Equilibrium studies on mixed ligand complex formation of Co(II), Ni(II), Cu(II) and Zn(II) with N-(2-hydroxybenzyl)-L-histidine (H(2)hb-L-his) and typical N,N donor ligands: Crystal structure of [Ni(hb-L-his)(bipyridine)]center dot H2O complex

Equilibrium study on complex formation of Co(II), Ni(II), Cu(II) and Zn(II), hereafter M(II), with the quadridentate (O-, N, O-, N) donor ligand, N-(2-hydroxybenzyl)-L-histidine (H(2)hb-L-his, hereafter H2L), in the absence and in the presence of typical (N, N) donor bidentate ligands, 1,10 phenanthroline(phen), 2, 2'-bipyridine(bipy), ethylenediamine(en), hereafter B, in aqueous solution at 25 +/- 1 degrees C was done at a fixed ionic strength, I = 0.1 mol dm(-3) (NaNO3) by combined pH-metric, UV-Vis and EPR measurements provide evidence for the formation of mononuclear and dinuclear binary and mixed ligand complexes of the types: M(L), M(L)(2)(2-), M-2(L)(2+), M-2(H-1L)(+), M(L)(B), (B)M(H-1L)M(B)(+). The imidazole moiety of the ligand is found to act as a bridging bidentate ligand in the dinuclear M-2(L)(2+), M-2(H-1L)(+) and (B)M(H-1L)M(B)(+) complexes, using its N-3 atom and N1-H deprotonated moiety. Stability constants of the complexes provide evidence of discrimination of Cu(II) from the other M(II) ions by this ligand. Solid complexes: [Ni(L)(H2O)(2)] (1), [Cu(L)(H2O)] (2), and [Ni(L)(bipy)] (.) H2O (3) have been isolated and characterized by various physicochemical studies. Single crystal X-ray diffraction of the ternary complex, 3, shows an octahedral [(O-,N,N,O-)(N,N)] geometry with extensive pi-pi stacking of the aromatic rings and H-bonding with imidazole (N1-H), secondary amino N-atom, the lattice H2O molecule, and the carboxylate and phenolate O-atoms. (c) 2006 Elsevier B.V. All rights reserved.

Construction of coordination polymers of cadmium(II) with mixed hexamethylenetetramine and terephthalate or thiocyanate ligands

Three new polymeric complexes [Cd(hmt)(SCN)(2)(H2O)(2)](n) (1), [Cd-3(mu(2)-hmt)(2)(SCN)(6)(H2O)(2)](n) (2), and [Cd-2(hmt)(2)(tP)(2)(H2O)(6)](n) (3) [hmt = hexamethylenetetramine, tp = terephthalate] have been synthesized and characterized by single crystal X-ray diffraction. Both the compounds 1 and 2 are 1-D polymers where Cd units are linked by double end-to-end thiocyanate bridges but in 2 the chain is wider containing three cadmium atoms instead of one as found in 1. In both compounds the coordination environment around cadmium atom is distorted octahedral. Compound 3 is a three-dimensional polymer having water-filled microporous channels. Both tp and brut are mu(2)-bridged. One of the acid groups of tp is coordinated in chelating bidentate and the other in monodentate fashion. Half of its Cd atoms are hexa-coordinated and the rest are hepta-coordinated. Thermogravimetric analysis and X-ray diffraction study of 3 show that its framework remains intact upon removal of water molecules. The flexibility of coordination number around cadmium atoms (six or seven) probably plays an important role in establishing the rigidity of the framework. (C) 2003 Elsevier Ltd. All rights reserved.

Dinuclear complexes of M-II thiocyanate (M = Ni and Cu) containing a tridentate Schiff-base ligand: synthesis, structural diversity and magnetic properties

A dinuclear Ni-II complex, [Ni-2(L)(2)(H2O)(NCS)(2)]center dot 3H(2)O (1) in which the metal atoms are bridged by one water molecule and two mu(2)-phenolate ions, and a thiocyanato-bridged dimeric Cull complex, [Cu(L)NCS](2) (2) [L = tridentate Schiff-base ligand, N-(3-aminopropyl)salicylaldimine, derived from 1:1 condensation of salicylaldehyde and 1,3-diaminopropane], have been synthesized and characterized by IR and UV/Vis spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction studies. The structure of 1 consists of dinuclear units with crystallographic C-2 symmetry in which each Ni-II atom is in a distorted octahedral environment. The Ni-O distance and the Ni-O-Ni angle, through the bridged water molecule, are 2.240(11) angstrom and 82.5(5)degrees, respectively. The structure of 2 consists of dinuclear units bridged asymmetrically by di-mu(1,3)-NCS ions; each Cull ion is in a square-pyramidal environment with tau = 0.25. Variable-temperature magnetic susceptibility studies indicate the presence of dominant ferromagnetic exchange coupling in complex 1 with J = 3.1 cm(-1), whereas complex 2 exhibits weak antiferromagnetic coupling between the Cu-II centers with J = -1.7 cm(-1). ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Ultrafast excited state dynamics controlling photochemical isomerization of N-methyl-4-[trans-2-(4-pyridyl)ethenyl]pyridinium coordinated to a {Re-1(CO)(3)(2,2 '-bipyridine)} chromophore

Two Multifunctional photoactive complexes [Re(Cl)(CO)(3)-(MeDpe(+))(2)](2+) and [Re(MeDpe(+))(CO)(3)(bpy)](2+) (MeDpe(+) = N-methyl-4-[trans-2-(4-pyridyl)ethenyl]pyridinium, bpy = 2,2'-bipyridine) were synthesized. characterized. and their redox and photonic properties were investigated by cyclic voltammetry: ultraviolet-visible-infrared (UV/Vis/IR) spectroelectrochemistry, stationary UV/Vis and resonance Raman spectroscopy; photolysis; picosecond time-resolved absorption spectroscopy in the visible and infrared regions: and time-resolved resonance Raman spectroscopy. The first reduction step of either complex Occurs at about -1.1 V versus Fc/Fc(+) and is localized at MeDpe(+). Reduction alone does not induce a trans -> cis isomerization of MeDpe(+). [Re(Cl)(CO)(3)(MeDPe(+))(2)](2+) is photostable, while [Re(MeDpe(+))(CO)(3)(bpy)](2+) and free MeDpe(+) isomerize under near-UV irradiation. The lowest excited state of [Re(Cl)(CO)(3)(MeDPe(+))(2)](2+) has been identified as the Re(Cl)(CO)(3) -> MeDpe(+) (MLCT)-M-3 (MLCT = metal-to-ligand charge transfer), decaying directly to the ground state with lifetimes of approximate to 42 (73%) and approximate to 430ps (27%). Optical excitation of [Re(MeDpe(+))(CO)(3)(bpy)](2+) leads to population of Re(CO)(3) -> MeDpe(+) and Re(CO)(3) -> bpy (MLCT)-M-3 states, from which a MeDpe(+) localized intraligand 3 pi pi* excited state ((IL)-I-3) is populated with lifetimes of approximate to 0.6 and approximate to 10 ps, respectively. The 3IL state undergoes a approximate to 21 ps internal rotation, which eventually produces the cis isomer on a much longer timescale. The different excited-state behavior of the two complexes and the absence of thermodynamically favorable interligand electron transfer in excited [Re(MeDpe(+))(CO)(3)(bpy)](2+) reflect the fine energetic balance between excited states of different orbital origin, which can be tuned by subtle Structural variations. The complex [Re(MeDpe+)(CO)(3)(bpy)](2+) emerges as a prototypical, multifunctional species with complementary redox and photonic behavior.

Synthesis, characterization, and anion selectivity of copper(II) complexes with a tetradentate Schiff base ligand

A new mononuclear Cu(II) complex, [CuL(ClO4)(2)] (1) has been derived from symmetrical tetradentate di-Schiff base, N,N'-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L) and characterized by X-ray crystallography. The copper atom assumes a tetragonally distorted octahedral geometry with two perchlorate oxygens coordinated very weakly in the axial positions. Reactions of I with sodium azide, ammonium thiocyanate or sodium nitrite solution yielded compounds [CuL(N-3)]ClO4 (2), [CuL(SCN)ClO4 (3) or [CuL(NO2)]-ClO4 (4), respectively, all of which have been characterized by X-ray analysis. The geometries of the penta-coordinated copper(H) in complexes 2-4 are intermediate between square pyramid and trigonal bipyramid (tbp) having the Addition parameters (tau) 0.47, 0.45 and 0.58, respectively. In complex 4, the nitrite ion is coordinated as a chelating ligand and essentially both the 0 atoms of the nitrite occupy one axial site. Complex 1 shows distinct preference for the anion in the order SCN- > N-3(-) > NO2- in forming the complexes 24 when treated with a SCN-/N-3(-)/NO2- mixture. Electrochemical electron transfer study reveals (CuCuI)-Cu-II reduction in acetonitrile solution. (c) 2006 Elsevier B.V.. All rights reserved.

Anion directed templated synthesis of mono- and di-Schiff base complexes of Ni(II)

Two sets of Schiff base ligands, set-1 and set-2 have been prepared by mixing the respective diamine (1,2-propanediamine or 1,3-propanediamine) and carbonyl compounds (2-acetylpyridine or pyridine-2-carboxaldehyde) in 1:1 and 1:2 ratios, respectively and employed for the synthesis of complexes with Ni(II) perchlorate and Ni(II) thiocyanate. Ni(II) perchlorate yields the complexes having general formula [NiL2](ClO4)(2) (L = L-1 [N-1-(1-pyridin-2-yl-ethylidine)-propane-1,3-diamine] for complex 1, L-2 [N-1-pyridine-2-ylmethylene-propane1,3-diamine] for complex 2 or L-3 [N-1-(1-pyridine-2-yl-ethylidine)-propane-1,2-diamine] for complex 3) in which the Schiff bases are mono-condensed terdentate whereas Ni(II) thiocyanate results in the formation of tetradentate Schiff base complexes, [NiL](SCN)(2) (L=L-4 [N,N'-bis-(1-pyridine-2-yl-ethylidine)-propane-1,3-diamine] for complex 4, L-5 [NN'-bis(pyridine-2-ylmethyline)-propane-1, 3-diamine] for complex 5 or L-6 [NN'-bis-(1-pyridine-2-yl-ethylidine)-propane- 1, 2-diamine] for complex 6) irrespective of the sets of ligands used. Formation of the complexes has been explained by anion modulation of cation templating effect. All the complexes have been characterized by elemental analyses, spectral and electrochemical results. Single crystal X-ray diffraction studies confirm the structures of four representative members, 1, 3, 4 and 5; all of them have distorted octahedral geometry around Ni(II). The bis-complexes of terdentate ligands, I and 3 are the mer isomers and the complexes of tetradentate ligands, 4 and 5 possess trans geometry. (c) 2007 Elsevier Ltd. All rights reserved.

Facile synthesis of Cu(II) complexes of monocondensed N,N,N donor Schiff base ligands: crystal structure, spectroscopic and magnetic properties

Four new copper(II) complexes, [((CuLN3)-N-1)(2)](ClO4)(2) (1), [(CuL2 N-3)(2)](ClO4)(2) (2), [CuL3(N-3)ClO4)](n) (3) and [CuL4(mu-1,1-N-3)(mu-1,3-N-3)(ClO4)](n) (4) where L-1 = N-1-pyridin-2-yl-methylene-propane-1,3-diamine, L-2 = N-1-(1-pyridin-2-yl-ethylidene)propane-1,3-diamine, L-3 =N-1-(1-pyridin-2-yl-ethylidene)ethane-1,2-diamine and L-4=N-1-(1-pyridin-2-yl-ethylidene)propane-1,2-diamine are four tridentate N,N,N donor Schiff base ligands, have been derived and structurally characterized by X-ray crystallography. Compounds 1 and 2 consist of double basal-apical end-on (EO) azide bridged dinuclear Cu-II complexes with square-pyramidal geometry. In complex 3 the square planar mononuclear [CuL3 (N-3)] units are linked by weakly coordinated perchlorate ions in the axial positions of Cu-II to form a one-dimensional chain. Two such chains are connected by hydrogen bonds involving perchlorate ions and azide groups. Compound 4 consists of 1-D chains in which the Cu-II ions with a square-pyramidal geometry are alternately bridged by single EO and end-to-end (EE) azido ligands, both adopting a basal-apical disposition. Variable temperature (300-2 K) magnetic susceptibility measurements and magnetization measurements at 2 K have been performed. The results reveal that complexes 1 and 2 are antiferromagnetically coupled through azido bridges (J= -12.18 +/- 0.09 and -4.43 +/- 0.1 cm(-1) for 1 and 2, respectively). Complex 3 shows two different magnetic interactions through the two kinds of hydrogen bonds; one is antiferromagnetic (J(1) = - 9.69 +/- 0.03 cm(-1)) and the other is ferromagnetic (J(2) = 1.00 +/- 0.01 cm(-1)). From a magnetic point of view complex 4 is a ferromagnetic dinuclear complex (J= 1.91 +/- 0.01 cm(-1)) coupled through the EO bridge only. The coupling through the EE bridge is practically nil as the N(azido)-Cu-II (axial) distance (2.643 angstrom) is too long. (C) 2006 Elsevier Ltd. All rights reserved.

Syntheses and spectroscopy of diamine complexes of Zn(II) and Cd(II) ethylxanthates and the molecular structures of [M(S2COEt)(2)TMEDA]: formation of US nanoparticles from [Cd(S2COEt)(2)] and [Cd(S2COEt)(2)TMEDA]

The zinc and cadmium ethylxanthate complexes of N,N,N',N'-tetramethylethylenediamine (TMEDA), [M(S2COEt)(2)TMEDA], were synthesized and characterized with infrared, H-1 and C-13 NMR spectroscopy, mass spectrometry and X-ray crystallography. Whereas the cadmium complex has a six-coordinate {CdS4N2} centre with bidentate xanthate ligands, the zinc complex contains four coordinate {ZnS2N2} zinc with two monodentate xanthate groups. The cadmium species [Cd(S2COEt)(2)(diamine)] (where diamine = N,N-dimethylethylenediamine or N,N'-diisopropylethylenediamine) were also synthesized. The surfactant-assisted formation of nanoparticles from [Cd(S2COEt)(2)] and [Cd(S2COEt)(2)TMEDA] was studied with TEM, XRD and XRF techniques. From [Cd(S2COEt)(2)], spherical nanoparticle aggregates 140-200 nm in diameter were obtained but from [Cd(S2COEt)(2)TMEDA], single nanoparticles were produced with estimated diameters in the range of 4-7 nm and almost no aggregation. (C) 2004 Elsevier Ltd. All rights reserved.

Structure, and thermal, magnetic and chemical properties of copper(II)iodoacetate monohydrate

Reaction of iodoacetic acid with cupric carbonate in water in dimmed light yields green Cu(ICH2COO)(2 center dot)H2O (1). From X-ray crystallography, it is found to be a tetra-acetato bridged copper(II) dimer with the water molecules occupying the apical positions. In thermogravimetry, the coordinated water molecules are lost in the temperature range 50-100 degrees C. From magnetic susceptibility measurements in the temperature range 300-1.8 K, the exchange coupling constant J is found to be -142(1) cm(-1) and g = 2.18(2) with the spin Hamiltonian H = -2J{S-Cu1 center dot S-Cu2}. It reacts with 2,2'-bipyridine (bpy) to yield [Cu(bpy)(2)I]I. It oxidises thiophenol to Ph-S-S-Ph under dry N-2 atmosphere.

A hemiacetalate complex of Ru(II)

Reaction of cis-Ru(bisox)(2)Cl-2, where bisox is 4,4,4',4'-tetramethyl-2,2'-bisoxazoline, with excess of pyridine-2-carboxaldehyde (py-2-al) in 1:1 (v/v) methanol-water mixture under nitrogen atmosphere and subsequent addition of excess of NH4PF6 give [Ru(bisox)(2)(py-2-al)](PF6)(2)center dot H2O (1). Refluxing of 1 in dehydrated methanol in presence of triethylamine yields the corresponding hemiacetalate complex: [Ru(bisox)(2) (pyridine-2-(alpha-methoxymethanolato))] PF6 center dot 1.5H(2)O (2). Both the complexes have been characterised by single crystal X-ray crystallography, FTIR and NMR. In cyclic voltammetry in acetonitrile at a glassy carbon electrode, 2 displays a quasireversible Ru(II/III) couple at 1.08 V versus NHE which is not observed in 1. A tentative mechanism is proposed for the conversion of 1 to 2. DFT calculations with the LanL2DZ basis set have been performed to investigate these observations theoretically. (C) 2008 Elsevier B.V. All rights reserved.

Extraction behavior of nickel(II) using some of the BTBP-class ligands

Recently the BTBP-family of solvating ligands have been studied for their ability to separate trivalent actinides from lanthanides. Five of the BTBPs were evaluated for their ability to extract nickel(II) from aqueous nitrate media into cyclohexanone. It was shown by both solvent extraction and X-ray diffraction experiments that the BTBPs are capable of forming both 1: 1 and 1:2 complexes with nickel(II). When the BTBP concentration is low the nickel distribution ratio is governed by the formation of the nickel/BTBP complex while at higher BTBP concentrations the partitioning of the nickel complex between the two phases dictates the nickel distribution ratio.

Syntheses and crystal structures of two new coordination polymers of Cd(II) using organic spacer and inorganic-bridging ligands

Two new cadmium (II) complexes [Cd(hmt)(dca)(2)] (n) (1) and [Cd-3(hmt)(2)(SeCN)(6)(H2O)(2)] (n) (2) (hmt=hexamethylenetetramine, dca=dicyanamide) have been synthesized and characterized by X-ray single-crystal analysis. The complex 1 is a 2D rectangular grid of octahedral cadmium (II) with CdN6 chromophore where cadmium centers are doubly bridged by dicyanamide and hmt along a-axis, which are interlinked by dicyanamide running along c-axis. Whereas, complex 2 is a 1D chain of octahedral cadmium (II) with a three-leg ladder topology running along a-axis. The Cd(II) centers are doubly bridged through SeCN (infinite rail) along a-axis and singly bridged by hmt (two-step rung) along c-axis, having cadmium centers with CdSe2N3O and CdSe2N4 chromophores. The adjacent chains through H-bonding between coordinated water and hmt, and (SeSe)-Se-... interaction are extended to 2D supramolecular architecture.

Structural diversity in supramolecular architectures of Mn(II) through non-covalent interactions

Two mononuclear complexes of manganese(II), [Mn(OCN)(2)(phen)(2)] 1 and [Mn(NCO)(2)(bpy)(2)] 2 [1,10-phenanthroline (phen); 2,2'-bipyridine (bpy)], have been synthesized and characterized by single crystal X-ray analysis, infra-red spectroscopy and magnetic studies. The coordination structure of complex 2 is already reported. The cyanate anions are pendent in both the complexes. In 1, cyanate anion links manganese(II) through O-atom, whereas in 2 it coordinates through N-atom. The mononuclear fragments of 1 are built up to a supramolecular lamellar 3D architecture by pi-pi interactions only. On the other hand, mononuclear fragments of 2 are assembled to a 2D supramolecular brick-wall architecture by C-H-... pi interactions.

Synthesis and characterization of carbamoyl methyl pyrazole(CMPz) compounds of palladium(II) chloride: the crystal and molecular structure of [PdCl2{(C3H3N2CH2CONBu2)-Bu-i}(2)]

Carbamoyl methyl pyrazole compound of palladium(II) chloride of the type [PdCl2L2] (where L = C5H7N2CH2CON(C4H9)(2), C5H7N2CH2CON((C4H9)-C-i)(2), C3H3N2CH2CON(C4H9)(2), or C3H3N2CH2CON((C4H9)-C-i)(2)) has been synthesized and characterized by IR and H-1 NMR spectroscopy. The structure of the compound [PdCl2{(C3H3N2CH2CONBu2}2)-Bu-i] has been determined by single crystal X-ray diffraction and shows that the ligands are bonded through the soft pyrazolyl nitrogen atom to the palladium(II) chloride in a trans disposition. (c) 2007 Elsevier B.V. All rights reserved.

Syntheses of two new 1D and 3D networks of Cu(II) and Co(II) using malonate and urotropine as bridging ligands: Crystal structures and magnetic studies

Two new metal-organic based polymeric complexes, [Cu-4(O2CCH2CO2)(4)(L)].7H(2)O (1) and [CO2(O2CCH2CO2)(2)(L)].2H(2)O (2) [L = hexamethylenetetramine (urotropine)], have been synthesized and characterized by X-ray crystal structure determination and magnetic studies. Complex 1 is a 1D coordination polymer comprising a carboxylato, bridged Cu-4 moiety linked by a tetradentate bridging urotropine. Complex 2 is a 3D coordination polymer made of pseudo-two-dimensional layers of Co(II) ions linked by malonate anions in syn-anticonformation which are bridged by bidentate urotropine in trans fashion, Complex 1 crystallizes in the orthothombic system, space group Pmmn, with a = 14,80(2) Angstrom, b = 14.54(2) Angstrom, c = 7.325(10) Angstrom, beta = 90degrees, and Z = 4. Complex 2 crystallizes in the orthorhombic system, space group Imm2, a = 7.584(11) Angstrom, b = 15.80(2) Angstrom, c = 6.939(13) Angstrom, beta = 90.10degrees(1), and Z = 4. Variable temperature (300-2 K) magnetic behavior reveals the existence of ferro- and antiferromagnetic interactions in 1 and only antiferromagnetic interactions in 2. The best fitted parameters for complex 1 are J = 13.5 cm(-1), J = -18.1 cm(-1), and g = 2.14 considering only intra-Cu-4 interactions through carboxylate and urotropine pathways. In case of complex 2, the fit of the magnetic data considering intralayer interaction through carboxylate pathway as well as interlayer interaction via urotropine pathway gave no satisfactory result at this moment using any model known due to considerable orbital contribution of Co(II) ions to the magnetic moment and its complicated structure. Assuming isolated Co(II) ions (without any coupling, J = 0) the shape of the chi(M)T curve fits well with experimental data except at very low temperatures.