Lucia Soto

Synthesis, crystal structure, spectroscopic characterisation and magnetic properties of [Cu2(BIBM)2(C2O4)2]·4H2O (BIBM=bis(2-imidazolyl)bis(methoxycarbonyl)methylmethane)

Abstract The structure and spectroscopic and magnetic properties of bis(μ-1,2,3-oxalato)bis[bis(2-imidazolyl)bis(methoxycarbonyl)methylmethane]dicopper(II) tetrahydrate are described. The compound is built of centrosymmetric neutral dimeric [Cu2(BIBM)2(C2O4)2] entities linked through hydrogen bonds involving water molecules and oxalate groups. In the dimeric unit the two centrosymmetrically related copper — which are involved in CuN2O2O2′ chromophores lying in an elongated octahedral environment — are bridged through the oxalate group which acts in a bidentate–monodentate (μ-1,2,3) fashion. Both electronic and EPR spectra are indicative of an essentially dx2−y2 ground state for the copper(II) ions. Magnetic susceptibility measurements in the range 1.8–200 K show very weak antiferromagnetic exchange between the copper(II) ions (2J=−0.35 cm−1). This feature is discussed on the basis of the relative orientation of the coordination polyhedron around the metal atom and the bridging network.

Crystal and molecular structure and properties of the first characterized copper(II) one-dimensional polymer containing mepirizole [4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine]

The crystal and molecular structure of the complex [Cu(mpym)(H2O)(C4O4)]·2H2O [mpym = mepirizole = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine] has been determined by X-ray methods. It crystallizes in the orthorhombic space group Pbcn, with Z= 8, a= 18.592(3), b= 14.723(2) and c= 13.755(3)A, R= 0.053 and R′= 0.070 for 2697 reflections. The structure comprises infinite chains parallel to [001] built up of 1-bis(monodentate) squarate-O1O3 C4O4 anions bridging [Cu(mpym)(H2O)]2+ units. The copper(II) ions display distorted trigonal-bipyramidal geometry. Both electronic and ESR spectra are indicative of an essentially dz2 ground state for the CuII. No exchange coupling has been detected down to 4.2 K by means of magnetic susceptibility measurements. This feature is discussed on the basis of the relative orientation of the co-ordination polyhedron around the metallic atom and the bridging ligand.

Crystal structure, spectroscopic characterisation and magnetic properties of [Cu(BIP)(N3)]·H2O (BIP=3,3-bis(2-imidazolyl)propionate), a copper(II) polymeric compound with asymmetrical μ-1,3-azido bridges

Abstract The structure and the spectroscopic and magnetic properties of [3,3-bis(2-imidazolyl)propionato]azidocopper(II) monohydrate are described. The compound is built of [Cu(BIP)N3] entities which are connected through carboxylate groups from the BIP molecules —which act as a tridentate ligand—and asymmetrical μ-1,3-azido bridges, leading to a polymeric sheet-like structure. The copper atom is involved in a CuN3ON′ chromophore and lies in a distorted square-pyramidal environment. Both electronic and EPR spectra are indicative of an essentially dx2−y2 ground state for the copper(II) ions. Magnetic susceptibility measurements in the range 1.8–200 K show very weak antiferromagnetic exchange between the copper(II) ions (2J=−0.48 cm−1). This feature is discussed on the basis of the relative orientation of the coordination polyhedron around the metal atom and the bridging network.

Stereochemistry of [Cu(Tridentate Ligand)2] entities. crystal and molecular structure and electronic properties of [Cu(tedpa)2](PF6)2 (tedpa = N,N,N′N′-tetraethyl pyridinedicarboxamide)

Abstract The crystal and molecular structure of [Cu(tedpa) 2 ](PF 6 ) 2 have been determined by X-ray diffraction methods. The compound is built up of cationic [Cu(tedpa) 2 ] 2+ and PF 6 groups. The coordination geometry about the copper atom can be described as an elongated and strongly distorted octahedron (CuN 2 O 3 O′ chromophore). The EPR powder spectrum is slightly orthorhombic and from the g values and the partially resolved hyperfine components some covalency and molecular parameters have been estimated. EPR single crystal experiments indicate that the g -tensor axes follow the molecular bonds. Copyright

Crystal and molecular structure and electronic properties of [Cu(HBIP) (BIP) (ONO2)] (HBIP = 3,3-bis(2-imidazolyl)propionic acid)

Abstract The crystal and molecular structure of the complex [Cu(HBIP) (BIP)ONO2] (HBIP = 3,3-bis(2-imidazolyl)propionic acid) has been determined by X-ray methods. It crystallises in the monoclinic space group C2/c, Z=4, a=11.350(2), b=13.156(2), c=14.225(2) A , s=95.36(2)°, V=2114.8(6) A 3 . The CuN4O chromophore could be considered as an intermediate between the trigonal bipyramid (TBP) and square pyramid (SP). Neighbouring molecules of the complex are bound by very strong hydrogen bonds, as short as 2.478 A, between COO− and COOH groups. Electronic and EPR spectra are consistent with the crystallographic data.

Cobalt(II), nickel(II) and copper(II) complexes withN-cyano-N′-methyl-N″(2-[(5-methyl-1H-imidazol-4-yl)methylthio]ethyl)guanidine

SummaryN-Cyano-N′-methyl-N″(2-[(5-methyl-1H-imidazol-4-yl)-methylthio] ethyl) guanidine cimetidine (CM), complexes with CoII, NiII and CuII are described. The compounds are of stoichiometry [M(CM)2]SO4 · nH2O [M = CoII, NiII or CuII; n = 3,3 or 4, respectively], [M(CM)2](ClO4)2 [M = CoII or NiII], [M(CM)2]Cl2 · nH2O [M=CoII, NiII or CuII; n = 1, 2, or 2, respectively] and [Cu(CM)SO4] · 2H2O. The electronic spectra of the compounds in solid state, magnetic susceptibilities and i.r. and e.p.r. spectra were studied. Octahedral environments are proposed for the complexes: [M(CM)2]SO4·nH2O, [M(CM)2](ClO4)2, [Ni(CM)2]Cl2 · 2H2O, [Cu(CM)2]Cl2 · 2H2O and [Cu(CM)SO4] · 2H2O and a tetrahedral structure for [Co(CM)2]Cl2 · H2O.

Crystal and molecular structure of tris(mepirizole) copper(II) hexafluorophosphate [mepirizole = 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine

Abstract The X-ray crystal structure of Cu(mep)3(PF6)2 [mep = mepirizole or 4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6 methylpyrimidine], obtained from stoichiometric quantities of mep, Cu(NO3)2 and KPF6 in water/ethanol solution was determined. The trisbidentate Cu(mep)32+ cation is observed for the first time. One of the three mep molecules is disordered over two sets of positions related by crystallographic symmetry. The mep molecules exhibit two different conformations A and B: conformation B, which is observed for the first time, derives from the usual conformation A by rotating the pyrimidine ring by 180° around the central CN bond and rotating by 180° the methoxy group bonded to the pyrimidine ring. The copper atom lies at the centre of an elongated CuN6 octahedron; mean equatorial CuN distances: 2.05 A; axial CuN distances: 2.43 A.IR, electronic and EPR spectra are interpreted on the basis of the above stereochemistry.

Cimetidine complexes derived from cobalt(II), nickel(II) and copper(II) salts of polyatomic anions

SummaryCobalt(II), nickel(II) and copper(II) complexes [M(CM)2]X2 (X = BF4 or NO3) have been prepared with cimetidine (CM). Powder data, molar conductivities, magnetic moments, i.r. and electronic spectra support apseudo-octahedral stereochemistry with MN2N2⋆S2 chromophore and tentative structures are proposed for the complexes. Their properties are compared with these of previously prepared complexes.

Synthesis, properties and crystal structure of bis(metiamide)bis(isothiocyanato)nickel(II)

Abstract The crystal structure of Ni(metiamide)2(NCS)2 was determined by X-ray diffraction methods. Unlike cimetidine, which is a tridentate ligand, metiamide (C9H16N4S2): N-Methyl-N-[2-{(5-methylimidazol-4-yl)methylthio}ethyl]thiourea (which also possesses three potential donor sites) is bidentate, coordinated to the nickel atom through N(imidazole) and S(thioether) atoms. The S(thiourea) atom does not take part in the coordination; instead, the isothiocyanate ion is coordinated through nitrogen to the metal atom. The nickel atom lies on a centre of symmetry in an elongated octahedral environment: the nitrogen atoms occupy equatorial positions (NiN = 2.04 and 2.06 A) and S(thioether) atoms occupy apical positions (NiS = 2.58 A). Individual molecules are linked together by a unique S ⋯ HN hydrogen bond involving the uncoordinated S(thiourea) atom. IR, electronic reflectance and magnetic data are consistent with the structural results.

Pseudohalide derivatives of manganese(II) and copper(II) complexes with mepirizole, a biologically active pyrimidyl-pyrazole ligand

Abstract The synthesis and characterization of thiocyanate and azide derivatives of mepirizole(4-methoxy-2-(5-methoxy-3-methyl-pyrazol-1-yl)-6-methylpyrimidine, hereinafter L) with manganese(II) and copper(II) is reported. The compounds were characterized by IR, electronic and EPR spectra and analytical data. Spectroscopic results suggest the existence of dimeric neutral entities [L2Cu2(μ-X)2(X)2] (X = NCS or N3) with unsymmetrical end-to-end bridges and five-coordination geometry around the copper(II) ion. Magnetic susceptibility data show that in the azide derivative the copper atoms are antiferromagnetically coupled (J = −18 cm−1), but no magnetic exchange interaction could be detected in the thiocyanate compound up to 4.2 K. With regard to manganese(II) complexes (MnL2(NCS)2·2H2O and MnL(N3)2), an octahedral stereochemistry is proposed for the metal atom in both thiocyanate and azide derivatives, thus implying a polymeric structure in the second one.