Nickel(II) complexes with amino-and iminocyclohexylsulfides: Synthesis and electrochemical study

Nickel(II) complexes with aminosulfide and iminosulfide ligands have been synthesized on the basis of phenyl-and ethynyl-(2-aminocyclohexyl)sulfides, glyoxal hydrate, and Ni(ClO₄)₂ · 6H₂O. Electrochemical measurements were carried out using cyclic voltammetry (CVA) and a rotating disk electrode (RDE). The following has been shown: (1) the reduced species of iminosulfide complexes are more stable than the reduced species of aminosulfide complexes, and (2) the complexes containing a C≡C fragment in their organic ligand are polymerized during reduction.     

Synthesis and spectroscopic study of copper(II) and manganese(II) complexes with pipemidic acid

The interaction of copper(II) and manganese(II) with pipemidic acid, Hpipem, afforded the complexes [Cu(pipem)(2)(H(2)O)] x 2H(2)O, 1 and [Mn(pipem)(2)(H(2)O)], 2. The new complexes have been characterised by elemental analyses, infrared, UV-vis and X-band EPR spectroscopy in the temperature range from 4 to 300 K. The monoanion, pipem, exhibits O,O ligation through the carbonyl and carboxylato oxygen atoms. Five coordinate square-pyramid configuration has been proposed for 1 and 2, and the fifth apical position is occupied by a coordinated water molecule.     

Palladium(II)-dppe-arylazoimidazole complexes: Synthesis,and spectroscopic characterization

Reaction of [Pd(dppe)Cl₂/Br₂] with AgOTf in a dichloromethane medium followed by ligand addition led to [Pd(dppe)(OSO₂CF₃)₂] and then [Pd(dppe)(RaaiR)](OSO₂CF₃)₂ [RaaiR′ = p-R-C₆H₄-N=N-C₃H₂-NN-1-R′, (1–3), abbreviated as a N,N′-chelator, where N(imidazole) and N(azo) are represented by N and N′, respectively; R = H (a), Me (b), Cl (c) and R′ = Me (1), CH₂CH₃ (2), CH₂Ph (3), OSO₂CF₃ is the triflate anion, dppe = 1,2-bis-(diphenylphosphinoethane)]. ³¹P “¹H” NMR confirmed that due to the two phosphorus atom interaction in the azoimine symmetrical environment one sharp peak was formed. The ¹H NMR spectral measurements suggest that azo-imine link with lot of phenyl protons in the aromatic region. ¹³C (¹H) NMR spectrum, ¹H, ¹H COSY and ¹H, ¹³C HMQC spectrum assign the solution structure and stereo-retentive conformation in each complex.     

Nickel(II) complexes with cytosine and threonine: Synthesis and structure

Mono-and mixed-ligand complexes with the composition [Ni(Cyt)₂(H₂O)₂]Cl₂, [Ni(Thr^–)₂(H₂O)₂] and [Ni(Thr^–)(Cyt)(H₂O)₂]Cl are synthesized and studied. Using IR spectroscopy it is determined that in the complex compounds, cytosine is bidentate (C=O group oxygen and heterocycle N3), threonine interacts with the Ni(II) ion due to amino and carboxyl groups. The models of the atomic structure of the studied compounds are proposed based on the EXAFS and XANES spectroscopy results.     

Synthesis and spectroscopic characterization of cobalt(II) thiosemicarbazone complexes

Thiosemicarbazone derivatives are formed on reaction between acetophenone, salicylaldehyde, benzophenone and/or 2-hydroxy-4-methoxybenzophenone and thiosemicarbazide or its N⁴H substituents (ethyl-, phenyl-, and p-chlorophenyl-). The ligands were investigated by elemental analysis and spectral (IR, ¹H?NMR and MS) studies. The formulas of the prepared complexes have been suggested by elemental analyses and confirmed by mass spectra. The coordination sites of each ligand were elucidated using IR spectra revealing bidentate and tridentate coordination. Different geometries for the complexes were proposed on the basis of electronic spectra and magnetic measurements. The complexes have been analyzed thermally (TG and DTG) and the kinetic parameters for some of their degradation steps were calculated.     

Nickel(II) complexes with different chromospheres containing macrocyclic ligands: spectroscopic and electrochemical studies

The mixed donor tetradentate (L(1)=N(2)O(2)) and pentadentate (L(2)=N(2)O(2)S) ligands have been prepared by the interaction of 1,3-diaminopropane and thiodiglycolic acid with diamine. These ligands possess two dissimilar coordination sites. Different types of complexes were obtained which have different stoichiometry depending upon the type of ligands. Their structural investigation have been based on elemental analysis, magnetic moment and spectral (ultraviolet, infrared, (1)H NMR, (13)C NMR and mass spectroscopy methods). The Ni(II) complexes show magnetic moments corresponding to two unpaired electrons except [Ni(L(1))](NO(3))(2) which is diamagnetic. Ligand field parameters of these complexes were compared. N(2)O(2)S donor ligand complexes show higher values of ligand field parameters, which are used to detect their geometries. The redox properties and stability of the complexes toward oxidation waves explored by cyclic voltammetry are related to the electron-withdrawing or releasing ability of the substituents of macrocyclic ligands moiety. The Ni(II) complexes displayed Ni(II)/Ni(I) couples irreversible waves associated with Ni(III)/Ni(II) process.     

Nickel(II) and cobalt(II) complexes of rhodanine

Summary Nickel(II) and cobalt(II) complexes of rhodanine (Hrd) were prepared from the metal chloride or acetate and the ligand. With an excess of NH3, the octahedral [Ni(NH₃)₆](Rd)₂ and [Co(NH₃)₅Rd]Rd complexes are ob-tained; use of only two NH₃ equivalents per metal ion yields the Ni(Rd)₂ sd HRd · NH₃ and [Co(Rd)₂ ] · 1.5 H₂O complexes, the first with tetragonally distorted hexacoordination and the second with polymeric octahedral coordination. By using two equivalents of NaOH per metal ion, the binuclear [Ni(Rd)₂][Ni(Rd)₂ · (HRd)₂] · 2 H₂O complex is formed having one diamagnetic planar and one high spin octahedral chromophore. Rhodanine is coordinated through the thiocarbonylic sulphur in the neutral form and through the thiocarbonylic sulphur and the deprotanated nitrogen atoms in the rhodanidato anionic form.     

Synthesis and spectroscopic characterization of CN-substituted bipyridyl complexes of Ru(II)

A series of ruthenium complexes having the general form [Ru(bpy)(3-n)(CN-Me-bpy)(n)](PF(6))(2) (where bpy = 2,2'-bipyridine, CN-Me-bpy = 4,4'-dicyano-5,5'-dimethyl-2,2'-bipyridine, and n = 1-3 for complexes 1-3, respectively) have been synthesized and characterized using a variety of steady-state and nanosecond time-resolved spectroscopies. Electrochemical measurements indicate that the CN-Me-bpy ligand is significantly easier to reduce than the unsubstituted bipyridine (on the order of ～500 mV), implying that the lowest energy (3)MLCT (metal-to-ligand charge transfer) state will be associated with the CN-Me-bpy ligand(s) in all three compounds. Comparison of the Huang-Rhys factors derived from spectral fitting analyses of the steady state emission spectra of complexes 1-3 suggests all three compounds are characterized by excited-state geometries that are less distorted relative to their ground states as compared to [Ru(bpy)(3)](PF(6))(2); the effect of the more nested ground- and excited-state potentials is reflected in the unusually high radiative quantum yields (13% (1), 27% (2), and 40% (3)) and long (3)MLCT-state room-temperature lifetimes (1.6 μs, 2.6 μs, and 3.5 μs, respectively) for these compounds. Coupling of the π* system into the CN groups is confirmed by nanosecond step-scan IR spectra which reveal a ～40 cm(-1) bathochromic shift of the CN stretching frequency, indicative of a weaker CN bond in the (3)MLCT excited state relative to the ground state. The fact that the shift is the same for complexes 1-3 is evidence that, in all three complexes, the long-lived excited state is localized on a single CN-Me-bpy ligand rather than being delocalized over multiple ligands.     

Vibrational spectroscopic study on pyrimidine metal(II) tetracyanometalate complexes

The results of an infrared and Raman spectroscopic study are reported for seven new metal(II) pyrimidine tetracyanonickelate complexes, M(pyr)2Ni(CN)4 [where (pyr) = pyrimidine; M = Mn, Fe, Co, Zn, Ni, Cu or Cd] and an IR spectroscopic study is presented for new cadmium pyrimidine tetracyanometalate complex, Cd(pyr)2Cd(CN)4. The spectral data suggest that the first seven compounds belong to the Hofmann-type and the last compound belongs to the Hofmann-Td-type of complexes.     

Heteroarylphosphorus compounds: Nickel(II) and cobalt(II) complexes of thienylphosphines

Complexes of a series of tertiary phosphines bearing 2-thienyl groups with nickel(II) and cobalt(II) halides and thiocyanates have been prepared and their magnetic and spectroscopic properties are presented. The nickel(II) halide and cobalt(II) halide and thiocyanate complexes have a distorted tetrahedral structure, whereas the nickel(II) thiocyanate complexes are square planar. Consideration of the spectroscopic data for the tetrahedral nickel(II) halide complexes of the thienylphosphines indicates that a 2-thienyl substituent is more electron-releasing towards phosphorus than is a phenyl group when the phosphorus is coordinated to the metal, suggesting that in this situation effects of pπ−dπ interactions between the heterocyclic ring system and phosphorus may be significant in influencing the donor properties of the phosphine. Calculation of the Racah parameters for the nickel(II) complexes indicates that the nephelauxetic effects of the thienylphosphines are different from those of triphenylphosphine and that there is a greater degree of covalency in the metal-ligand bond in the case of the thienylphosphines.     

Synthesis,structure and spectroscopic study of Cu(II) polypyridine complexes with phenylcyanamide derivative ligands

Several new mononuclear copper(II) complexes, [Cu(phen)₂L]PF₆, where phen = 1,10-phenanthroline and L = monoanions of phenylcyanamide (pcyd), 2,5-dichlorophenylcyanamide (2,5-Cl₂pcyd), 2-dichlorophenylcyanamide (2-Clpcyd) and 4-methylphenylcyanamide (4-Mepcyd), have been prepared and characterized by elemental analysis, UV–Vis, IR and ¹H NMR spectroscopies and cyclic voltammetry. [Cu(phen)₂(2,5-Cl₂pcyd)]PF₆ crystallized with a molecule of acetone with empirical formula of C₃₁H₂₀N₆OF₆Cl₂PCu in a triclinic crystal system and space group P 1 with a = 9.2086(6) Å, b = 13.3117(9) Å, c = 15.5313(10) Å, α = 107.8210(10)°, β = 104.6180(10)°, γ = 104.1670(10)°, V = 1643.21(19) ų and Z = 2. The structure was refined using 7555 Mo-Kα reflections with I > 2σ(I) and R ₁ = 0.0276 and Rw = 0.0692. The results are consistent with a mostly σ bonding interaction between Cu(II) and cyanamide anion. The LMCT band intensity and electrochemical potentials are compared with ruthenium phenylcyanamide analogues.     

Nickel(II) complexes of oligopeptides containing aspartyl and glutamyl residues. Potentiometric and spectroscopic studies

Nickel(II) complexes of di-, tri- and tetra-peptides built up from Asp and/or Glu residues have been studied by potentiometric, UV–Vis and circular dichroism spectroscopic methods. The stoichiometry of the complexes are the same as in the case of common oligopeptides, but the presence of the side chain carboxylate groups results in differences in their stabilities and coordination modes. The presence of the β-carboxylate groups increases the metal binding affinity of the peptides in all cases. This is due to the coordination of the first, second and third aspartic acid residue in the case of the NiL, NiH₋₁L and NiH₋₂L complexes, respectively. The high negative charge of Asp₄ suppresses the metal ion coordination of the third amide function, therefore the NiH₋₃L complex does not form with this tetra-peptide. In the case of peptides containing glutamic acid, no stability enhancement appears because there is only a weak interaction between the nickel(II) ion and the γ-carboxylate group, which is not able to compensate the disfavoured effect of the increasing negative charge of the complexes.     

Nickel(II) complexes of biologically active glutathione: spectroscopic, kinetics of thermal decomposition and XRPD studies

Nickel(II) complexes of reduced glutathione (GSH) of general composition Na[Ni(L)(X)]H(2)O, where H(2)L=GSH; X=NO(3)(-), SCN(-), CH(3)CO(2)(-), Cl(-) have been synthesized and characterized by elemental analysis, infrared spectra, electronic spectra, magnetic susceptibility measurements, thermal and X-ray powder diffraction studies. Infrared spectra indicate deprotonation and coordination of cysteinyl sulphur and carboxylate oxygen of glycine residue with nickel ions. It indicates the presence of water molecule in all the complexes which has been supported by TG/DTA. The thermal behavior of complexes shows that water molecule is removed in first step-followed removal of anions and then decomposition of the ligand molecule in subsequent steps. General mechanisms describing the decomposition of the solid complexes are suggested. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. The room temperature magnetic moment values for all the complexes lie in the range of 2.2-2.4BM, indicating departure from spin only values due to second order Zeeman effect. The electronic spectra indicate planar coordination geometry for all the complexes. Crystal data for Na[Ni(L)(CH(3)CO(2)(-))]H(2)O: tetragonal, space group P4/m, a=8.2004A, b=8.2004A, c=16.0226A, V=1077.47A(3), Z=2. Crystal data for Na[Ni(L)(Cl(-))]H(2)O: cubic, space group Pm3, a=16.1055A, b=16.1055A, c=16.1055A, V=4178.38A(3), Z=6. Crystal data for Na[Ni(L)(NO(3)(-))]H(2)O: tetragonal, space group P4/m, a=7.2121A, b=7.2121A, c=12.0200A, V=625.22A(3), Z=2.     

Nickel(II) complexes with dicyanamide and tetramines

Four new pseudohalide complexes of the type [NiL{N(CN)₂}₂] (L = N(CH₂CH₂NH₂)₃, TAA; triethylenetetramine, TTA) and [NiL{N(CN)₂}]ClO₄ have been prepared and characterized by spectroscopic and magnetic methods. The X-ray crystal structures of [Ni(TAA){N(CN)₂}₂] and [Ni(TTA){N(CN)₂}₂] have been determined, and analyses show that in both complexes the Ni ion posseses distorted octahedral geometry. The temperature dependence of the magnetic susceptibility of [Ni(TTA){N(CN)₂}](ClO₄) was measured, but no antiferromagnetic interaction was detected.     

Synthesis and spectroscopic characterization of Zn(II), Cd(II), and Hg(II) ciprofloxacin complexes

Ciprofloxacin metal co mplexes with general for mula [M(CPF)₂]X₂·nH₂O [M = Zn(II), Cd(II), and Hg(II)] have been synthesised and characterized using elemental analysis (CHN), spectroscopic (UV-Vis, IR, MS, and ¹H NMR) and ther mogravimetric (TG and DTA) data. Using the Coats-Redfern and Horowitz-Metzeger methods, kinetic analysis of the thermogravimetric data had been performed.     

Nickel(II) and Copper(II) complexes of sulphamide and ethylenediamine

Summary The following ethylenediamine(sulphamide)nickel(II) and ethylenediamine(sulphamide)copper(II) complexes were prepared: Ni(en)₃(H₂Su)Cl₂, in which H₂Su is not coordinated; Ni(en)₂(H₂Su)Cl₂ , Ni(en)₂(HSu)Cl · EtOH, Ni(en)₂(HSu)₂,Ni(en)₂(HSu)₂(H₂Su)₂ · EtOH, Cu(en)₂(HSu)₂(H₂Su) · O.5EtOH, in which the sulphamide molecule, H₂Su, or the sulphamidato anion [HSu] are totally or partially coordinated. The comparison of the i.r. spectra of these complexes with those of H₂ Su and NaHSu and with those of the M(en)₂Cl₂ complexes permits the isolation of the sulphamide or sulphamidato (SO₂) and (SN₂) bands which show oxygen-coordination of these ligands to the metal. Some (MO) bands were identified in the far i.r. region.     

Synthesis and spectroscopic characterization of cadmium(II) complexes of thiones and thiocyanate

Cadmium(II) complexes of thiones and thiocyanate, [(>C=S)₂Cd(SCN)₂], have been prepared and characterized by IR and NMR spectroscopy. An upfield shift in the >C=S resonance of thiones in the ¹³C NMR and downfield shift in N–H resonance in ¹H NMR are consistent with sulfur coordination to cadmium(II). The presence of ν(N–H) of thiones in IR spectra of the complexes indicates the thione forms of the ligands in the solid state; some contribution of the thiolate form was observed in one complex. The appearance of a band around 2100 cm^?1 in IR and a resonance around 132 ppm in ¹³C NMR indicates the binding of thiocyanate to cadmium(II).     

Potentiometric and spectroscopic study of selenomethionine complexes with copper(II) and zinc(II) ions

Summary The stepwise stability constants of 1:1 and 2:1 complexes of selenomethionine (SeMet) with Cu^II and Zn^II ions have been determined in NaNO₃ (0.1m) supporting electrolyte by potentiometric titration at 25 °C. The overall log stability constant (logML₂ = [ML₂]/[M²⁺][L^–1]²) for Cu^II and Zn^II complexes are 14.50 and 8.75, respectively. Two new solids were prepared and identified by elemental microanalysis as (SeMet)₂Cu and (SeMet)₂Zn. I.r. and Raman spectral studies indicated metal coordination with the nitrogen and oxygen atoms of the amino acidato group of SeMet. The corresponding stretching bands were assigned at 341.1cm^– for Cu-O, 352.9 cm^– for Zn-O, 497.3 cm^– for Cu-N and 475.2 cm^– for Zn-N bonds.     

Nickel(II) complexes of methylphosphinediacetic acid

Methylphosphinediacetic acid (H₂G) is coordinated to nickel(II) in two different ways, depending on whether its carboxyl groups are protonated or dissociated. The acid behaves as a monodentate tertiary phosphine in that it yields a series of trans-square planar NiX₂(H₂G)₂ complexes (X = Cl, Br, NCS or CN) which are stable in the solid state and as solutions in polar non-aqueous solvents. In neutral aqueous solution the NiG₂²⁻ complex is the predominant species (logβ₂ = 8.24 at 25°C and I = 0.1) even in excess nickel(II). Solid NiG·4H₂O is the nickel salt of this anion, Ni[NiG₂]·8H₂O. The X-ray structural determination of the barium salt, BaNiG₂·NaClO₄·5H₂O, revealed the uncommon cis-square planar arrangement around nickel with the G₂₋ anions acting as chelating P,O-bidentate to nickel and as O-monodentate to barium. Sodium and perchlorate ions are located between the complex units and, surprisingly, cannot be removed on recrystallization.     

Nickel(II) complexes with 4-aminobenzophenone

The following nickel(II) complexes with 4-aminobenzophenone (L) have been prepared and investigated: NiBr₂L_0.67, Ni(NO₃)₂L, NiX₂L₂(X = Cl(H₂O), NO₃), NiCl₂L₃, NiX₂L₄(X = Br, I, BF₄, ClO₄(2H₂O)), NiX₂L₆(X = BF₄, NO₃) and Ni(ClO₄)₂L₈. In the NiCl₂L₂.H₂O, Ni(NO₃)₂L, Ni(NO₃)₂L₂ and Ni(NO₃)₂L₆ complexes the ligand is H₂N-coordinated. In the other complexes the coordination occurs through the carbonylic oxygen atom. Some νNiX(X = Cl, Br, I, ONO₂) and νNiN bands and the νNiOH₂ band of the NiCl₂L₂.H₂O complex were assigned.