Structural, spectral and antimicrobial studies of copper(II) complexes of 2-benzoylpyridine N(4)-cyclohexyl thiosemicarbazone

Six new copper(II) complexes of 2-benzoylpyridine N(4)-cyclohexyl thiosemicarbazone (HL) have been synthesized and characterized by different physicochemical techniques like molar conductivity measurements, magnetic studies and electronic, infrared and EPR spectral studies. Five of the complexes have been found to possess the stoichiometry [CuLX], where X = Cl (1), Br (2), NO₃ (3), NCS (4), N₃ (5). The complex prepared from copper sulfate has the composition [Cu₂L₂SO₄] · (H₂O)₂ (6). In all the complexes the deprotonated ligand, L and the anion were found to be coordinated to the Cu(II) ion. The terdentate nature of the ligand is evident from the IR spectra. The metal ligand bonding parameters evaluated from the EPR spectra indicate strong in-plane σ and in-plane π bonding. The magnetic and spectroscopic data indicate a square planar geometry for complexes 1, 3, 4 and 5, while the complexes 2 and 6 are assigned a square pyramidal geometry. Crystal structure of the complex [CuLCl] reveals two molecules per asymmetric unit of a monoclinic lattice, with space group symmetry P2₁/n. The complexes [ CuLBr ₂] (2) and [CuLNCS] (4) crystallized into triclinic lattices with space group . Compound 2 exists as a thiolate bridged copper(II) dimer. The antimicrobial activity of the ligand and the copper complexes were tested against five types of bacteria isolated from clinical samples. The complexes were found to be active against Bacillus sp., Vibrio cholera O1, Staphylococcus aurus and Salmonella paratyphi.     

Synthesis, structure and properties of delocalized transition metal chelates: Diazoketiminato chelates of Co(III) and Pt(II)

The reactions of HL 1 [where HL is 1N-(2-pyridyl-2-methyl)-2-arylazoaniline and is formulated as ArN = NC₆H₄N(H)(CH₂C₅H₄N); Ar = C₆H₅ (for HL¹) or p-MeC₆H₄ (for HL²) or p-ClC₆H₄ (for HL³)] with K₂PtCl₄ and Co(ClO₄)₃ · 6H₂O afforded the (L)PtCl and [(L)₂Co]ClO₄ complexes, respectively. The HL ligands bind the platinum(II) and cobalt(III) centres in a tridentate (N,N,N) fashion, forming new diazoketiminato chelates upon dissociating the amino proton. The X-ray structures of (L³)PtCl and [(L³)₂Co]ClO₄ were determined. Redox properties of the new complexes have been examined.     

Spectroscopic evaluation of Co(II), Ni(II) and Cu(II) complexes derived from thiosemicarbazone and semicarbazone

Co(II), Ni(II) and Cu(II) complexes were synthesized with thiosemicarbazone (L(1)) and semicarbazone (L(2)) derived from 2-acetyl furan. These complexes were characterized by elemental analysis, molar conductance, magnetic moment, mass, IR, electronic and EPR spectral studies. The molar conductance measurement of the complexes in DMSO corresponds to non-electrolytic nature. All the complexes are of high-spin type. On the basis of different spectral studies six coordinated geometry may be assigned for all the complexes except Co(L)(2)(SO(4)) and Cu(L)(2)(SO(4)) [where L=L(1) and L(2)] which are of five coordinated square pyramidal geometry.     

Synthesis and physicochemical studies on Co(III) complexes

Complexes of Co(III) with 2-hydroxyacetophenone-thiosemicarbazone, 2-hydroxy-3-methylacetophenonethiosemicarbazone and 2-hydroxy-4-methyl-acetophenonethiosemicarbazone, and the addition complexes of 2-hydroxy-acetophenone thiosemicarbazone with ammonia, pyridine, aniline,o-toluidine,m-toluidine andp-toluidine have been synthesized and characterized on the basis of their conductivities, electronic and infrared spectral data. All complexes are low-spin octahedral in nature. Various parameters have been obtained using ligand field theory.     

氮氧杂链型配体合成与Cu(Ⅱ)和Zn(Ⅱ)配位性质研究

合成了4种氮氧杂链型配体N,N'-二-(2-羟乙基)-乙二胺(L¹)、N-(2-羟基苄基)-丙醇胺(HL²)、N-(2-羟乙基)-N'-(2-羟基苄基)-乙二胺(HL³)和N-(2-羟乙基)-二乙三胺-(L⁴),通过元素分析、IR和¹H NMR等手段表征了其结构,用pH电位滴定法在25℃、I=0.10(KNO₃)条件下,测定了L¹和HL²与Cu(Ⅱ)离子以及HL³和L⁴与Zn(Ⅱ)离子配位平衡常数.结果表明:L¹和HL²与Cu(Ⅱ)离子配位时,均可生成四配位配合物,其中第三配位点醇羟基配位较强,其质子离解常数pK_a1分别为7.28和7.32;第四配位点是第2个醇羟基或1个水分子配位,其pK_a2分别为9.33和9.04;HL³和L⁴与Zn(Ⅱ)均可生成五配位配合物,第四配位点均为醇羟基,其离解常数pK_a1分别为7.76和7.96,第五配位点均为H₂O,其pK_a2分别为9.47和9.57.从上述热力学结果可见,配合物在中性pH值范围能生成亲核试剂Cu(Ⅱ)…^-OR或Zn(Ⅱ)…^-OR,而且均具备双重催化酯类底物水解的条件.     

Structural and spectral characterization of two 1-phenyl-1,2-propanedione bis{N(4)-alkylthiosemicarbazones}

1-phenyl-1,2-propanedione bis{N(4)-methyl- and {N(4)-ethylthiosemicarbazone}, H₂Pm4M and H₂Pm4E, respectively, have been prepared, studied spectroscopically (¹H NMR, ultraviolet and infrared) and their crystal structures solved. Intermoiety hydrogen bonding does not occur in H₂Pm4M and H₂Pm4E, in contrast to the analogous bis{N(4)-thiosemicarbazones} prepared from 1-phenylglyoxal. The two thiosemicarbazone moieties are on the opposite side of the carbon–carbon backbone, but the N(4)Hs intramolecularly hydrogen bond to the imine nitrogen for each moiety.     

Spectral studies on Co(II), Ni(II) and Cu(II) complexes with thiosemicarbazone (L1) and semicarbazone (L2) derived from 2-acetyl furan

Co(II), Ni(II) and Cu(II) complexes are synthesized with thiosemicarbazone (L1) and semicarbazone (L2) derived from 2-acetyl furan. These complexes are characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, mass, IR, electronic and EPR spectral studies. The molar conductance measurements of the complexes in DMSO correspond to non-electrolytic nature except Ni(L)2(NO3)2, which is 1:2 electrolyte. All the complexes are of high-spin type. On the basis of spectral studies an octahedral geometry may be assigned for Co(II) and Ni(II) complexes except nitrato complexes of Ni(II) which is of tetrahedral geometry, whereas tetragonal geometry for Cu(II) complexes.     

Cyano-bridged bimetallic complexes of copper(II) with tetracyanonickelate(II). Crystal structure of [Cu(dpt)Ni(CN)4]

Five new complexes of composition [Cu(dpt)Ni(CN)₄] (1) (dpt=dipropylenetriamine), [Cu(dien)Ni(CN)₄]·2H₂O (2) (dien=diethylenetriamine), [Cu(N,N′-dimeen)Ni(CN)₄]·H₂O (3) (N,N′-dimeen=N,N′-dimethylethylenediamine), [Cu(N,N-dimeen)Ni(CN)₄]·H₂O (4) (N,N-dimeen=N,N-dimethylethylenediamine) and [Cu(trimeen)Ni(CN)₄] (5) (trimeen=N,N,N′-trimethylethylenediamine) have been obtained by the reactions of the mixture of Cu(ClO₄)₂·6H₂O, appropriate amine and K₂[Ni(CN)₄] in water and have been characterized by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dpt)Ni(CN)₄] (1) has been determined by single-crystal X-ray analysis. The structure of 1 consists of a one-dimensional polymeric chain ---Cu(dpt)---NC---Ni(CN)₂---CN---Cu(dpt)--- in which the Cu(II) and Ni(II) atoms are linked by CN groups. The nickel atom is four coordinate with four cyanide-carbon atoms (two cyano groups are terminal and two cyano groups (in cis fashion) are bridged) in a square-planar arrangement and the copper atom is five coordinate with two cyanide-nitrogen and three dpt-nitrogen atoms, in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibility (2–300 K) was measured for compound 1. The magnetic investigation showed the presence of a very weak antiferromagnetic interaction (J=−0.16 cm⁻¹) between the copper atoms within each chain through the diamagnetic Ni(CN)₄ ²⁻ ions.     

Synthesis and crystal structures of two new Cd(II) complexes with 3-(2-pyridy)pyrazole-based ligand: influence of anions

Two new Cd(II) complexes with a 3-(2-pyridyl)pyrazole-based ligand, [Cd(L)₂(SCN)₂] (1) and {[Cd(L)₂N₃](ClO₄)}_n (2) (L=3-(2-pyridyl)pyrazol-1-ylmethylbenzene) were synthesized and structurally characterized by elemental analyses, IR and single crystal X-ray diffraction analysis. Complex 1 crystallizes in the monoclinic system, space group C2/c, with a=14.833(3), b=13.790(3), c=15.970(3) Å, β=110.89(3)° and Z=4, while 2 crystallizes in the monoclinic system, space group P2₁/c, with a=13.622(4), b=23.286(7), c=10.547(3) Å, β=111.084(6)° and Z=4. In the two complexes, the Cd(II) centers are coordinated by six nitrogen atoms, in which four from two distinct L ligands and two from thiocyanato (1) or azido (2) anions. Complex 1 has a mononuclear structure, whereas 2 has a 1D chain structure bridged by azido anions. In 2, the azido adopts a μ-1,3-trans coordination mode, which is not common in the azide Cd(II) complexes. In addition, in the structure of 2, the 1D chains were further assembled into a quasi-3D supramolecular network by the C–HO hydrogen-bonding interactions. The structural difference of the two complexes is attributable to the different anions, which have different coordination natures.     

Photoredox behaviour of trans and cis Co (III)-diisothiocyanatotetram(m)ine complexes

The trans and cis isomers of Co(NCS)₂(NH₃)₄⁺ and Co(NCS)₂(en)₂⁺ were prepared and characterized. Single-crystal X-ray diffraction showed that the first named was the trans isomer and established that the thiocyanates are N bonded. Photoredox quantum yields of the Co²⁺ ion on room temperature irradiation at 360 nm were found to be 0.065±0.001, 0.0082±0.001, 0.0088±0.0007 and 0.0040±0.0010 respectively. Other products measured were the thiocyanate ion and ammonia, but the relationships of these yields to Co²⁺ were not as expected for simple oxidation of thiocyanate and reduction of Co(III). On irradation in the presence of thiocyanate, a significant increase in yields occurs and this can be modelled in terms of scavenging of the thiocyanate radical from an initial caged radical pair giving picosecond estimates for the lifetime of this species of the order of tens of picoseconds, or in terms of photolysis of a thiocyanate/complex ion pair giving formation constant of 0.25±0.17, 0.12±0.04, 0.11±0.06 and 0.06±0.04 for the complexes in the sequence above. In all but the last instance these are in excellent agreement with the values estimated by fitting the thiocynate induced changes in the UV-visible spectra of the complexes, 0.34±0.25, 0.14±0.07, 0.09±0.07 and 0.60±0.07 respectively. Laser flash photolysis studies on the nanosecond and picosecond time-scale failed to reveal any direct spectroscopic evidence for a radical pair species, but the absorbance of (NCS)₂^-√ was seen in all four systems. The effects of added electrolytes and of viscosity on the formation and decay of this intermediate were investigated and are reported in detail.     

Photodynamic action of bis(tertiary arsine (diars)) metal(III) complexes trans-[M(diars)2X2] (X = Cl, Br, I); M = Co, Cr, Rh: Optical and EPR spin-trapping studies

Photodynamic properties of series of metal complexes having the general formula [M(diars)₂X₂]ClO₄ or BF₄ where M = Co³⁺, Cr³⁺, Rh³⁺; X = Cl, Br, I, diars = o-phenylene bis(dimethylarsine) are studied. Photogeneration of singlet oxygen is monitored by both optical and EPR methods. In comparison with rose bengal ((¹O₂) for RB = 0.76), singlet oxygen generating efficiencies of these complexes are determined. Rate of N,N-dimethyl-4-nitrosoaniline (RNO) bleaching is found to be retarded by specific ¹O₂ quencher NaN₃, confirming the involvement of ¹O₂ as an active intermediate. Photolysis of these complexes in the presence of spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) generates 12-line EPR spectra, characteristic of O₂⁻ adduct. Photogeneration of O₂⁻ is also monitored by optical spectroscopy using superoxide dismutase (SOD) inhibitable cytochrome c reduction assay. The results indicate that the [Co(diars)₂Br₂]ClO₄ complex possesses high ability to generate reactive oxygen species (ROS). Both Type I and II paths are involved in the photosensitisation of the metal complexes. The antimicrobial activity of the complexes against selected bacteria is estimated. The relationship between the enzymatic production of ROS and antimicrobial activity of the complexes is examined and a good correlation between two factors is found. The [CoBr₂(diars)₂]ClO₄ complex investigated in this study effect photo cleavage of the plasmid DNA (pUC18).     

Synthesis and magnetism of the first tetranuclear copper(II)–iron(III) complexes of macrocyclic oxamides

Four novel tetranuclear macrocyclic complexes of the formula [(CuLⁱ)₃Fe](ClO₄)₃·3H₂O (i=1–4, Lⁱ are the dianions of the [14]N₄ and [15]N₄ macrocyclic oxamides, namely 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene] have been prepared and characterized. These complexes are the first examples of oxamido-bridged Cu(II)–Fe(III) heterometallic species. Cryomagnetic studies on [(CuL¹)₃Fe](ClO₄)₃·3H₂O (1) and [(CuL³)₃Fe](ClO₄)₃·3H₂O (3) (77–300 K) revealed that the Cu(II) and Fe(III) ions interact antiferromagnetically through the oxamido bridge, with the exchange integral J=−30.8 cm⁻¹ for 1 and J=−28.7 cm⁻¹ for 3 based on . The interaction parameters have been compared with that of the related [Cu₃Mn] compound.     

Synthesis and characterization of two tris-chelate complexes of cobalt(III) with 3,5-dimethyl-1-(N-methyl/ethyl)thiocarbamylpyrazole (HL1, HL2) — biologically important bidentate ligands with one ambidentate donor site

Cobalt(III) complexes, of two potentially pyrazole-derived bidentate ligands (with one ambidentate donor site), 3,5-dimethyl-1-(N-methyl/ethyl)thiocarbamylpyrazole (HL₁ for N-methyl, HL₂ for N-ethyl) have been synthesized and characterized by elemental analyses, IR, UV–Vis and ¹H NMR spectral studies. The structure of Co(L₂)₃ has been determined by single-crystal X-ray diffraction studies. The complex (triclinic, space group P ) has a distorted octahedral structure with the ambidentate ligands coordinated to the Co(III) ion as uninegative bidentate chelating agents via the pyrazole ring nitrogen (tertiary) and the thiocarbamyl iminyl nitrogen atoms. The distortion from the regular octahedral geometry is ascribed to the stereochemical limitations imposed by the planar bidentate ligands.     

Ru- and Fe-based N,N′-bis(2-pyridylmethyl)-N-methyl-(1S,2S)-1,2-cyclohexanediamine complexes immobilised on mesoporous MCM-41: Synthesis, characterization and catalytic applications

Protected mesoporous MCM-41 phases were synthesized by grafting of the ligand, (1S,2S)-N,N′-bis-pyridin-2-ylmethyl-cyclohexane-1,2-diamine (L₂Me), through the reactive 3-chloropropyltrimethoxysilane (3-CPTMS) group and designated as L₂Me-MCM-41. Subsequently, RuCl₃ and Fe(BF₄)₂ or Fe(CF₃SO₃)₂ were added to the heterogenized L₂Me-MCM-41 for complexation and designated as M-L₂Me-MCM-41 (M = Ru and Fe). All samples were characterized in detail using XRD, N₂ sorption isotherm, FT-IR, TGA-DTA, XPS, UV–vis, solid state ¹³C NMR, EPR and elemental analysis, etc. The XRD and sorption measurements of the catalyst confirmed the structural integrity of the mesoporous hosts and the spectroscopic characterization techniques proved the successful anchoring of the metal complexes over the modified mesoporous support. The screening of catalyst M-L₂Me-MCM-41 was done for the oxidation reaction of thioanisole (methyl phenyl sulphide) using H₂O₂ as an oxidant. The Ru-L₂Me-MCM-41 and Fe-L₂Me-MCM-41 catalysts show higher activities and turnover numbers and exhibit enantiomeric excess comparable to the homogeneous catalysts, Ru-L₂(Me)₂ and Fe-L₂(Me)₂. Furthermore, Fe-L₂Me-MCM-41 and Fe-L₂(Me)₂ were also found active in the epoxidation of styrene. These results indicate that metal complexes are confined into the pore of the material which play a major role in the reaction.     

Syntheses and X-ray crystal structures of [Co(η-CO3)(NH3)4](NO3)·0.5H2O and [(NH3)3Co(μ-OH)2(μ-CO3)Co(NH3)3][NO3]2·H2O

[Co(η²-CO₃)(NH₃)₄](NO₃)·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O were prepared by prolonged aerial oxidation of a solution of Co(NO₃)₂·6H₂O and ammonium carbonate in aqueous ammonia. The formation of these side products highlights the richness of the chemistry of these systems and the possibility of by products if methods are not strictly adhered to. The X-ray crystal structures of [Co(η²-CO₃)(NH₃)₄][NO₃]·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O reveal a monomeric octahedral cobalt center with η²-bound CO₃²⁻ in the former, while the latter consists of a dimeric array where the two cobalt centers are bridged by two OH⁻ and one μ₂-CO₃²⁻ groups with three terminal NH₃ ligands for each Co center. In both complexes extensive hydrogen bonding interactions are evident.     

Synthesis and characterization of [Cp*Fe-dicyclopenta(a,f)naphthalene-FeCp*] and [Cp*Fe-dicyclopenta(a,f)naphthalene-FeCp*] BF4

[Cp*Fe-dicyclopenta(a,f)naphthalene-FeCp*]ⁿ⁺ (Cp*=pentamethylciclopentadiene, n=0, 1), respectively named complexes V and VI, were synthesized and characterized. The X-ray structure has been solved and ¹H-, ¹³C-NMR and elemental analysis were performed for the n=0 complex. Cyclic voltammetry showed a potential difference of 360 mV within the two redox peaks. An absorption band at 850 nm was assigned to an intervalence band. The Mössbauer investigations show a uniform Fe²⁺ environment for the neutral compound and two sites, assigned to Fe²⁺ and Fe³⁺ for the monoxidized compound. The information gathered by all the previously mentioned techniques indicates that the studied binuclear compound belongs to the mixed valence class II using Robin and Day classification.     

Preparation of palladium complexes of 1,3-di(2-pyridyl)propane derivatives and their use in norbornene polymerization

A variety of neutral palladium(II) complexes [Pd(L–L)Cl₂] containing 1,3-di(2-pyridyl)propane (1), 1,3-bis(2-pyridyl)-2-pentylpropane (2), 1,3-bis(2-pyridyl)-2-phenylpropane (3a), 1,3-bis(2-pyridyl)-2-tolylpropane (4), and 1,3-bis(2-pyridyl)-2-ferrocenylpropane (5) as chelate ligands (L–L) have been synthesized. The crystal structures of 1,3-diphenyl-2,4-di-pyridin-2-yl-butan-1-ol (3b), 5, [(2)PdCl₂], [(4)PdCl₂], and [(5)PdCl₂] have been determined and show a square planar geometry at palladium(II). The neutral complexes were tested in the polymerization of norbornene and copolymerization of norbornene with norbornene derivatives. The complex bearing the pentyl group exhibited high reactivity to give up to 5.9×10⁵ in molecular weight for the homopolymerization. When [(4)PdCl₂] or [(5)PdCl₂] was used as a catalyst, homopolymers insoluble at 150 °C in trichlorobenzene were obtained. However, copolymerization of norbornene with norbornene derivatives 8a–d catalyzed by [(4)PdCl₂] gave soluble copolymers with molecular weights up to 5.1×10⁵.     

Synthesis and structural characterization of cobalt(II) and zinc(II) complexes with 2-(indazol-1-yl)-2-thiazoline (TnInA). X-ray characterization of [CoCl2(TnInA)2] · C2H6O and [(M)(TnInA)2(H2O)2](NO3)2 (M = Co, Zn)

Several complexes of 2-(indazol-1-yl)-2-thiazoline (TnInA) with the divalent ions Co and Zn have been synthesized by the direct combination of the ligand and the metal chloride or nitrate hydrated salts in ethanol. These complexes have been characterized by a variety of physical–chemical techniques. Moreover, the structures of [CoCl₂(TnInA)₂] · C₂H₆O (1) and [(M)(TnInA)₂(H₂O)₂](NO₃)₂ (M = Co, 3; Zn, 4) were determined by single-crystal X-ray diffraction. In all the complexes, the ligand TnInA bonds to the metal ion through the indazole and thiazoline nitrogen atoms. In complex 1 the environment around the cobalt ion may be described as a distorted octahedron with two TnInA ligands and two chlorine ligands. Compounds 3 and 4 are isostructural with a distorted octahedral geometry around the metal center, being linked to two water molecules and two TnInA ligands. However, in complex [ZnCl₂(TnInA)] (2) the zinc atom is four-coordinated with a probable tetrahedral environment with two chloro ligands and one TnInA ligand bonded to the metal ion.     

Synthesis and characterization of bis(2,2′-bipyridine) ruthenium complexes containing thiosemicarbazide ligands: unique redox series

Two series of heterochelates of ruthenium(II) containing two bipyridyl molecules and a bidentate chelating sulfur---nitrogen donor ligand in the form of 4-aryl substituted thiosemicarbazides have been synthesized and characterized. The first series of complexes are dicationic in which the ring substituted 4-aryl thiosemicarbazides (N---S) are chelated in the keto form through the hydrazinic nitrogen and the thione sulfur atom. They are of the [Ru(bpy)₂NS]⁺² type. The second series have the general formula [Ru(bpy)₂NS]⁺¹ in which the thiosemicarbazide moiety remains chelated to the Ru^II centre through the hydrazinic nitrogen and the deprotonated thiolato S-atom. All the complexes have been characterized by elemental analysis, UV-vis, IR and EPR spectroscopy. The complexes were found to constitute a three membered redox series which were investigated by cyclic voltammetry.     

Metal complexes of biologically important ligands: Synthesis of amino acidato complexes of Pd containing a C,N-cyclometallated group as an ancillary ligand

New amino acidato complexes of Pd^II of stoichiometry [Pd(C---N)(Aa)] (C---N=C,N-cyclometallated ligand, Aa = N,O-amino acidato ligand) have been obtained by reaction of [Pd(C---N)(acac)] (C---N=N,N-dimethylbenzylamine-C²,N (dmba) (1) or N,N-dimethyl(S--phenylethyl)amine-C²,N (S-dmphea) (2)) with glycine, chiral amino acids (alanine, phenylalanine and valine), and amino acid derivatives (N-acetylglycine and N-acetyl-,β-dehydroalanine) in MeOH. The compounds are characterized by IR, ¹H and ¹³C NMR. The geometry of these complexes has been unambiguously determined by NOE difference experiments and NOESY measurements.