A deliberate synthesis of a mononuclear trans-dimethoxide complex of ruthenium(III). X-ray crystal structure, electrochemistry and electron paramagnetic resonance

Using bis(3,5-dimethylpyrazol-1-yl) methane as the bidentate N donor ligand L, the yellow compound trans-[(RuL2)-L-III(OMe)(2)]ClO4 center dot CH2Cl2 is synthesized. It is a rare example of a mononuclear dialkoxo complex of Ru(III). It shows a quasireversible Ru(II/III) couple at -0.65 V versus NHE in acetonitrile at a Pt electrode. Its magnetic moment at room temperature corresponds to one unpaired electron. It displays a rhombic EPR spectrum in acetone at 77 K with g = 2.219, 2.062 and 1.855. (C) 2009 Elsevier B. V. All rights reserved.

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.

New bis(triazinyl) pyridines for selective extraction of americium(III)

New hydrophobic, tridentate nitrogen heterocyclic reagents (BATPs) such as 2,6-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl) pyridine (1) and 2,6-bis(9,9,10,10-tetramethyl-9,10-dihydro-1,2,4-triaza-anthrane-3-yl) pyridine (2) have been studied. I is resistant to hydrolysis in 3 M nitric acid, whereas 2 is resistant to both acid hydrolysis and radiolysis. The molecules are able to give significantly enhanced separations of americium(III) from an excess of europium(III) in nitric acid. Typically, for 1 D-Am = 500 and SFAm,/Eu = 5000 compared with D-Am = 30 and SFAm /Eu = 400 with the reference molecule 2,6-bis(isopropyl[1,2,4]triazin-3-yl) pyridine (7). In order to increase the stability of 1 and 2, the labile alpha-benzylic hydrogens that are present in 7 have been replaced by alkyl groups. Three molecules of 1 are able to enclose completely the coordination sphere of the M(III) in the crystal structure of [Y(1)(3)][Y(NO3)(5)]center dot NO3 center dot 2.5H(2)O.

Coordination and extraction studies of an unexplored bi-functional ligand, carbamoyl methyl pyrazole (CMPz) with uranium(VI), lanthanum(III) and cerium(III) nitrates

The bi-functional carbamoyl methyl pyrazole ligands, C5H7N2CH2CONBu2 (L-1), (C5H7N2CH2CONBu2)-Bu-i (L-2), C3H3N2CH2CONBu2 (L-3), (C3H3N2CH2CONBu2)-Bu-i (L-4) and C5H7N2CH2CON(C8H17)(2) (L-5) were synthesized and characterized by spectroscopic and elemental analysis methods. The selected coordination chemistry of L-1 to L-4 with [UO2(NO3)(2)center dot 6H(2)O], [La(NO3)(3)center dot 6H(2)O] and [Ce(NO3)(3)center dot 6H(2)O] has been evaluated. Structures for the compounds [UO2(NO3)(2) C5H7N2CH2CONBu2] (6) [UO2(NO3)(2) (C5H7N2CHCONBu2)-Bu-i] (7) and [Ce(NO3)(3){C(3)H(3)N(2)CH(2)CON(i)Bu2}(2)] (11) have been determined by single crystal X-ray diffraction methods. Preliminary extraction studies of the ligand L-5 with U(VI) and Pu(IV) in tracer level showed an appreciable extraction for U(VI) and Pu(TV) up to 10 M HNO3 but not for Am(III). Thermal studies of the compounds 6 and 7 in air revealed that the ligands can be destroyed completely on incineration. (c) 2007 Elsevier Ltd. All rights reserved.

A new cyano-bridged one-dimensional (GdFeIII)-Fe-III coordination polymer with o-phenanthroline as the blocking ligand: synthesis, structure, and magnetic properties

Synthesis, structural characterization, and magnetic properties of a new cyano-bridged one-dimensional iron (III)-gadolinium (III) compound, trans-[Gd(o-phen)(2)(H2O)(2)(mu-CN)(2)Fe(CN)(4)], - 2no-phen (o-phen = 1,10-phenanthroline), have been described. The compound crystallizes in the triclinic P (1) over bar space group with the following unit cell parameters: a = 10.538(14) angstrom, b = 12.004(14) angstrom, c = 20.61(2) angstrom, alpha = 92.41(1)degrees, beta = 92.76(1)degrees, gamma = 11 2.72(1)degrees, and Z = 2. In this complex, each gadolinium (III) is coordinated to two nitrile nitrogens of the CN groups coming from two different ferricyanides, the mutually trans cyanides of each of which links another different Gd-III to create -NC-Fe(CN)(4)-CN-Gd-NC- type 1-D chain structure. The one-dimensional chains are self-assembled in two-dimensions via weak C-H center dot center dot center dot N hydrogen bonds. Both the variable-temperature (2-300 K, 0.01 T and 0.8 T) and variable-field (0-50 000 Gauss, 2 K) magnetic measurements reveal the existence of very weak interaction in this molecule. The temperature dependence of the susceptibilities has been analyzed using a model for a chain of alternating classic (7/2) and quantum (1/2) spins. (c) 2005 Elsevier B.V. All rights reserved.

Methylammonium antimony sulfide

Bis(methylammonium) octaantimony(III) dodecasulfide persulfide, (CH3NH3)(2)[Sb8S12(S-2)], contains pairs of [Sb4S7](2-) chains joined through an unusual persulfide bond to create infinite double [Sb8S14](2-) chains. The double chains are interlocked by longer Sb center dot center dot center dot S interactions to form sheets approximately parallel to the (101) crystallographic plane. Methylammonium cations, formed by decomposition of 2-methylpropane-1,2-diamine during the synthesis, are located in large (Sb8S10) hetero-ring apertures created within the double chains.

The synthesis and characterisation of four new antimony sulphides incorporating transition-metal complexes

Four new antimony sulphides, [T(dien)(2)]Sb6S10 center dot xH(2)O [T = Ni (1), Co (2) x approximate to 0.45], [Co(en)(3)]SbsSI(3) (3) and [Ni(en)(3)]Sb12S19 (4), have been synthesised under solvothermal conditions. In compounds (1) - (3), Sb12S228- secondary building units are connected to form layered structures. In (1) and (2), Sb-6 S-2- layers containing Sb16S16 heterorings are separated by [T(dien]2](2+) cations, whilst in (3), Sb8 S2- layers 10 13 contain [Co(en)3]2+ cations within large Sb22S22 pores. Compound (4) adopts a three-dimensional structure in which [Ni(en)3 12 cations lie within ca. 5 A wide channels. (c) 2007 Elsevier Ltd. All rights reserved.

Syntheses, crystal structures and magnetic properties of carboxylato-bridged polymeric networks of Mn-II

Three new carboxylato-bridged polymeric networks of Mn-II having molecular formula [Mn(ox)(dpyo)](n) (1), {[Mn-2(mal)(2)(bpee)(H2O)(2)]center dot 0.5(bpee)center dot 0.5(CH3OH)}n, (2) and {[Mn-3(btc)(2)(2,2'-bipy)(2)(H2O)(6)]center dot 4H(2)O}(n) (3) [dpyo, 4,4'-bipyridine N,N'dioxide; bpee, trans-1,2 bis(4-pyridyl) ethylene; 2,2'-bipy, 2,2'-bipyridine; ox = oxalate dianion; mal = malonate dianion; btc = 1,3,5-benzenetricarboxylate trianion] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structure determination of complex I reveals a covalent bonded 2D network containing bischelating oxalate and bridging dpyo; complex 2 is a covalent,bonded 3D polymeric architecture, formed by bridging malonate and bpee ligands, resulting in an open framework with channels filled by uncoordinated disordered bpee and methanol molecules. Whereas complex 3, comprising btc anions bound to three metal centers, is a 1D chain which further extends its dimensionality to 3D via pi-pi and H-bonding interactions. Low temperature magnetic measurements reveal the existence of weak antiferromagnetic interaction in all these complexes. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).

Synthesis, structure and properties of cobalt(II/III) seleno-bisphenolate complexes containing NN bidentate co-ligands: kinetic studies on the reduction of a cobalt(III) complex by ascorbic acid in 80% MeCN-20% water

Two cobalt complexes, [Co(L-Se)(phen)]center dot CH2Cl2 (1) and [Co(L-Se)(N,N-Me(2)en)(CH3COO-)] (2) have been synthesized and characterized by elemental analyses, magnetic measurements, i.r. studies etc. Single crystal X- ray studies reveal that in complex (1) cobalt atom is in +2 oxidation state with trigonal bipyramidal geometry, while in complex (2) it is in +3 oxidation state and surrounded octahedrally. The asymmetric unit of complex (2) contains two crystallographically independent discrete molecules. Complex (1) was found to be paramagnetic with mu(eff) = 2.19 BM indicating a low spin cobalt(II) d(7) system, whereas complex (2) is found to be diamagnetic with cobalt(III) in low spin d(6) state. The kinetic studies on the reduction of (2) by ascorbic acid in 80% MeCN-20% H2O (v/v) at 25 degrees C reveal that the reaction proceeds through the rapid formation of inner-sphere adduct, probably by replacing the loosely coordinated AcO- group, followed by electron transfer in a slow step and is supported by a large Q (formation constant) value.

Tuning of redox potential and visible absorption band of ruthenium(II) complexes of (benzimidazolyl) derivatives: synthesis, characterization, spectroscopic and redox properties, X-ray structures and DFT calculations

Six ruthenium(II) complexes have been prepared using the tridentate ligands 2,6-bis(benzimidazolyl) pyridine and bis(2-benzimidazolyl methyl) amine and having 2,2'-bipyridine, 2,2':6',2 ''-terpyridine, PPh3, MeCN and chloride as coligands. The crystal structures of three of the complexes trans-[Ru(bbpH(2))(PPh3)(2)(CH3CN)I(ClO4)(2) center dot 2H(2)O (2), [Ru(bbpH(2))(bpy)Cl]ClO4 (3) and [Ru(bbpH(2))(terpy)](ClO4)(2) (4) are also reported. The complexes show visible region absorption at 402-517 nm, indicating that it is possible to tune the visible region absorption by varying the ancillary ligand. Luminescence behavior of the complexes has been studied both at RT and at liquid nitrogen temperature (LNT). Luminescence of the complexes is found to be insensitive to the presence of dioxygen. Two of the complexes [Ru(bbpH(2))(bpy)Cl]ClO4 (3) and [Ru(bbpH(2))(terpy]ClO4)(2) (4) show RT emission in the NIR region, having lifetime, quantum yield and radiative constant values suitable for their application as NIR emitter in the solid state devices. The DFT calculations on these two complexes indicate that the metal t(2g) electrons are appreciably delocalized over the ligand backbone. (C) 2006 Elsevier B.V. All rights reserved.

Structural variations in Ni(II) complexes of salen type di-Schiff base ligands

Three di-Schiff-base ligands, N,N'-bis(salicylidene)-1,3-propanediamine (H(2)Salpn), N,N'-bis(salicylidene)-1,3-pentanedianiine (H(2)Salpen) and N,N'-bis(salicylidine)-ethylenediamine (H(2)Salen) react with Ni(SCN)(2). 4H(2)O in 2:3 molar ratios to form the complexes; mononuclear [Ni(HSalpn)(NCS)(H2O)]center dot H2O (1a), trinuclear [{Ni(Salpen)}(2)Ni(NCS)(2)] (2b) and trinuclear [{Ni(Salen)}(2)Ni(NCS)(2)] (3) respectively. All the complexes have been characterized by elemental analyses, IR and UV-VIS spectra, and room temperature magnetic susceptibility measurements. The structures of la and 2b have been confirmed by X-ray single crystal analysis. In complex la, the Ni(II) atom is coordinated equatorially by the tetradentate, mononegative Schiff-base, HSalpn. Axial coordination of isothiocyanate group and a water molecule completes its octahedral geometry. The hydrogen atom attached to one of the oxygen atoms of the Schiff base is involved in a very strong hydrogen bond with a neighboring unit to form a centrosymmetric dimer. In 2b, two square planar [Ni(Salpen)] units act as bide mate oxygen donor ligands to a central Ni(II) which is also coordinated by two mutually cis N-bonded thiocyanate ligands to complete its distorted octahedral geometry. Complex 3 possesses a similar structure to that of 2b. A dehydrated form of la and a hydrated form of 2b have been obtained and characterized. The importance of electronic and steric factors in the variation of the structures is discussed. (c) 2007 Elsevier Ltd. All rights reserved.

Influence of counter anions on the structures and magnetic properties of trinuclear Cu(II) complexes containing a mu(3)-OH core and Schiff base ligands

Four trinuclear Cu(II) complexes, [(CuL1)(3)(mu(3)-OH)](NO3)(2) (1), [(CuL2)(3)(mu(3)-OH)](I)(2)center dot H2O (2), [(CuL3)(3)(mu(3)-OH)](I)(2) (3) and [(CuL1)(3)(mu(3)-OH)][(CuI3)-I-1] (4), where HL1 (8-amino-4-methyl-5-azaoct-3-en-2-one), HL2 [7-amino-4-methyl-5-azaoct-3-en-2-one] and HL3 [7-amino-4-methyl-5-azahept-3-en-2- one] are the three tridentate Schiff bases, have been synthesized and structurally characterized by X-ray crystallography. All four complexes contain a partial cubane core, [(CuL)(3)(mu(3)-OH)](2+) in which the three [CuL] subunits are interconnected through two types of oxygen bridges afforded by the oxygen atoms of the ligands and the central OH- group. The copper(II) ions are in a distorted square-pyramidal environment. The equatorial plane consists of the bridging oxygen of the central OH- group together with three atoms (N, N, O) from the Schiff base. The oxygen atom of the Schiff base also coordinates to the axial position of Cu(II) of another subunit to form the cyclic trimer. Magnetic susceptibilities have been determined for these complexes over the temperature range of 2-300 K. The isotropic Hamiltonian, H = -J(12)S(1)S(2) - J(13)S(1)S(3) - J(23)S(2)S(3) has been used to interpret the magnetic data. The best fit parameters obtained are: J = - 54.98 cm(-1) g = 2.24 for 1; J = - 56.66 cm(-1), g = 2.19 for 2; J = -44.39 cm(-1), g = 2.16 for 3; J = - 89.92 cm(-1), g = 2.25 for 4. The EPR data at low temperature indicate that the phenomenon of spin frustration occurs for complexes 1-3. (c) 2007 Elsevier B.V. All rights reserved.

Coordination-driven self-assembly of a novel carbonato-bridged heteromolecular neutral nickel(II) triangle by atmospheric CO2 fixation

Formation of a quasi-symmetrical mu(3)-carbonato-bridged self-assembled heteromolecular triangle of Ni(II), [(mu(3)-CO3){Ni-2(salmeNH)(2)(NCS)(2)}[Ni(salmeNH(2))(2)]center dot Et2O center dot H2O (HsalmeNH = 2-[(3-methylamino-propylimino)-methyl]-phenol) involves atmospheric CO2 uptake in a neutral medium, by spontaneous self-reorganization of the starting mononuclear Ni(II)-Schiff-base complex, [Ni(salmeNH)(2)]. The environment around Ni(II) in two of the subunits is different from the third one. The starting complex, (Ni(salmeNH)(2)], and one of the possible intermediate species, [Ni(salmeNH(2))(2)(NCS)(2)], which has a very similar coordination environment to that in the third Ni(II) center, have been characterized structurally. A plausible mechanism for the formation of such a triangle has also been proposed. The compound shows a very strong antiferromagnetic coupling. Fit as a regular triangular arrangement gave J = -53.1, g = 2.24, and R = 1.5 x 10(-4).

Anion-directed template synthesis and hydrolysis of mono-condensed Schiff base of 1,3-pentanediamine and o-hydroxyacetophenone in Ni-II and Cu-II complexes

Bis(o-hydroxyacetophenone)nickel(II) dihydrate, on reaction with 1,3-pentanediamine, yields a bis-chelate complex [NiL2]center dot 2H(2)O (1) of mono-condensed tridentate Schiff base ligand HL {2-[1-(3-aminopentylimino)ethyl]phenol}. The Schiff base has been freed from the complex by precipitating the Nil, as a dimethylglyoximato complex. HL reacts smoothly with Ni(SCN)(2)center dot 4H(2)O furnishing the complex [NiL(NCS)] (2) and with CuCl2 center dot 2H(2)O in the presence of NaN3 or NH4SCN producing [CuL(N-3)](2) (3) or [CuL(NCS)] (4). On the other hand, upon reaction with Cu(ClO4)(2)center dot 6H(2)O and Cu(NO3)(2)center dot 3H(2)O, the Schiff base undergoes hydrolysis to yield ternary complexes [Cu(hap)(pn)(H2O)]ClO4 (5) and [Cu(hap)(pn)(H2O)]NO3 (6), respectively (Hhap = o-hydroxyacetophenone and pn = 1,3-pentanediamine). The ligand HL undergoes hydrolysis also on reaction with Ni(ClO4)(2)center dot 6H(2)O or Ni(NO3)(2)center dot 6H(2)O to yield [Ni(hap)(2)] (7). The structures of the complexes 2, 3, 5, 6, and 7 have been confirmed by single-crystal X-ray analysis. In complex 2, Ni-II possesses square-planar geometry, being coordinated by the tridentate mono-negative Schiff base, L and the isothiocyanate group. The coordination environment around Cu-II in complex 3 is very similar to that in complex 2 but here two units are joined together by end-on, axial-equatorial azide bridges to result in a dimer in which the geometry around Cu-II is square pyramidal. In both 5 and 6, the Cu-II atoms display the square-pyramidal environment; the equatorial sites being coordinated by the two amine groups of 1,3-pentanediamine and two oxygen atoms of o-hydroxyacetophenone. The axial site is coordinated by a water molecule. Complex 7 is a square-planar complex with the Ni atom bonded to four oxygen atoms from two hap moieties. The mononuclear units of 2 and dinuclear units of 3 are linked by strong hydrogen bonds to form a one-dimensional network. The mononuclear units of 5 and 6 are joined together to form a dimer by very strong hydrogen bonds through the coordinated water molecule. These dimers are further involved in hydrogen bonding with the respective counteranions to form 2-D net-like open frameworks. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

Solvent-Assisted Formation of Vesicles by a Self-Assembling Ni-3-Schiff Base Complex

A linear trinuclear Ni-Schiff base complex [Ni-3(salpen)(2)(PhCH2COO)(2)(EtOH)] has been synthesized by combining Ni(ClO4)(2)center dot 6H(2)O, phenyl acetic acid (C6H5CH2COOH), and the Schiff base ligand, N,N'-bis(salicylidene)-1,3-pentanediamine (H(2)salpen). This complex is self-assembled through hydrogen bonding and C-H-g interaction in the solid state to generate a sheet-like architecture, while in organic solvent (CH2Cl2), it forms vesicles with a mean diameter of 290 nm and fused vesicles, depending upon the concentration of the solution. These vesicles act as an excellent carrier of dye molecules in CH2Cl2. The morphology of the complex has been determined by scanning electron microscopy and transmission electron microscopy experiments, and the encapsulation of dye has been examined by confocal microscopic image and electronic absorption spectra.