Showing papers on "Octahedral molecular geometry published in 2002"
TL;DR: Two new lead(II) phosphonates, namely, Pb2[PMIDA]*1.5H2O and Pb(H2L) (2), have been synthesized by hydrothermal reactions at 150 degrees C, resulting in a 3D network with micropores, whose cavity is filled by lattice water molecules interlinked via hydrogen bonds.
Abstract: Two new lead(II) phosphonates, namely, Pb2[PMIDA]*1.5H2O (1) (H4PMIDA = H2O3PCH2N(CH2CO2H)2) and Pb(H2L) (2) (H4L = CH3N(CH2PO3H2)2), have been synthesized by hydrothermal reactions at 150 degrees C. Complex 1 crystallized in tetragonal P42/n with cell dimensions of a = 17.317(7) and c = 7.507(5) A and Z = 8. In complex 1, Pb(1) is 6-coordinated by chelation in a tetradentate fashion by a PMIDA ligand (3 O, 1 N) and two phosphonate oxygen atoms from neighboring Pb(PMIDA) units in a severely distorted octahedral geometry, whereas Pb(2) is 6-coordinated by 4 carboxylate and 2 phosphonate oxygen atoms also with a severely distorted octahedral environment. These two different types of Pb(II) ions are interconnected through bridging carboxylate and phosphonate groups, resulting in a 3D network with micropores, whose cavity is filled by lattice water molecules interlinked via hydrogen bonds. Each PMIDA ligand bridges with 8 Pb(II) ions (3 Pb(1) and 5 Pb(2)). Complex 2 is orthorhombic, P2(1)2(1)2(1), with a = 7.382(5), b = 7.440(6), and c = 30.75(2) A and Z = 8. The structure of 2 features a 2D double lead(II) phosphonate layer along the ab plane. Each lead(II) ion is 5-coordinated by five phosphonate oxygen atoms from four ligands in a distorted trigonal bipyramid geometry. These double layers are further interconnected via hydrogen bonds between the protonated and uncoordinated phosphonate oxygens along the c-axis.
132 citations
TL;DR: Reaction of N,N'-bis(phosphonomethyl)-1,10-diaza-18-crown-6 (H(4)L) with copper(II) acetate in 1:1 ethanol/water mixed solvents afforded a new crystal-engineered supramolecular metal phosphonate, Cu(H(2)L), which is described as Jahn-Teller-distorted octahedral.
Abstract: Reaction of N,N'-bis(phosphonomethyl)-1,10-diaza-18-crown-6 (H(4)L) with copper(II) acetate in 1:1 ethanol/water mixed solvents afforded a new crystal-engineered supramolecular metal phosphonate, Cu(H(2)L) (complex 1). By reaction of the same ligand with cadmium(II) nitrate in a 2:1 (M/L) ratio in methanol, a cadmium(II) complex with a 3D network structure was isolated, Cd(2.75)(L)(H(2)O)(7) x 1.5NO(3) x 7H(2)O x MeOH (complex 2). The copper(II) complex crystallized in the monoclinic space group P2(1)/c, with a =10.125(4), b = 14.103(6), and c = 14.537(6) A, beta = 91.049(8) degrees, V = 2075.4(16) A(3), and Z = 2. The Cu(II) ions in complex 1 are 6-coordinated by two phosphonate oxygen atoms, two nitrogen, and two oxygen atoms from the crown ether ring. Their coordination geometry can be described as Jahn-Teller-distorted octahedral, with elongated Cu-O(crown) distances (2.634(4) and 2.671(4) A for Cu(1) and Cu(2), respectively). The other two crown oxygen atoms remain uncoordinated. Neighboring two Cu(H(2)L) units are further interlinked via a pair of strong hydrogen bonds between uncoordinated phosphonate oxygen atoms, resulting in a one-dimensional supramolecular array along the a axis. The cadmium(II) complex is tetragonal, P4(2)/n (No. 86) with a = 20.8150(9) and c = 18.5846(12) A, V = 8052.0(7) A(3), and Z = 8. Among four cadmium(II) atoms in an asymmetric unit, one is 8-coordinated by four chelating phosphonate groups, the second one is 8-coordinated by 6 coordination atoms from a crown ring and two oxygen atoms from two phosphonate groups, the third Cd(II) atom is octahedrally coordinated by three aqua ligands and three phosphonate oxygen atoms from three phosphonate groups, and the fourth one is 6-coordinated by four aqua ligands and two oxygen atoms from two phosphonate groups in a distorted octahedral geometry. These cadmium atoms are interconnected by bridging phosphonate tetrahedra in such a way as to form large channels along the c direction, in which the lattice water molecules, methanol solvent, and nitrate anions reside. The effect of extent of deprotonation of phosphonic acids on the type of complex formed is also discussed.
85 citations
TL;DR: In this paper, an octahedral geometry for the CrIII, MnII and CoII, square planar geometry for NiII and PdII and tetragonal geometry for CuII complexes are presented.
Abstract: CrIII, MnII, CoII, NiII, CuII and PdII complexes of the macrocyclic ligand, 2,3,5,8,9,11 hexamethyl-1,4,7,10 tetraaza- cyclododeca-1,3,7,9 tetraene (DADAP), have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, i.r., electronic and e.p.r. spectral studies. These spectral studies suggest an octahedral geometry for the CrIII, MnII and CoII, square planar geometry for NiII and PdII and tetragonal geometry for CuII complexes.
83 citations
TL;DR: In this article, two α-diimine vanadium complexes were synthesized by ligand exchange reaction of VCl3(THF)3 with the appropriate α diimine ligand, and the chemical structure of 1 was determined by X-ray crystallography and found to consist of a vanadium atom in a distorted octahedral geometry with the oxygen atom of the coordinated THF, two nitrogen atoms of the diimines ligand and one chlorine atom in the same plane.
Abstract: Two novel α-diimine vanadium complexes, [PhNC(Me)–C(Me)NPh]V(THF)Cl3 (1) and {[2,6-(i-Pr)2Ph]NCH–CHN[2,6-(i-Pr)2Ph]}VCl3 (2) were synthesized by ligand exchange reaction of VCl3(THF)3 with the appropriate α-diimine ligand. The chemical structure of 1 was determined by X-ray crystallography and found to consist of a vanadium atom in a distorted octahedral geometry with the oxygen atom of the coordinated THF, two nitrogen atoms of the diimine ligand and one chlorine atom in the same plane. Complexes 1 and 2 were characterized by FT-IR, 1H NMR, elemental analysis and 2 was identified as the THF
free V(III) diimine complex. The behavior of 1 and 2 as ethylene polymerisation catalysts was preliminarily explored after activation with MAO or AlEt2Cl and compared with that of {2,6-bis[2,6-(i-Pr)2PhNC(Me)]2(C5H3N)}VCl3 (3) under similar conditions. Upon activation of 1–3 with AlEt2Cl, moderate polymerisation activities were observed at −40 °C whereas the corresponding MAO activated catalysts exhibit lower activity. The molar concentration of the active sites at −40 °C is rather low (found in the range 5–12% of total vanadium) and results from slow alkylation of the complexes followed by reduction of V(III) catalysts to inactive V(II) species. At
50 °C an increase of the ethylene polymerisation activities of the 1–3-AlEt2Cl catalysts was observed and the trend of the productivity values follows the steric hindrance at the metal center. Alkylation of the diimine ligands of the 1–3 catalysts with AlEt2Cl producing deactivation of the active sites is only partially active under polymerisation conditions whereas the reaction of 1 and 2 with MAO produces fast degradation of the active species.
75 citations
TL;DR: Two new dicyanamide bridged complexes, [Cu(μ1,5dca)2(phen)]n (1) and [Cd(μ 1,5-dca)-2(py)2]n (2) have been synthesized and their structures have been determined by X-ray crystallography diffraction as discussed by the authors.
70 citations
TL;DR: Two heterodimetallic complexes of formulae have been synthesized and characterized and a quantitative evaluation of the J(Co,Gd) ferromagnetic interaction parameter was allowed for the first time.
Abstract: Two heterodimetallic complexes of formulae [LCo(MeOH)Gd (NO3)3] (1) and [LCo(AcO)2Gd(NO3)2] (2) (H2L = 1,3-bis[(3-methoxysalicylidene)amino]-2,2'-dimethylpropane) have been synthesized and characterized. The structure of 1 consists of discrete dinuclear entities. The cobalt(II) ion exhibits a square-pyramidal geometry, in which the basal plane is formed by the N2O2 set of the inner Schiff base site and the apical position is occupied by the methanol oxygen atom. The gadolinium(III) ion is ten-coordinate to three bidentate nitrate groups and the four oxygen atoms of the Schiff base. The phenolate oxygen atoms act as a bridge between both metal ions. Complex 2 is also formed by isolated dinuclear species. The cobalt(III) ion shows a distorted octahedral geometry in which the equatorial plane is formed by the N2O2 set of the Schiff base, and the axial positions are occupied by two oxygen atoms from both acetate groups. The gadolinium(III) ion is ten-coordinate to two bidentate nitrate groups, two oxygen atoms of the acetate groups, and the four oxygen atoms of the Schiff base. The metal ions are bridged through both the phenolate oxygen and the acetate groups, the latter acting as mu 2 ligands. Magnetic measurements on compound 1 allowed, for the first time, a quantitative evaluation of the J(Co,Gd) ferromagnetic interaction parameter (J = 0.90 cm-1). The CoII zero-field splitting has to be taken into account to fit the experimental data at low temperature (D = 4.2 cm-1). In complex 2, the magnetically isolated gadolinium center obeys a Curie law.
68 citations
TL;DR: The series of transition metal complexes derived from the pentadentate ligand PY5, 2,6-(bis-2-pyridyl)methoxymethane)pyridine, illustrates the intrinsic propensity of this ligand to complex metal ions and shows the high-spin nature of the complexes and the anticipated stabilization of the divalent oxidation state.
Abstract: A series of transition metal complexes derived from the pentadentate ligand PY5, 2,6-(bis-(bis-2-pyridyl)-methoxymethane)pyridine, illustrates the intrinsic propensity of this ligand to complex metal ions. X-ray structural data are provided for six complexes (1-6) with cations of the general formula [M I I (PY5)(Cl)] + , where M = Mn, Fe, Co, Ni, Cu, Zn. In complexes 1-4 and 6, the metal ions are coordinated in a distorted-octahedral fashion; the four terminal pyridines of PY5 occupy the equatorial sites while the axial positions are occupied by the bridging pyridine of PY5 and a chloride anion. Major distortions from an ideal octahedral geometry arise from displacement of the metal atom from the equatorial plane toward the chloride ligand and from differences in pyridine-metal-pyridine bond angles. The series of complexes shows that M(II) ions are consistently accommodated in the ligand by displacement of the metal ion from the PY5 pocket, a tilting of the axial pyridine subunit, and nonsymmetrical pyridine subunit ligation in the equatorial plane. The displacement from the ligand pocket increases with the ionic radius of M(II). The axial pyridine tilt, however, is approximately the same for all complexes and appears to be independent of the electronic ground state of M(II). In complex 5, the Cu(II) ion is coordinated by only four of the five pyridine subunits of the ligand, resulting in a square-pyramidal complex. The overall structural similarity of 5 with the other complexes reflects the strong tendency of PY5 to enforce a distorted-octahedral coordination geometry. Complexes 1-6 are further characterized in terms of solution magnetic susceptibility, electrochemical behavior, and optical properties. These show the high-spin nature of the complexes and the anticipated stabilization of the divalent oxidation state.
67 citations
TL;DR: In this article, a μ-alkoxo-bridged dinuclear complex of a binucleating bis-pyridyl ligand was constructed in the presence of a two-fold metal excess.
Abstract: Crystal structures, solution properties and ribonuclease activity of copper(II) complexes of a binucleating, bis-pyridyl ligand (N,N′-bis(2-pyridylmethyl)-1,3-diaminopropan-2-ol, L) have been investigated. The single-crystal X-ray structure of the mononuclear complex [CuL(ClO4)2] (1) shows distorted octahedral geometry around the metal ion, with the four nitrogens of the ligand in the equatorial plane of copper(II). A μ-alkoxo-bridged dinuclear complex is formed in the presence of a two-fold metal excess. Despite the symmetrical ligand, the two metal ions in [Cu2(LH−1)(DPP)(ClO4)(CH3OH)]ClO4 (2, DPP = diphenyl phosphate) have distinct, distorted octahedral (Cu1) and square pyramidal (Cu2) geometry. Beside the alkoxo-oxygen, the phosphate
group of DPP also bridges the two metal centers in 2 in a μ-1,3-bridging mode. The complexes formed in aqueous solution are likely to have analogous structures to 1 and 2. The dinuclear [Cu2(LH−1)(OH)] complex efficiently promotes the hydrolysis/transesterification of both activated (2-hydroxypropyl p-nitrophenyl phosphate, hpnp) and non-activated, biological phosphodiesters (uridine-2′,3′-cyclic-monophosphate, cUMP and uridylyl-(3′,5′)-uridine, UpU). For example, a 2 mM solution of the dinuclear complex provides 5 orders of magnitude acceleration in the hydrolysis of cUMP. The proposed mechanisms include double Lewis-acid activation with intramolecular general base catalysis.
67 citations
TL;DR: Density functional calculations have been used to investigate oxygen atom transfer reactions from the biological oxygen atom donors trimethylamine N-oxide and dimethyl sulfoxide to the molybdenum(IV) complexes, indicating that the former is energetically unfavorable while the latter was found to be favorable.
Abstract: Density functional calculations have been used to investigate oxygen atom transfer reactions from the biological oxygen atom donors trimethylamine N-oxide (Me3NO) and dimethyl sulfoxide (DMSO) to the molybdenum(IV) complexes [MoO(mnt)(2)](2-) and [Mo(OCH3)(mnt)(2)](-) (mnt = maleonitrile-1,2-dithiolate), which may serve as models for mononuclear molybdenum enzymes of the DMSO reductase family. The reaction between [MoO(mnt)(2)](2-) and trimethylamine N-oxide was found to have an activation energy of 72 kJ/mol and proceed via a transition state (TS) with distorted octahedral geometry, where the MOO is bound through the oxygen to the molybdenum atom and the N-O bond is considerably weakened. The computational modeling of the reactions between dimethyl sulfoxide (DMSO) and [MoO(mnt)(2)](2-) or [Mo(OCH3)(mnt)(2)](-) indicated that the former is energetically unfavorable while the latter was found to be favorable. The addition of a methyl group to [MoO(mnt)(2)](2-) to form the corresponding des-oxo complex not only lowers the relative energy of the products but also lowers the activation energy. In addition, the reaction with [Mo(OCH3)(mnt)(2)](-) proceeds via a TS with trigonal prismatic geometry instead of the distorted octahedral TS geometry modeled for the reaction between [MoO(mnt)(2)](2-) and Me3NO.
64 citations
TL;DR: In this article, a quadridentate, N2O2-type Schiff base, synthesised from 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one (4-aminoantipyrine) and benzil, forms stable complexes with transition metal ions such as Cu(II), Ni(II) and VO(IV) in ethanol.
Abstract: A novel quadridentate, N2O2-type Schiff base, synthesised from 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one (4-aminoantipyrine) and benzil, forms stable complexes with transition metal ions such as Cu(II), Ni(II), Co(II), Mn(II), Zn(II) and VO(IV) in ethanol. Microanalytical data, magnetic susceptibility, IR, UV-Vis., 1H NMR, ESR and mass spectral techniques were used to confirm the structures. Electronic absorption and IR spectra of the complexes suggest an octahedral geometry around the central metal ion, except for the VO(IV)complex which has a square pyramidal geometry. The non-electrolytic behaviour of the chelates was assessed from the low conductance data, except for the vanadyl complex and the dipyridinyl adducts of the copper complexes which show a higher conductance, supporting an electrolytic nature of these complexes. The monomeric nature of the chelates was confirmed by their magnetic susceptibility values. Cyclic voltammograms of the [CuLCl2] and [CuL(OAc)2] complexes in DMSO solution...
57 citations
TL;DR: In this paper, a single-crystal X-ray diffraction was performed to study structural changes with changing chemical composition in the octahedral sheet of 1 M micas.
Abstract: To study structural changes with changing chemical composition in the octahedral sheet of trioctahedral potassium-rich 1 M micas, 3 natural and 12 synthetic micas were examined by single-crystal X-ray diffraction. Samples with Ni2+, Mg2+, Co2+, Fe2+, and Al3+ in the octahedral sheet and with Si4+, Al3+ and one sample with Ga3+ in the tetrahedral sheet were prepared at high temperatures and pressures, which yielded crystallites ≤200 μm in size. For samples with approximately AlSi3 composition of the tetrahedral sheet and with no octahedral Al3+, mean M1-O and M2-O octahedral bond lengths correlate very well with the mean ionic radius of the octahedral cations. For these samples, the M1 and M2 sites are found to be very similar or identical within experimental error in terms of mean M-O bond lengths, bond angles, and polyhedral distortion parameters. Octahedral distortion is negatively correlated with the size of the octahedral cation. Octahedra in Ni2+-mica show the largest deviation from ideal octahedral geometry, whereas those in annite are closest to ideal octahedral geometry, but they are still significantly flattened. Octahedral Al3+ prefers the M2 site. This causes the mean M1-O bond length to decrease less with increasing Al3+ content as compared to the mean M2-O distance. This Al3+ preference for M2 also causes the M2 site to become smaller and more distorted than the M1 site. Refinement of the Mg-Fe ratios in the octahedral sites along the annite-phlogopite join shows that the two cations are statistically distributed over M1 and M2. Tetrahedra are regular and show only a small elongation along c * . Tetrahedral distortion parameters for the AlSi3 micas show no correlation with chemistry of the octahedral layer. However, the mean T-O bond lengths increase slightly with increasing size of the octahedral cation. With decreasing size of the lateral dimension of the octahedral sheet in the (001) plane, the tetrahedral sheet shows increasing ditrigonal distortion. Largest tetrahedral rotation angles are observed for synthetic near end-member siderophyllite with α = 11.5° and for tetra-gallium-phlogopite KMg3GaSi3O10(OH)2 with α = 10.8°.
TL;DR: In this paper, two coordination polymeric complexes [Co(pzca) 2 (H 2 O)] n ( 1 ) and [Mn(pza) 2 ] n ( 2 ) (pzCA=2-pyrazinecarboxylate) have been synthesized by a hydrothermal reaction of M(CH 3 COO) 2 ·4 H 2 O (M=Co, Mn) and 2-Pyrazine carboxylic acid.
29 Oct 2002
TL;DR: Chromium(II) and chromium(III) complexes bearing two bulky monoanionic N,N-chelating pyrrolide-imine ligands, {ArNCH(C4H3N-2)}2Cr(µ-Cl)2Li(THF)2======(2), have been prepared in high yield by treatment of the sodium and lithium salts of ArNCH, C4H 3NH-2, and C6H 3N-3N with CrCl2(thF) and CrCl3(TH
Abstract: Chromium(II) and chromium(III) complexes bearing two bulky monoanionic N,N-chelating pyrrolide-imine ligands, {ArNCH(C4H3N-2)}2Cr (1) and {ArNCH(C4H3N-2)}2Cr(µ-Cl)2Li(THF)2
(2), have been prepared in high yield by treatment of the sodium and lithium salts of ArNCH(C4H3NH-2)
(Ar = 2,6-i-Pr2C6H3) with CrCl2(THF) and CrCl3(THF)3, respectively. The molecular structure of 1 reveals a square planar geometry about chromium with the pyrrolide-N units disposed mutually trans. Conversely, an octahedral geometry is exhibited by the chromium centre in 2 with mutually cis-oriented pyrrolide-N units and cis-chloride ligands which, in turn, link to a Li(THF)2 unit. Complex 2 can be alkylated with AlR3 to give the five-coordinate mono-alkyl species {ArNCH(C4H3N-2)}2CrR (3a R = Me; 3b R = Et), in which two pyrrolide-imine ligands occupy the square base of the square pyramidal chromium centre. Complexes 1–3 behave as ethylene polymerisation catalysts upon treatment with an excess of a range of aluminium activators including MAO, Et2AlCl and Me2AlCl, converting ethylene to high molecular weight polyethylene. In all cases the dialkylaluminium chlorides are superior co-catalysts to MAO, affording acitivities up to 120 g mmol−1 h−1 bar−1. The coordinatively unsaturated bis(pyrrolide-imine) chromium alkyl complexes 3a and 3b are inactive for the polymerisation of ethylene in the absence of activator.
TL;DR: Ofloxacin (oflo) is able to interact with Co(II) and Zn(II)-salt to form complexes with the general formula [Moflo] 2 ]· 4H 2 O, (M = Co, Zn).
TL;DR: In this paper, a neutral 3D coordination polymeric poly(CdCl2·0.5H2O) with 2,5-bis(4-pyridyl)-1,3,4-oxodiazole (bpo) and NH4SCN in a 1:1:2 molar ratio under CH3CN−H 2O medium afforded a novel neutral three-dimensional (3D) coordination polymer.
Abstract: Reaction of CdCl2·0.5H2O with 2,5-bis(4-pyridyl)-1,3,4-oxodiazole (bpo) and NH4SCN in a 1:1:2 molar ratio under CH3CN−H2O medium afforded a novel neutral three-dimensional (3D) coordination polymer {[Cd(bpo)(SCN)2]·CH3CN}n (1) [monoclinic, space group P21/c, a = 7.680(2) A, b = 10.029(3) A, c = 25.786(7) A, β = 93.779(5)°, Z = 4]. The crystal structure reveals that 1 has a 3D noninterpenetrating open framework with guest CH3CN molecules in the cavities, in which the CdII centers (with CdN4S2 octahedral geometry) are bridged by the bpo molecules and SCN- groups. It is interesting that the two-dimensional sheet in this 3D network consists of 16-membered [Cd4(μ-SCN-N,S)4] rings, and the bpo molecules extend these layers to a 3D structure, which is further stabilized by C−H···N hydrogen-bonding and strong π−π-stacking interactions. Thermogravimetric analysis and X-ray powder diffraction technique measurements illustrate that the framework of 1 is retained upon removal of the uncoordinated guest acetonitrile m...
TL;DR: The new metal derivatives reported here were more bactericidal against one or more bacterial species as compared to the uncomplexed Schiff bases.
Abstract: Nicotinic acid derived Schiff bases and their transition metal [cobalt(II), nickel(II) and zinc(II)] complexes have been prepared and characterized by physical, spectral and analytical data. The Schiff bases act as deprotonated tridentate ligands for the complexation of the above mentioned metal ions. These complexes, possessing the general formula [M(L) 2] [where M=Co(II), Ni(II) and Zn(II) and L=HL 1 -HL 4] showed an octahedral geometry of the metal ions. For determining the effect of metal ions upon chelation, the Schiff bases and their complexes have been screened for antibacterial activity against several pathogenic strains of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The new metal derivatives reported here were more bactericidal against one or more bacterial species as compared to the uncomplexed Schiff bases.
TL;DR: Four new mononuclear complexes with significant overlap between molecular magnetic orbitals leading to rather strong intermolecular antiferromagnetic interactions are synthesized and structurally and magnetically characterized.
Abstract: Four new mononuclear complexes of formula Cd(PN)(4)(NCS)(2) (A), Cd(PNN)(4)(N(3))(2) (B), Zn(PNN)(4)(N(3))(2) (C), and Zn(PNN)(2)(NCS)(2) (D), where PNN stands for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and PN for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl, were synthesized and structurally and magnetically characterized. The X-ray structures of compounds B and C were also determined at 90 K. Compounds A[bond]C crystallize in the triclinic space group P 1 macro (No. 2), and D crystallizes in the monoclinic space group P2(1)/m (No. 11). A[bond]C adopt a centrosymmetric distorted octahedral geometry in which the metal ions are bonded to four radical ligands through the nitrogen atom of the pyridyl rings and the azido or thiocyanato ligands occupy the apical positions. Compound D adopts a distorted tetrahedral geometry in which the zinc ion is bonded to two radicals and two thiocyanato ligands. As suggested by their magnetic behavior, the low-temperature X-ray structures of B and C show that these compounds undergo a clear structural change with respect to the room-temperature structures. The experimental magnetic behaviors were perfectly reproduced by a dimer model for A[bond]C and an alternating chain model for D while the sudden breaks observed in the chi(M)T versus T curves for B and C were well accounted for by the high- and low-temperature X-ray structures. For all these complexes the crystal structures favor significant overlap between molecular magnetic orbitals leading to rather strong intermolecular antiferromagnetic interactions.
TL;DR: In this paper, the preparation, crystal structure and magnetic properties of PPh 4 [Cr(bpym)(C 2 O 4 ) 2 ]·H 2 O ( 1 ) and [Ag(BPym)] are described.
TL;DR: The copper conjugate exhibits a significant enhancement in the antitubercular activity probably arising out of its rapid intracellular reduction leading to oxygen activation, which is detrimental to the mycobacteria as discussed by the authors.
TL;DR: In this paper, a distorted mer-octahedral structure of the Schiff base has been determined by X-ray diffraction, where the ligands are coordinated as uninegatively charged tridentate chelating agents via pyridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms.
Abstract: New cadmium(II) complexes of empirical formulae, [Cd(dpksme)X] (dpksme = anionic form of the Schiff base; X = NCS−, Cl−, I−) and [Cd(dpksme)2] · 0.5MeOH, respectively have been prepared and characterized. The mono-ligated cadmium(II) complexes, [Cd(dpksme)X] are four-coordinate and tetrahedral but the bis-ligand complex, [Cd(dpksme)2] · 0.5MeOH is six-coordinate and octahedral. The crystal and molecular structure of [Cd(dpksme)2] · 0.5MeOH has been determined by X-ray diffraction. The complex has a distorted mer-octahedral structure in which the ligands are coordinated as uninegatively charged tridentate chelating agents via the pyridine nitrogen atoms, the azomethine nitrogen atoms and the thiolate sulfur atoms. The distortion from regular octahedral geometry is ascribed to the restricted bite angles of the ligands. The Schiff base and its cadmium(II) complexes exhibit mild antibacterial activities against Shigella dysenteriae, Bacillus cereus, Staphylococcus aureus and Escherichia coli. They are also mildly fungitoxic against the phytopathogenic fungi, Alternaria alternata and Macrophomina phaseolina.
TL;DR: Biological tests against four different cell lines in vitro showed that the Mn(II) complex had significant antitumor properties since the 50% inhibition concentrations of the complex were within a microM range similar to those of antitumors drug 5-fluorouracil.
TL;DR: In this paper, the reaction of Co(NO3)2 or Cd(NO 3)2 with 1,3-bis(4-pyridyl)propane (or bpp) in a mixture of benzene and methanol generates one-dimensional (1-D) coordination polymers.
TL;DR: The 1,2-bis (1H-benzimidazol-2-yl)-1,2ethanediol, 1, and its methylated derivative 2 are readily synthesized from tartaric acid, and act as chiral, facially coordinating tridentate ligands, forming complexes of composition ML2 with octahedral transition metals.
Abstract: The ligand 1,2-bis(1H-benzimidazol-2-yl)-1,2-ethanediol, 1, and its methylated derivative 2 are readily synthesized from tartaric acid, and act as chiral, facially coordinating tridentate ligands, forming complexes of composition ML2 with octahedral transition metals. The copper(II) complexes show distorted 4 + 2 coordination with benzimidazoles occupying the equatorial sites and alcohol functions weakly binding in the axial sites. Nickel(II) complexes in three different states of protonation show regular octahedral geometry with the alcohols mutually cis. Deprotonation of the coordinated alcohol produces little structural change but the monodeprotonated complex forms a hydrogen bonded dimer. Magnetic measurements show the hydrogen bonded bridge to offer a pathway for weak antiferromagnetic coupling. UV-Visible spectroscopy shows the ligand to have a field intermediate between water and pyridine. The diastereoselectivity of complexation depends on the geometry: nickel(II) shows a weak preference for the homochiral complex, whereas copper(II) forms almost exclusively homochiral complexes.
TL;DR: The results indicate that the active-site structure of TM-3, among the know structures of SVMPs examined thus far, is most similar to that of TACE owing to their close disulfide configurations and the S'(1) specificity pocket.
Abstract: The crystal structure of TM-3, a small snake-venom metalloproteinase (SVMP) isolated from Taiwan habu (Trimeresurus mucrosquamatus), was determined at 1.35 A resolution with resultant R and Rfree values of 0.181 and 0.204, respectively. The overall structure of TM-3 is an oblate ellipsoid that contains three disulfide crosslinks, Cys118–Cys197, Cys159–Cys181 and Cys161–Cys164. It exhibits the typical structural features of SVMPs and is closely related to the structure of the catalytic proteinase domain of TNFα-converting enzyme (TACE). In the present structure, the essential catalytic zinc ion was found to be replaced by a cadmium ion during crystallization, as revealed by atomic absorption analysis and X-ray data. This cadmium ion is bound to six ligands, including three conserved histidines and three water molecules, displaying the coordination geometry of a distorted octahedron. One of the water molecules is proposed to play the role of stabilizing the tetrahedral intermediate during the catalysis of SVMPs. The putative {\rm S}'_1 specificity pocket of TM-3 is relatively shallow, in contrast to the deep pockets of adamalysin II, atrolysin C and H2-proteinase, but is similar to those in acutolysin A and TACE. The shallow pocket is a consequence of the presence of the non-conserved disulfide bond Cys159–Cys181 and the residue Gln174 at the bottom of the {\rm S}'_1 pocket. The results indicate that the active-site structure of TM-3, among the know structures of SVMPs examined thus far, is most similar to that of TACE owing to their close disulfide configurations and the {\rm S}'_1 specificity pocket.
TL;DR: Three copper(II) complexes of a novel pyrazole containing porphyrinogen and cobalt(III) and zinc(II), containing tripodal ligand having N-donor atoms have been investigated and show distorted square pyramidal coordination environments for 1a and 1b with the water molecule occupying the apical site, while for complex 2 a distorted octahedral geometry is obtained.
Abstract: Copper(II) complexes of a novel pyrazole containing porphyrinogen and cobalt(III) and zinc(II) complexes of a pyrazole containing tripodal ligand having N-donor atoms have been investigated. 5-Methyl-3-formylpyrazole (MPA) on reaction with copper(II) nitrate or perchlorate in the presence of tris(2-aminoethyl)amine (tren) forms novel pyrazole-based porphyrinogen complexes [Cu(T(3)-porphyrinogen)(H(2)O)](NO(3))(2) (1a) and [Cu(T(3)-porphyrinogen)(H(2)O)](ClO(4))(2) (1b) where T(3)-porphyrinogen is 1,6,11,16-tetraaza-5,10,15,20-tetrahydroxy-2,7,12,17-tetramethylporphyrinogen. The same products are also obtained when tren is replaced by triethylamine. By contrast, the reaction between MPA, tren, and cobalt(II) perchlorate produces the cobalt(III) complex [Co(HMPz(3)tren)]ClO(4) (2) derived from the tripodal Schiff base tris[4-(3-(5-methyl-pyrazolyl)-3-aza-3-butenyl]amine (H(3)MPz(3)tren). The X-ray crystal structures of the copper(II) complexes (1a and 1b) and the cobalt(III) complex (2) have been determined. The structures show distorted square pyramidal coordination environments for 1a and 1b with the water molecule occupying the apical site, while for complex 2 a distorted octahedral geometry is obtained. Data for 1a follow: a = 19.476(3) A, b = 9.4116(8) A, c = 14.204(3) A; alpha = 90 degrees = gamma, beta = 107.58(2) degrees; V = 2482.0(7) A(3), Z = 4. Data for 1b follow: a = 20.967(3) A, b = 9.1563(18) A, c = 14.858(4) A; alpha = 90 degrees = gamma, beta = 108.44(3) degrees; V = 2706.0(10) A(3), Z = 4. Data for 2 follow: a = 21.293(3) A, b = 12.724(2) A, c = 19.777(4) A; alpha = 90 degrees = gamma, beta = 93.03(2) degrees; V = 5350.6(15) A(3), Z = 8. All three complexes crystallize in the monoclinic crystal system with the C2/c space group. The complexes are further characterized by UV-vis, IR, EPR, and electrochemical studies.
TL;DR: In this paper, Ni(H2L)Cl2]Cl2·2H2O (2), [Ni2(L)2(N3)4]·5H 2O (3) and [Ni(L)(tp)]·2 H2O(4) (L=1,3,10,12,15,18-hexaazatetracyclo[16,2,1,112.15,04.9]docosane; tp=terephthalate) have been synthesized and
TL;DR: In this article, the complexation properties of an ester derivative of clodronate with divalent metal cations Mg2+, Ca2+, Sr2+ and Ba2+ have been studied using the methods of structural chemistry and spectroscopy.
Abstract: The complexation properties of an ester derivative of clodronate with divalent metal cations Mg2+, Ca2+, Sr2+ and Ba2+ has been studied using the methods of structural chemistry and spectroscopy. A dipiperidinium salt and four alkaline earth metal complexes of the (dichloromethylene)bisphosphosphonic acid P,P′-diethyl ester: (C5H10NH2)2Cl2C(PO3Et)2 (1), [MgCl2C(PO3Et)2(H2O)3]n (2), [(H2O)3Ca{Cl2C(PO3Et)2}2Ca(H2O)3] (3), [(H2O)3Sr{Cl2C(PO3Et)2}2Sr(H2O)3]
(4) and [(H2O)2Ba{Cl2C(PO3Et)2}2Ba(H2O)2]n (5) were prepared and characterised. The crystal structures were determined with the single crystal X-ray diffraction technique. The asymmetric unit of compound 1 contains two piperidinium cations and one (dichloromethylene)bisphosphosphonic acid P,P′-diethyl ester anion, which are bound to each other by hydrogen bonding via amine-N+H2. Compound 2 is polymeric, having two independent magnesium atoms with octahedral geometry. Calcium and strontium complexes 3 and 4 are isomorphous and dimeric with seven coordinated metal atoms connected
by two Cl2C(PO3Et)22− ligands. In the asymmetric unit of complex 5, two adjacent barium atoms are joined by two Cl2C(PO3Et)22− ligands. The dimeric units are bridged through the oxygen atoms of Cl2C(PO3Et)22− and aqua ligands, forming polymeric chains. The compounds were characterised by infrared spectroscopy and 31P NMR spectroscopy. The aqueous solubility of the diethyl ester was defined in the presence of Ca2+ cations.
TL;DR: In this paper, a series of cobalt(II, III) and copper(II) complexes of 3-(2-furylidene) hydrazino-5,6-diphenyl-1,2,4-triazine (L) having formulae LMIIX2, L2MIIX 2 and LCoIIIX3, (X = Cl, OAc or ClO4; MII = CoII or CuII) were isolated and characterized by elemental analyses, molar conductances, magnetic moments and i.r
Abstract: A new series of cobalt(II, III) and copper(II) complexes of 3-(2-furylidene) hydrazino-5,6-diphenyl-1,2,4-triazine (L) having formulae LMIIX2, L2MIIX2 and LCoIIIX3, (X = Cl, OAc or ClO4; MII = CoII or CuII) were isolated and characterized by elemental analyses, molar conductances, magnetic moments and i.r., electronic and e.s.r. spectral measurements. The i.r. spectra indicated that the ligand, L, behaves as a neutral bidentate towards divalent metal ions via a triazine-N, and azomethine-N, and acts as a tridentate towards cobalt(III) via the same two nitrogen atoms and the furan-O. The magnetic moments and electronic spectral data suggest a pseudo-tetrahedral geometry for [L2Co]Cl2, a diamagnetic tetragonally distorted octahedral geometry for [LCoCl3], [LCo(OAc)3] · 4H2O and [LCo(H2O)3](ClO4)3 and a dimeric square pyramidal geometry for both [LCuCl2] and [LCu(OAc)2] · 2H2O through bridged chloro and acetato ligands, respectively. The ligand field parameters (B′, 10Dq and β) were evaluated from the electronic spectral data and magnetic moments and related to the bonding of the complexes. The X-band e.s.r. spectra showed three g values with large magnetic anisotropy for [L2Co]Cl2 in accordance with pseudo-tetrahedral CoII complexes; axial pattern for [LCuCl2], [LCu(OAc)2] · 2H2O and [L2Cu(H2O)2](ClO4)2 with two g values and a signal due to ΔMs = ±2 transition for both chloro and acetato copper(II) complexes.
TL;DR: In this article, two isomorphous polymeric complexes, [M(HL)(H2O)3]n [M = Ni, (4); Co, (5)], with one-dimensional chain structures were crystallized in the orthorhombic space group P212121, with a 7.7438(7), b 7.6997(10) A, Z 4 for (5).
Abstract: Solvothermal reactions of M(OAc)2 (M = Ni, Co) with orotic acid (2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid, H3L) in H2O/MeOH (1 : 1) gave rise to two new isomorphous polymeric complexes, [M(HL)(H2O)3]n [M = Ni, (4); Co, (5)], with one-dimensional chain structures. Both complexes crystallize in the orthorhombic space group P212121, with a 7.7438(7), b 7.7610(7), c 14.6528(12) A, Z 4 for (4), and a 7.7005(3), b 7.8725(3), c 14.6997(10) A, Z 4 for (5). X-Ray diffraction analysis shows that the metal ion is coordinated by nitrogen and oxygen atoms of an orotate ligand (HL2–) and water molecules in a distorted octahedral geometry. The hydrogen-bond interactions between chains leads to the formation of three-dimensional network structures.
TL;DR: In this article, the half-sandwich type complexes of Ni (II) and Co(II) with the less-hindered hydrotris(3,5-dimethyl-4-X-1-pyrazolyl)borate ligands were synthesized by dropwise addition of a THF solution of NaTpMe2,X to an excess amount of ML2 dissolved in MeOH.
Abstract: The selective synthesis of half-sandwich type complexes of Ni(II) and Co(II) with the less-hindered hydrotris(3,5-dimethyl-4-X-1-pyrazolyl)borate [X = Me (TpMe3; a series), H (TpMe2; b series), and Br (TpMe2,Br; c series)] ligands, [TpMe2,XMII(κ2-O,O′-L)] [L = NO3 (2), OAc (3)], has been achieved by dropwise addition of a THF solution of NaTpMe2,X to an excess amount of ML2 dissolved in MeOH. The solid state structures of the nitrato complexes 2 have been characterized by X-ray crystallography as their solvated form, 2·solv. (solv. = MeCN, MeOH), in which the metal centers have the six-coordinated octahedral geometry. Solvates are readily dissociated from the metal center upon dissolution in non-coordinationg solvents, such as CH2Cl2 and toluene, as well as drying of a solid sample to give the non-solvated five-coordinated species 2. The crystal structure of the non-solvated TpMe2Ni derivative 3bNi consists of a highly distorted trigonal bipyramidal nickel center.