Spectroscopic studies of bridged binuclear complexes of Co(II), Ni(II), Cu(II) and Zn(II)

Binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of general composition [M₂L^1-2(μ-Cl)Cl₂] · nH₂O with the Schiff-base ligands (where L¹H and L²H are the potential pentadentate ligands derived by condensing 2,6-diformyl-4-methylphenol with 4-amino-3-antipyrine and 2-hydroxy-3-hydrazinoquinoxiline, respectively) have been synthesized and characterized. Analytical and spectral studies support the above formulation. ¹H-NMR and IR spectra of the complexes suggest they have an endogenous phenoxide bridge, with chloride as the exogenous bridge atom. The electronic spectra of all the complexes are well characterized by broad d–d and a high intensity charge-transfer transitions. The complexes are chloro-bridged as evidenced by two intense far-IR bands centered around 270–280 cm⁻¹. Magnetic susceptibility measurements show that complexes are antiferromagnetic in nature. The compounds show significant growth inhibitory activity against fungi Aspergillus niger and Candida albicans and moderate activity against bacteria Bacillus cirroflagellosus and Pseudomonas auresenosa.     

Synthesis,spectroscopic and electrochemical studies of copper(II) and cobalt(II) complexes of three unsymmetrical vic -dioximes ligands

Cobalt(II) and copper(II) complexes with three dioxime ligands cyclohexylamine-p-tolylglyoxime (L₁H₂), tert-butyl amine-p-tolylglioxime (L₂H₂) and sec-butylamine-p-tolylglyoxime (L₃H₂), have been prepared. The metal to ligand ratios of the complexes were found to be 1?:?2. The Cu(II) complexes of these ligands are proposed to be square planar; the Co(II) complexes are proposed to be octahedral with water molecules as axial ligands. Ligands and complexes are soluble in common solvents such as DMSO, DMF, CHCl₃ and C₂H₅OH. The ligands have been characterized by elemental analysis, IR, UV-VIS, ¹H?NMR, ¹³C?NMR and thermogravimetric analysis (TGA). The complexes were characterized by elemental analysis, IR, UV-VIS, magnetic susceptibility measurements, thermogravimetric analysis (TGA) and electrochemistry. Electrochemical properties of metal complexes show quasi-reversible one-electron redox processes. However, Co(L₁H)₂ and Cu(L₁H)₂ complexes show another oxidation peak in the positive region. This single irreversible oxidation peak is caused by the cyclic ring of the ligand. Data also revealed that the electron transfer rates of metal complexes with L₁H₂ are higher than the other complexes.     

Spectroscopic,crystal structure and thermal studies of Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with 5-amino-4-arylazo-3-methyl-1-phenylpyrazole (aryl=C6H5,o-C6H4COOH,o-C6H4OH)

5-Amino-4-arylazo-3-methyl-1-phenylpyrazole (aryl?=?C₆H₅,o-C₆H₄COOH,o-C₆H₄OH) and its complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) ions were synthesized. The complexes are in the ratio 1?:?1 and 1?:?2 (metal?:?ligand). Ligands and complexes were subjected to elemental analysis, IR, Raman, UV-Vis and ¹H-NMR spectroscopy. The mass spectra of the ligands were discussed. Thermal analysis and magnetic measurements were carried out for the prepared complexes. The X-ray single crystal structure of [Ni(L1)₂] was performed. The investigated pyrazole compounds coordinate as bidentate ligands through amino and azo nitrogens or tridentate through NNO. The molar conductance of the chelates is measured and reflected the non-electrolytic nature of the prepared complexes.     

Synthesis and spectral studies of copper(II), nickel(II), cobalt(II) and vanadyl(II) complexes of tridentate Schiff bases of 1,2,3,5,6,7,8,8a-octahydro-3-oxo-N,1-diphenyl-5-(phenylmethylene)-2-naphthalenecarboxamide

Summary Metal(II) chelates of Schiff bases derived from the condensation of 1,2,3,5,6,7,8,8a-octahydro-3-oxo-N,1-diphenyl-5-(phenylmethylene)-2-naphthalenecarboxamide with o-aminophenol (KAAP), o-aminothiophenol (KAAT) or o-aminobenzoic acid (KAAB) have been prepared and characterized. The complexes are of the type [M(N₂X)]₂ for M = Cu^II and M(NX)₂·nH₂O for M = Ni^II, Co^II and VO^II (X = phenolic oxygen, thiophenolic sulphur or carboxylic oxygen; n = 0 or 2). Conductivity data indicate that the complexes are non-ionic. The Schiff bases behave as dibasic tridentate ligands in their copper(II) complexes and as monobasic bidentate ligands in their nickel(II), cobalt(II) and vanadyl(II) complexes. The subnormal magnetic moments of the copper(II) complexes are ascribed to an antiferromagnetic exchange interaction arising from dimerization. Nickel(II) and cobalt(II) complexes are trans octahedral whereas vanadyl(II) complexes are square pyramidal     

Spectrothermal studies of 1,10-phenanthroline complexes of Co(II), NI(II), Cu(II) and Cd(II) orotates

The 1,10-phenanthroline (phen) complexes of Co(II), Ni(II), Cu(II) and Cd(II) orotates were synthesized and characterized by elemental analysis, magnetic susceptibility, spectral methods (UV-vis and FTIR) and thermal analysis techniques (TG, DTG and DTA). The Co(II), Ni(II), Cu(II) and Cd(II) ions in diaquabis(1,10-phenanthroline)metal(II) diorotate octahedral complexes [M(H₂O)₂(phen)₂](H₂Or)₂·nH₂O (M=Co(II), n=2.25; Ni(II), n=3; Cu(II) and Cd(II), n=2) are coordinated by two aqua ligands and two moles of phen molecules as chelating ligands through their two nitrogen atoms. The monoanionic orotate behaves as a counter ion in the complexes. On the basis of the first DTG_max, the thermal stability of the hydrated complexes follows the order: Cd(II), 68°C 68°C     

Synthesis of copper(II) and nickel(II) triazacycloalkane complexes

Summary Copper(II) and nickel(II) complexes of triazacycloalkanes (pqr-cy), with p, q, r = 2–6, have been prepared and characterized by means of electronic and i.r. spectroscopy, and by magnetic measurements. With nickel(II) mononuclear octahedral complexes [Ni(pgr-cy)₂](CI0₄)₂ are formed, but for copper(II) mononuclear octahedral complexes were obtained only for 222-cy and 223-cy. The other ligands gave copper(II) complexes of the type [Cu(pgr-cy)CI]CIO₄, [Cu(pgr-cy)OH]ClO₄, Or [Cu(pgr-cy)CI_1/2OH_1/2]ClO₄. The hydroxy complexes have low magnetic moments and binuclear hydroxy bridged structures are proposed.Ligand names: e.g. p = q = r = 2 is 1,4,7-triazacvclononane     

The synthesis of two new isonitrosoacetophenone derivatives and investigation of their Ni(II), Co(II), Cu(II), and Zr(IV) complexes

In the present study, two new ligands, 4-chlorobenzal-azino-isonitrosoacetophenone (L₁), 4-methylbenzal-azino-isonitrosoacetophenone (L₂) and their metal complexes were synthesized using acetophenone as a starting material. The coloured complexes were prepared by the addition of chloride salts of Ni(II), Co(II), Cu(II) and Zr(IV) ions to a solution of ligands. In conclusion, the structures of the obtained ligands and their complexes were characterized by FT-IR, and ¹H NMR spectra, AAS (atomic absorption spectrum) analysis, magnetic susceptibilities as well as elemental analysis.     

Synthesis,Spectral and Structural Characterization of the First Bis-2-Pyridylethanol Complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) Saccharinates: Crystal Structures of Diaquabis(2-Pyridylethanol)Iron(II) and Copper(II) Saccharinates

The first 2-pyridylethanol (pyet) complexes of manganese(II), iron(II), cobalt(II), nickel(II), copper(II) and zinc(II) saccharinates, were synthesized and characterized by elemental analyses, magnetic measurements, UV-Vis, and IR spectroscopic techniques. Crystal and molecular structures of the iron(II) and copper(II) complexes were determined by single crystal X-ray diffractometry. The experimental data showed that all the complexes are mononuclear with a general formula [M(H₂O)₂(pyet)₂](sac)₂, where sac is the saccharinate anion. All the metal ions are octahedrally coordinated by two aqua and two pyet ligands. The pyet ligand acts as a bidentate ligand through its amine nitrogen and hydroxyl oxygen atoms forming a six-membered chelate ring, while the sac ions remain outside the coordination sphere. All the complexes are isomorphous with a monoclinic space group P2₁/n and Z = 2.     

Sulfobridged Polynuclear Complexes of Platinum(II) and Palladium(II)

When the platinum(II) and palladium(II) salts interact with ligands such as cystamine-(mercamine) HSCH₂CH₂NH₂ and 2-mercaptoethanol HSCH₂CH₂OH under certain conditions, polynuclear complexes of the compositions are obtained: [Pt₆(SCH₂CH₂NH₂)₈]Cl₄. 5H₂O and [Pd₆(SCH₂CH₂OH)₈]Cl₄. In a comparative study of the IR and X-ray spectra of synthesized complexes and ligands, as well as the results of X-ray diffraction studies, it was established that sulfur atoms of 2-mercaptoethanol occupy a bridge position with a mixed coordination of ligands in the palladium complex. In the platinum(II) complex bidentate coordination of ligands is realized through sulfur and nitrogen atoms.     

Heteronuclear complexes of oxorhenium(V) with Fe(III), Co(II), Ni(II), Cu(II), Cd(II) and UO2(VI) and their biological activities

Heteronuclear complexes containing oxorhenium(V), with Fe(III), Co(II), Ni(II), Cu(II), Cd(II) and UO₂(VI) ions were prepared by the reaction of the complex ligands [ReO(HL¹)(PPh₃)(OH₂)Cl]Cl (a) and/or [ReO(H₂L²)(PPh₃)(OH₂)Cl]Cl (b), where H₂L¹?=?1-(2-hydroxyphenyl)butane-1,3-dione-3-(5,6-diphenyl-1,2,4-triazine-3-ylhydrazone) and H₃L²?=?1-(2-hydroxyphenyl)butane-1,3-dione-3-(1H-benzimidazol-2-ylhydrazone), with transition and actinide salts. Heterodinuclear complexes of ReO(V) with Fe(III), Co(II), Ni(II), Cu(II) and Cd(II) were obtained using a 1?:?1 mole ratio of the complex ligand and the metal salt. Heterotrinuclear complexes were obtained containing ReO(V) with UO₂(VI) and Cu(II) using 2?:?1 mole ratios of the complex ligand and the metal salts. The complex ligands a and b coordinate with the heterometal ion via a nitrogen of the heterocyclic ring and the nitrogen atom of the C=N⁷ group. All transition metal cations in the heteronuclear complexes have octahedral configurations, while UO₂(VI)?complexes have distorted dodecahedral geometry. The structures of the complexes were elucidated by IR, ESR, electronic and ¹H NMR spectra, magnetic moments, conductance and TG-DSC measurements. The antifungal activities of the complex ligands and their heteronuclear complexes towards Alternaria alternata and Aspergillus niger showed comparable behavior with some well-known antibiotics.     

Estimation of coordination bond energies of NH3, H2O and Et2NH ligands in the Ni(II) and Cu(II) complexes

Tridentate ligands 2-hydroxyphenylsalicylaldimine (SAPH₂), 2-hydroxyphenyl-2-hydroxy-1-naphtalaldimine (NAPH₂) and Ni(II) complexes with multidentate ligand Bis-N·N′-(salicylidene)-1,3-propanediamine (LH₂) as well as mononuclear complex of Cu(II) were prepared using the same multidentate ligand. Diethylamine (Et₂NH), NH₃ and H₂O monodentate ligands were bound to these complexes coordinatively. The heat absorbed at the temperatures where these ligands thermally dissociated from the complexes were measured using the TG and DSC methods. It is assumed that the states both of the complexes with and without the monodentate ligands are solid and coordination bond energy for the monodentate ligand is calculated. It is seen that these calculated coordination bond energies are comparable with hydrogen bond energies.     

Synthesis of Substituted 4,4′-Oxy-bis(aminophenylglyoximes) and Their Polymeric Metal Complexes with Cu(II), Ni(II), and Co(II) Salts

4,4′-Bis(chloroacetyl)diphenyl ether (HL) was synthesized from chloroacetyl chloride and diphenyl ether in the presence of AlCl₃ as catalyst by Friedel-Crafts reaction. Subsequently, its keto oxime (H₂L) and glyoxime (H₄L) derivatives were also prepared. Then, five new substituted 4,4′-oxy-bis(aminophenyl-glyoximes) (H₄L_1–5) were synthesized from 4,4′-oxy-bis(chlorophenylglyoxime) and the corresponding amines. The Ni(II), Cu(II), and Co(II) complexes of these ligands were prepared. The structures of these ligands and their complexes were identified by FT-IR, ¹H NMR, and ICP-AES spectral data, elemental analyses, and magnetic measurements.     

Synthesis,characterization and anticancer studies of bis-(N-methyl-1-phenyldithiocarbamato) Cu(II), Zn(II), and Pt(II) complexes: single crystal X-ray structure of the copper complex

Abstract

Cu(II), Pt(II), and Zn(II) complexes of N-methyl-1-phenyldithiocarbamate were synthesized and characterized by FTIR, NMR, UV-visible spectroscopy and elemental analysis. The complexes were formulated as [Cu(L)₂], [Zn(L)₂] and [Pt(L)₂] (where L?=?N-methyl-1-phenyldithio­carbamate) in which two molecules of the ligands coordinate to the metal ions in a bidentate chelating fashion. This is confirmed by elemental analysis and the presence of strong single bands at 952, 951, and 955?cm^?1 for Cu(II), Pt(II), and Zn(II) complexes, respectively, in the FTIR spectra. The electronic spectra of Pt(II) and Cu(II) complexes are consistent with four-coordinate square planar geometry. Single crystal X-ray of [Cu(N-mpDTC)₂] confirmed square planar structural arrangement (CuS₄) in which the ligands are asymmetrically bonded to the Cu(II) ion building a centrosymmetric monomer entity. The S-Cu-S bite angle is 77.95° (3) whereas the intramolecular N–C bond length is 1.318 Å and trans S1¹-Cu-S1?=?S2¹-Cu-S2 is 180°, which are consistent with reported copper thiolates in square planar environment. In vitro antiproliferative activity of the complexes against three human cancer cell lines showed that the zinc complex has better activity compared to Cu and Pt complexes, with IC₅₀ values of 14.28, 22.74 and 20.10?μM against TK10, UACC62, and MC7 cell lines, respectively.     

Varieties in structures of Co(II), Ni(II) and Cu(II) coordination compounds based on dimethyl pyridin-2-ylcarbamoylphosphoramidate

A series of new 3d metal complexes based on dimethyl pyridin-2-ylcarbamoylphosphoramidate (HL) was synthesized. The compounds with general formula M(HL)₂Cl₂·nH₂O and M(L)₂·nH₂O (M=Co²⁺, Cu²⁺, Ni²⁺) were characterized by means of single-crystal X-ray analysis and IR spectroscopy. The organic ligands in all complexes are coordinated via oxygen atom of the carbonyl group and nitrogen atom of the heterocycle. The coordination environment of the central atoms is a distorted octahedron. The axial positions in the Co(II) and Ni(II) complexes with deprotonated ligands are occupied by water molecules. The Co(II) and Cu(II) complexes with phosphoryl ligands in a neutral form have different ligands in the axial positions: in the Co(II) complex, the positions are occupied by two water molecules, whereas in the Cu(II) complex, the positions are occupied by two chlorine anions. The structure of HL was experimentally and theoretically obtained by utilizing single-crystal X-ray analysis and DFT calculations. The computationally optimized geometric parameters for HL show a good agreement with the experimental results.     

Synthesis,Characterization, DNA Binding Properties,and Antioxidant Activity of Novel Copper(II) and Zinc(II) Complexes with Bis(pyrrol‐2‐yl‐methylamine) Ligands

Three novel ligands H₄Lⁿ (n = 1–3) and their copper(II) and zinc(II) complexes were prepared and characterized on the basis of elemental analyses, molar conductivity, ¹H NMR, UV/Vis, and IR spectroscopy as well as mass spectrometry. DNA binding properties of the ligands and their complexes were investigated by absorption spectroscopy, ethidium bromide displacement experiments, and viscosity measurements. The experimental results indicate that the new ligands and their complexes can bind to DNA and the binding affinities of the complexes are higher than those of the ligands. In addition, the antioxidant activity of the ligands and complexes was determined by superoxide and hydroxyl radical scavenging methods in vitro, indicating that the complexes exhibit more effective antioxidant activity than the ligands alone.     

Metal complexes with pyridone-based radicals: Preparation and properties of a dinuclear paddle-wheel copper(II) complex and a mononuclear palladium(II) complex

We prepared and characterized dinuclear copper(II) and mononuclear palladium(II) complexes coordinated with a pyridine-based open-shell ligand, 5-(4′,4′,5′,5′-tetramethylimidazoline-3′-oxide-1′-oxyl)-2(1H)-pyridone (=HL). In the copper(II) dinuclear complex [Cu₂(L)₄(DMF)₂] (1), four deprotonated ligands are coordinated as bridging ligands to form a paddle-wheel type unit. In the palladium(II) complex trans-[PdCl₂(HL)₂] (2), two HL ligands in the neutral hydroxypyridine form are coordinated to the trans positions of the metal ion via the nitrogen atoms. The hydroxyl groups of the ligands are hydrogen-bonded to the chlorine atoms of neighboring molecules, thereby creating a hydrogen-bonded double-chain molecular arrangement. Magnetic susceptibilities of these complexes were measured and analyzed. The small intramolecular antiferromagnetic interaction in the latter complex may originate from superexchange through the diamagnetic metal center.     

Diazabutadiene cobalt(II) complexes

Summary Studies on the chelates of cobalt(II) with the bidentate ligands 1,4-diphenyl(2,3-dimethyl-1,4-diazabutadiene) (PMB) and 1,4-di(p-methoxyphenyl)-2,3-dimethyl-1,4-diazabutadiene (MPMB) have been carried out. On the basis of elemental analyses, the complexes are [Co(PMB)Cl₂], [Co(PMB)₂(C1O₄)₂], [Co(MPMB)Cl₂] and [Co(MPMB)₂(ClO₄)₂].Both ligands are bidentatevia nitrogen atoms in all the complexes. The magnetic susceptibility and i.r. and u.v.-visible spectra are reported and discussed. The chloro-compounds involving two chlorine ligands and, in the perchlorate compounds, the ClO ₄ ^– groups are bound to the cobalt(II) centre.     

Coordination of uridine and adenosine to Pd(II) and Pt(II) complexes

Uridine (and thymidine) undergo proton loss at N3 and coordinate as anions to displace all water molecules from dienPd(OH₂)²⁺, dienPt(OH₂)²⁺, enPd(OH₂)₂²⁺ and enPt(OH₂)₂²⁺ to form fully substituted complexes in neutral solutions. Though favored at equilibrium at low pH, the reactions of the ligands with the Pt(II) complexes proceed slowly because of the sluggishness of Pt(II) substitutions and the small fractions of ligands with pK_a from 9.3 to 9.8 in the anionic basic form. Both dienPd(OH₂)²⁺ and dienPt(OH₂)²⁺ form two mononuclear complexes with the metal ion at N1 and N7 of adenosine and a binuclear complex with metal ions at both sites. In the mononuclear complexes dienPd(II) favors N1 over N7 coordination by 5 to 1 while dienPt(II) is nearly equally distributed between the two sites when reacting with a neutral adenosine molecule.     

Synthesis and characterization of zinc(II), copper(II) and cadmium(II) coordination polymers with tetrachloroterephthalate-based ligands

Three complexes, namely Zn(BDC-Cl₄)(py)₃ (1), Cu(BDC-Cl₄)(py)₃ (2) and Cd(BDC-Cl₄)(py)₃ (3) (BDC-Cl₄ = 2,3,5,6-tetrachloro-1,4-benzenedicarboxylate, py = pyridine) have been synthesized. Complexes (1) and (2) have been obtained using solvothermal methods. Both have a five-coordinate geometry with two bridging monodentate tetrachloroterephthalate ligands and three pyridine ligands coordinated to the Zn(II) or Cu(II) atom. The tetrachloroterephthalate ligands bridge the adjacent Zn(II) or Cu(II) centers, giving zigzag chains. Complex (3) has also been crystallized, each Cd(II) atom is six-coordinated to three carboxylate oxygen atoms and three pyridyl nitrogen atoms. Two types of tetrachloroterephthalate ligand, featuring monodentate and bidentate carboxylates, connect the Cd(II) centers to form zigzag chains. All three complexes have been subjected to thermogravimetric analysis.     

Synthesis,characterization, and antimicrobial activities of nickel(II) and copper(II) Schiff-base complexes

Ni(II) and Cu(II) metal complexes of simple unsymmetrical Schiff-base ligands derived from salicylaldehyde/5-methylsalicylaldehyde and ethylenediamine or diaminomaleonitrile (DMN) were synthesized. The ligands and their complexes were characterized by elemental analysis, ¹H NMR, FT IR, and mass spectroscopy. The electronic spectra of the complexes show d–d transitions in the region at 450–600 nm. Electrochemical studies of the complexes reveal that all mononuclear complexes show a one-electron quasi-reversible reduction wave in the cathodic region. ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry, with nuclear hyperfine spin 3/2. The copper(II) complexes show a normal room temperature magnetic moment value μ _eff = 1.70–1.74 BM which is close to the spin only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts were also carried out. The in vitro antimicrobial activity of the investigated compounds was tested against human pathogenic bacterias such as Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumonia, Pseudomonas aeruginosa and Escherichia coli. The antifungal activity was tested against Candida albicans. Generally, the metal complexes have higher antimicrobial activity than the free ligands.