‏‎,‎‏ ‏‏‎ Salmonella enterica bacteria and the results showed ‎that the ‎ligand was exhibited higher activity than the polymer. ‎

For the preparation of the ligand, 2-((2-(2-(pyridine-2-ylmethyleneamino) phenylthio)ethylimino)methyl)phenol (HL), at first, unymmetric thioethere amine 2-(2-aminoethylthio)-N-(pyridine-2-ylmethyleneanilin) has been prepared through nucleophilic substitution of 2-aminothiophenol with N-(2-bromoethyl)phthalimide, then condensed with pyridine-2-carbaldehyde and then phthalimide group removed with hydrazine hydrate. Then Schiff base ligand HL was prepared via condensation of this unsymmetrical thioether amine with 2-hydroxybenzaldehyde. Mn(II), Co(III), Ni(II), Cu(II) and Cd(II) Schiff base complexes of this ligand have been synthesized. The thioether amine and unsymmetrical Schiff base ligand were characterized by appropriate spectroscopic methods such as IR, 1H NMR, 13C NMR studies, and also unsymmetrical Schiff base complexes were characterized by IR, UV-Vis,  molar conductivity and elemental analysis methods.

The rhenium(I) compound fac-[Re(CO)3(daa)].Hpab.H2O (Hpab = N,N''-(1,2-phenylene)bis(2''-aminobenzamide); Hdaa = 2-amino-N-(2-aminophenyl)benzamide) was synthesized from the reaction of [Re(CO)5Br] with two equivalent of Hpab in toluene. The monoanionic tridentate ligand daa was formed by the rhenium-mediated cleavage of an amido N-C bond of the potentially tetradentate ligand Hpab. The compound was characterized by IR spectroscopy and X-ray crystallography, and daa is coordinated as a diaminoamide via three nitrogen-donor atoms.

Schiff base transition metal complexes using benzil and its derivatives as a diketone with different amines in 1:1 or 1:2 ratio can be synthesized by simple condensation reaction or mild conditions. They may contain donor atoms such as oxygen, sulphur, and nitrogen which make the ligand a better chelating ligand to coordinate strongly with different metal ions to form Schiff base metal complexes. Here, in this review, the synthesis of different types of Schiff bases customized from benzil and corresponding bidentate, tridentate, and tetradentate metal complexes has been summarized.

Abstract In this research work new heteroleptic Ni(II) and Pt(II) complexes have been synthesized by using 5-bromo-2-hydroxybenzaldehyde-4-phenylthiosemicarbazone as main ligand and triphenylphosphine and imidazole as auxiliary ligands. The ligand and complexes have been characterized by elemental analysis and spectroscopy. On the basis of results thiosemicarbazone is coordinated to metal ion as a dianionic tridentate ONS ligand and the coordination sphere is completed by the auxiliary ligand. Antibacterial activity of ligand and complexes was evaluated against B. subtilis and S. aureus and P. aeruginosa All complexes exhibit more inhibitory effect than the parent ligand and complexes containing imidazole have more activity than others.

Five rare earth complexeslanthanum(III),praseodymium(III),neodymium(III), samarium(III) and europium(III) have been synthesized from Schiff base ligand (N,N-bis (2-hydroxy-1-naphthylidene) acetylhydrazone). The complexes were characterized based on elemental analysis, molar conductance, ultraviolet, infrared, mass, thermogravimetric and powder X-ray diffraction studies. Infrared spectra suggest ligand act as a neutral tridentate ligand. The Schiff base ligand coordinating through the naphtholic oxygen without proton displacement, azomethine nitrogen atom and hydrazone carbonyl oxygen atoms of the ligand to the lanthanide ion. The conductivity and thermal decomposition studies indicate the presence of two coordinated nitrate ion acts as bidentate fashion. Powder X-ray diffraction studies reveal the neodymium complex has an orthorhombic system with different unit cell parameters. Europium, samarium, neodymium and praseodymium complexes exhibit the characteristic luminescence. Further, the in vitro antimicrobial activities of the metal complexes exhibited greater activity as compared with the ligand.

Coordination polymers (CPs) are synthesized using bridging organic ligands and metal ions, depending on the geometric coordination of the metal, the bridging ligands, and the donor atoms present in these ligands, various one-, two-, or three-dimensional polymeric structures can form. To investigate the effect of the position of the pyridine nitrogen atom in the tridentate NN'O Schiff base ligand on the type of coordination polymers, two copper complexes were prepared. The ligand HL2 was characterized using IR, NMR, and elemental analysis, while the complexes were analyzed and identified using IR, elemental analysis, and X-ray diffraction techniques. The structural data of the copper complexes indicated that changing the pyridine nitrogen from position 3 to position 4 in the Schiff base ligand altered the structure of the copper complex from two-dimensional to three-dimensional. Analysis of inter- and intramolecular interactions using the NCI program shows that the interactions in both molecules are of the hydrogen bonding, halogen bonding, CH…π, π…π stacking, metal…π, and lone-pair…π type.

The present work describes the studies on the coordination behaviour of 4[N-(benzalidene) amino]antipyrine semicarbazone (BAAPS) (I), 4[N-(furfural)amino]antipyrine semicarbazone (FFAAPS) (II) and 4[N-(cinnamalidene)amino]antipyrine semicarbazone (CAAPS) (III) in presence of dimethyl sulfoxide (DMSO) or diphenyl sulfoxide (DPSO) towards Th4+ and UO22+ salts. All the complexes were isolated in non-aqueous solvents like ethanol or acetone. The mixed ligand complexes have the general composition ThX4(L)DPSO (X = Cl, Br, I, NCS or NO3), Th(ClO4)4(L)2DPSO (L = BAAPS or CAAPS), UO2X2(L)DMSO (X = Br, I, NCS, NO3 or CH3COO) and UO2(ClO4)2(L)2DMSO (L=FFAAPS or CAAPS). The analytical data include elemental analyses, molecular weight determination, conductivity, spectral and thermal studies. XRD-powder diffraction of two representative thorium(IV) complexes have also been reported.In these complexes, the primary ligands behave as neutral tridentate (N, N, O) ligand, while the secondary ligand (DMSO or DPSO) acts as unidentate oxygen donor. Thorium(IV) displays coordination number 6,7,8 or 12, while uranium(VI) ion displays coordination number 8, 9 or 10 depending on the nature of anionic ligand.

In the present work, the authors describe the synthesis of some mixed ligand complexes of thorium(IV) derived from 4[N-(2''-hydroxy-1''-naphthalidene)amino]antipyrine semicarbazone (HNAAPS) or 4[N-(cinnamalidene)amino]antipyrinesemicarbazone (CAAPS) as primary ligand and diphenyl sulfoxide (DPSO) as secondary ligand with the general composition ThX4.n(L).DPSO (n = 1, X = Cl, Br, NCS or NO3; n = 2, X = I or ClO4, L = HNAAPS or CAAPS). All the compounds were characterized through elemental analysis, molar conductance, molecular weight, infrared data and thermogravimetric analysis. The infrared studies reveal that the semicarbazones behave as neutral tridentate (N,N,O) while DPSO coordinates through its oxygen atom. The nitrates are bicovalently bonded, while thiocyanates are N-coordinated in these compounds. In conclusion, the coordination number of the central metal ion displays coordination number 7, 8, 9 or 12 depending on the nature of the anionic ligands.