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New mixed ligand complexes of nickel(II) were synthesized by using dibasic H/5-bromo-/5-chloro-/4-hydroxy-2-hydroxybenzophenone-thiosemicarbazones (L1–4H2) and [Ni(PPh3)2Cl2]. The ligands and complexes were characterized by cyclic voltammetry, infrared, 1H and 31P NMR spectroscopy techniques. Crystallographic analyses of the 5-bromo-substituted (2) and 5-chloro-substituted (3) complexes as representatives were performed and so confirmed the ONS chelate structure and presence of PPh3 as co-ligand in the complexes. To reveal the antioxidant properties of the compounds, TEAC values (by CUPRAC method) were determined along with free radical-scavenging activity (by DPPH method). The compounds bearing 4-hydroxy substituent, L4H2 and complex 4 were the most effective compounds. The relationship between structure and antioxidant capacity in the context of benzophenone substituents and nickel(II) center was evaluated. Electrochemical results revealed that all complexes displayed metal-centered and ligand-centered redox processes. The antioxidant capacities of complexes were well correlated to electrochemical parameters.

A series of mixed-ligand Cu(II) complexes of the type: (i) [Cu(l-pro)(diimine)(H2O)n](ClO4) (n = 0 or 1), where l-pro is l-proline and diimine is 2,2′-bipyridine (bpy; 1), (ii) 4,4′-dimethy...

Tris(glycinato)Mn(III) and its mixed ligand complexes with azido-, thiocyanato-, chloro- and bromo- groups have been synthesized and characterized by UV–Vis spectrophotometry, IR spectropho...

Coordination polymers (CPs) of mixed-ligand lanthanide complexes [Ln2(1,3-pdta)(TPA)(H2O)2]n·nH2O [Ln = La, 1; Ce, 2; Pr, 3; Nd, 4] (1,3-H4pdta = 1,3-propanediaminetetraacetic acid; H2TPA = terephthalic acid) were hydrothermally synthesized with flexible 1,3-pdta and rigid TPA ligands. Moreover, lanthanide propanediaminetetraacetates [Ln(1,3-Hpdta)(H2O)]2n·nH2TPA·xH2O [Ln = Sm, 5; Gd, 6] with multi-layered structures were also obtained. In 1–4, both 1,3-pdta and TPA coordinate with lanthanide ions through carboxyl oxygen and nitrogen atoms. In 5 and 6, only 1,3-Hpdta coordinates with the central lanthanide ion, where one nitrogen atom in 1,3-Hpdta is protonated, and TPAs are crystallized as H2TPA with the central multi-layered structures of [Ln(1,3-Hpdta)(H2O)]2n through very strong hydrogen bonds [2.504(4) Å]. Solid-state 13C NMR analysis of 1 revealed the coordination of carboxyl groups. However, the methylene groups of 1,3-pdta showed an obvious upfield shift, which can be attributed to the effects of the phenyl ring in TPA ligand. The successful synthesis of these mixed-ligand lanthanides provides a rational design of such lanthanide CPs with flexible and rigid ligands.

A new Zn(II) metal-organic framework (MOFs), [Zn(BTC)(HME)]·(DMAc)(H2O) (1, H3BTC =1,3,5-benzenetricarboxylic acid, HME = protonated melamine, DMAc = N,N-dimethylacetamide), has been synthesized un...

Acyclic nucleoside phosphonates (ANPs) are of medical relevance and deserve detailed chemical characterization. We focus here on 1-[2-(phosphonomethoxy)ethyl]cytosine (PMEC), (S)-1-[3-hydroxy-2-(ph...

To study the spectral behavior of Ti(IV) complexes with sulfur donors, several new nano-sized mixed ligand complexes of Ti(IV) have been synthesized by the reaction of titanium(IV) salts with 3(2′-...

Four new mixed-ligand complexes of lead(II) hexafluoroacetylacetonate (hfa) were synthesized and characterized by elemental analyses, IR, 1H and 13C NMR spectroscopy. The single-crystal structure of [Pb2(phen)4(hfa)2(μ-NO3)2] (1) shows the complex to be a dimeric unit as a result of nitrate bridging. The coordination number of Pb(II) is eight with four N-donors from a “phen” and four O-donors from the hexafluoroacetylacetonate and nitrate ligands. This dimeric complex is the first fluorine β-diketonate and nitrate mixed-ligand lead(II) complex that has been characterized by X-ray structural analysis. The supramolecular features in this complex are controlled by weak directional intermolecular interactions and aromatic π–π stacking interactions.

Reactions of pentapseudohalonitrosyl ferrate(II) with β-diketones formed complexes of the type, [Fe(X)3(NO)(L–L)] where X = CN−, NCO− and and L–L = acetylacetonate(acac) and benzoylacetonate (bzac). These compounds have been characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, IR, electronic spectra and thermal gravimetric analysis. Molecular modeling studies have been carried out for structural analysis of some complexes using Hyperchem release 7.52 professional version.

Two new Cd-containing coordination polymers {Cd2(succ)2(1,10′-phen)2} n (1) and {Cd(glut)(1,10′-phen)(H2O)} n (2) are described. Complex 1 exhibits an interesting 2-D structure in which the binuclear Cd centers are linked by succinate anions. Complex 2 possesses an interesting 1-D chain-like structure. The IR and TG properties of the two compounds are studied. Furthermore, these two complexes exhibit photoluminescence.

The copper(II) complex [Cu(L)(en)2]2[Cu(en)2](L)2(ClO4)6, L = 4-2-pyridine-1,2,4-triazole, en = ethylenediamine has been prepared and characterized. Crystals are triclinic, space group P with Z = 1, a = 8.637(3), b = 13.850(4), c = 16.295(5) A, α = 106.662(6), β = 104.039(6), γ = 97.616(6)°, V = 1768.4(10) A3. The structure of the title compound consists of three independent cations with two five-coordinate [Cu(L)(en)2] units and a four-coordinated [Cu(en)2] unit with two weak axial Cu–N interactions to lattice ligand molecules (2.552 A). Other physical properties are described. Both the ligand and the complex fluoresce with different luminescent process.

A new metal-organic coordination polymer, [Fe(4,4′-bpy)(PT)(H2O)2]·2H2O (1) (4,4′-bpy = 4,4′-bipyridine, H2PT = phthalic acid), was prepared by hydrothermal reaction of FeSO4·7H2O, 4,4′-bpy and H2PT at 110°C and characterized by single-crystal X-ray diffraction analysis. The two-dimensional wave-shaped layers are stacked in ABAB sequence, and therefore form a three-dimensional supramolecular architecture. Six-membered rings with the ‘chair’ conformation, formed via hydrogen-bonds, exist between the layers, are symmetrical with respect to the two-fold axes running along b.

The mixed ligand complexes Cd(Hsal)2(Him)2, Cd(Hsal)2(4-MeHim)2, Cd(Hsal)2(4-MeHim)4, Cd(Hsal)2(1,2-diMeim)2 (where Hsal = OHC6H4COO−, Him = imidazole, 4-MeHim = 4-methylimidazole, 1,2-diMeim = 1,2-dimethylimidazole) have been synthesized and characterized. Single-crystal X-ray structures of Cd(Hsal)2(Him)2 and Cd(Hsal)2(1,2-diMeim)2 have been obtained. Gaseous products of their pyrolysis have been investigated and thermal decomposition pathways are postulated for the complexes.

The interaction of acetylsalicylic acid (aspirin, aspH) and nicotinamide (NA) with Co(II) and Ni(II) ions was investigated using square-wave and cyclic voltammetry techniques. In the presence of Ni(II)/Co(II),nicotinamide gave new peaks at -0.85V and soh.12 V, corresponding to the reduction of Ni(II)-nicotinamide(log β1:2 =5.97) and Co(II)-nicotinamide (log β1:2 =5.19) complexes, respectively. In the presence of Ni(II)/Co(II), acetylsalicylic acid gave new peaks at -0.91V and -1.19 V, respectively, corresponding to the reductionof Ni(II)-salicylate (log β1:2 =8.48) and Co(II)-salicylate (log β1:2 =8.14) complexes. In the presence of nicotinamide, Ni(II)-salicylate and Co(II)-salicylate form mixed ligand complexes, reducing at -0.78V (log β1:2:2 =9.68) and -1.14V (log β1:2:2 =8.64), respectively.

The dinuclear 5-coordinate Ni(II) complex [Ni2(taet)(pmdt)2]2+, where taet = 1,1,2,2-tetraacetylethanate and pmdt = N,N,N′,N″,N″-pentamethyldiethylenetriamine, has been prepared and characterized by vibrational and electron spectroscopy and by magnetic measurements. In non-coordinating solvents such as DCE or NM and with non- or weakly coordinating anions like CIO4 − or Bφ4 − these complexes occur as bis-five-coordinate species. In solvents with stronger donor properties (Fa or DMF) and with more strongly coordinating anions, mono- or bis-octahedral species are formed. Spectrophotometric titration was used to evaluate equilibrium constants and associated reaction enthalpies and entropies for the stepwise coordination of donor solvents in DCE. Free energy changes are found to be entropy controlled.

The complexation behaviour of a number of N-methylpropylene diamines with Ag(I) were studied in 1 M KNO3 at 25.00°C potentiometrically, employing pH and pAg measurements. Several metal/ligand ratios were used (varying from 2/1 to 1/8). Complexation of these ligands with Ag(I) in aqueous solution is described by the following species: AgL, AgLH, AgL2, AgL2H, AgL2H2, Ag2L2 and Ag2L2H. No mixed ligand hydroxo species could be detected in the concentration employed. Stability constants of a given species systematically decrease as methylation increases on the terminal amino groups due to increased steric effects.

The hypersensitive transitions 4 I 9/2 → 4 G 5/2' 2 G 7/2 in Nd(III) and 5 I 6' 5 G 6' 5 F 1 in Ho(III) have been studied for fanthanide complexes in aqueous solution with dibasic and polybasic ligands as well as for some mixed ligand complexes. For the dibasic ligands, a linear relation is observed between the oscillator strength of the hypersensitive transition and the sum of the ligand pKa values. With ligands which contain both N and O coordination sites, the correlation holds when only the basicity of the O sites is considered.

Studies have been made on the coordination behaviour of the aluminium(III) 8-quinolinol-5-sulfonate (hqs)1 and aluminium(III) nqs1 complexes2 with hqs in 0.1 mol dm−2 aqueous sodium chloride solution at 25°. Mixed-ligand complex formation was evidenced by electronic absorption spectral and other spectrophotometric equilibrium studies. Stopped-flow kinetic studies revealed that mixed-ligand complex formation with a mono-nqs complex proceeds via its reaction with Hhqs− and hqs2- whereas formation of the tris-hqs complex proceeds via the reaction of [Al(H2O)6]3+ with Hhqs− and hqs2- and also of [Al(OH)(H2O)5]2+ with H2 hqs and Hhqs−. Coordination mechanisms and structures for the mixed-ligand and the tris-hqs complexes are also discussed.

Complexes of Nickel(II) and Cobalt(II) containing triphenylphosphine and N, N-dimethylformamide (DMF) or dimethylsulphoxide (DMSO) are reported. These are of the type Ni(PPh3)L2X2 (L=DMF or DMSO, and X=Cl or Br) and CoX2(PPh3)L (L=DMF or DMSO, and X=Cl or Br). These have been synthesised by two different methods and characterised with the help of elemental analyses and various physical data, including infrared and electronic spectra, magnetic measurements, conductivity measurements and thermogravimetric analyses.

The formation constants of complexes of the type [CuAL], where A = 2, 2′-dipyridyl, 1, 10-phenanthroline, 2-(2′-pyridyl)benzimadazole, or 2-(2′-pyridyl)imidazoline and L = salicylaldehyde, 5-bromosalicylaldehyde, 5-nitrosalicylaldehyde, 2-hydroxyacetophenone, or 2-hydroxy-l-naphthaldehyde have been determined in dioxan-water (1:1 v/v) solutions and μ = 0.2 mol dm−3 NaClO4 at 30°. The formation constants have been determined by a graphical method and further refined using a computer programme. The values of Δlog K (log KMAL MA - log KML M) is positive. ΔLog K is less positive in the case of complexes involving 2-hydroxyl-l-naphthaldehyde, nitrosalicylaldehyde and bromosalicylaldehyde. The solid mixed ligand complexes have been isolated.

A novel chelate exchange reaction, leading to the formation of a series of N-alkyl substituent dependent mixed ligand isomeric complexes of the type Ni(R–AB)(AC') and Ni(R–AC)(AB') (Figure 1) are discussed. Here, AB and AC denote two different N-bonded isonitroso-β-keto-imino ligand moieties, while AB' and AC' are the corresponding O-bonded ligand moieties and R is an N-alkyl substituent. The isomeric complexes are suggested to be monomeric, neutral and diamagnetic with an asymmetric square planar geometry. The bonding isomerism of the isonitroso group in these complexes is discussed on the basis of the infrared and proton magnetic resonance spectral studies. A probable mechanism for the preparative route is also proposed.

The complexes RuCl/sub 2/(PPh/sub 3/)/sub 3/ and RuCl/sub 3/(AsPh/sub 3/)/sub 2/(MeOH) were employed as convenient starting materials. Methods were developed to prepare cis- or trans-isomers of the type RuCl/sub 2/L/sub 4/ (L = AsMePh/sub 2/, AsMe/sub 2/Ph) starting from RuCl/sub 2/(PPh/sub 3/)/sub 3/. Meridonial complexes of the type RuCl/sub 3/L/sub 3/ (L = PPh/sub 3/, PMePh/sub 2/, PMe/sub 2/Ph, PEtPh/sub 2/) were obtained by the reaction of Wilkinson's green complex, RuCl/sub 3/(AsPh/sub 3/)/sub 2/(MeOH) with an excess of L in benzene. In the presence of a large excess of methyldiphenylphosphine in benzene, a five coordinate complex RuCl/sub 2/(PMePh/sub 2/)/sub 3/ was obtained. The temperature of the reaction and solvent decide the nature of the reaction product. Thus a polymeric complex of the composition (RuCl/sub 2/(AsPh/sub 3/)/sub 2/)/sub n/ was obtained from RuCl/sub 3/(AsPh/sub 3/)/sub 2/(MeOH) with triphenylarsine in boiling propanol. The reaction of RuCl/sub 3/.3H/sub 2/O with PPh/sub 3/ and then AsPh/sub 3/ in propanol gave mixed ligand polymers of the type (RuCl/sub 2/(PPh/sub 3/)(AsPh/sub 3/))/sub n/.

Four mixed tetradentate Cu(II) chelates were prepared by reacting a copper salt, acety acetone, and ethylene-diamine with salicylaldehyde, o-hydroxyacetophenone, o-hydroxypropiophenone, and o-hydroxybutyrophenone, respectively. The I.R., optical, and E.S.R. spectra were obtained and discussed with regard to the expected bonding changes and/or those predicted by a model molecular orbital calculation for mixed ligand complexes.

We have recently reported the results of a conformational analysis (strain energy minimization calculation) of the stereoisomers of some cobalt (III) complexes with the stereospecific chelating agent N,N'-bis-(2-picolyl)-1,2(S)-propanediamine (picpn)1. We have extended these calculations to include the mixed ligand complexes, [Co(picpn)gly]2+, [Co(picpn)R-ala]2+ and [Co(picpn)S-ala]2+. Our interest in these compounds arises from recent reports of the synthesis of optically active amino acids via hydrogenation of appropriate precursors in the presence of chiral metal complexes2,3,4, one of which contains heterocyclic nitrogen donors.5