Showing papers in "Inorganic Chemistry in 2000"

Programming the assembly of two- and three-dimensional architectures with DNA and nanoscale inorganic building blocks.

Abstract: The use of biochemical molecular recognition principles for the assembly of nanoscale inorganic building blocks into macroscopic functional materials constitutes a new frontier in science. This article details efforts pertaining to the use of sequence-specific DNA hybridization events and novel inorganic surface coordination chemistry to control the formation of both two- and three-dimensional functional architectures.

Evolution of the Jahn-Teller distortion of MnO6 octahedra in RMnO3 perovskites (R = Pr, Nd, Dy, Tb, Ho, Er, Y): a neutron diffraction study.

Abstract: Stoichiometric RMnO3 perovskites have been prepared in the widest range of R3+ ionic sizes, from PrMnO3 to ErMnO3. Soft-chemistry procedures have been employed; inert-atmosphere annealings were required to synthesize the materials with more basic R cations (R = Pr, Nd), in order to minimize the unwanted presence of Mn4+. On the contrary, annealings in O2 flow were necessary to stabilize the perovskite phases for the last terms of the series, HoMnO3, ErMnO3, and YMnO3, thus avoiding or minimizing the formation of competitive hexagonal phases with the same stoichiometry. The samples have been investigated at room temperature by high-resolution neutron powder diffraction to follow the evolution of the crystal structures along the series. The results are compared with reported data for LaMnO3. The distortion of the orthorhombic perovskite (space group Pbnm), characterized by the tilting angle of the MnO6 octahedra, progressively increases from Pr to Er due to simple steric factors. Additionally, all of the pe...

Platinum diimine bis(acetylide) complexes: synthesis, characterization, and luminescence properties.

Abstract: A new set of luminescent platinum(II) diimine complexes has been synthesized and characterized. The anionic ligands in these complexes are arylacetylides. The complexes are brightly emissive in fluid solution with relative emission quantum yields phiem ranging from 3 x 10(-3) to 10(-1). Two series of complexes have been investigated. The first has the formula Pt(Rphen)(C...CC6H5)2 where Rphen is 1,10-phenanthroline substituted in the 5-position with R = H, Me, Cl, Br, NO2, or C...CC6H5, while the second has the formula Pt(dbbpy)(C=CC6H4X)2 where dbbpy = 4,4'-di(tert-butyl)bipyridine and X = H, Me, F, or NO2. From NMR, IR, and electronic spectroscopies, all of the complexes are assigned a square planar coordination geometry with cis-alkynyl ligands. The crystal structure of Pt(phen)(Ce-CC6H4CH3)2 confirms this assignment. All of the complexes exhibit an absorption band at ca. 400 nm that corresponds to a Pt d-->pi*diimine charge-transfer transition. The variation of lambdamax for this band with substituent variation supports this assignment. From similar changes in the energy of the solution luminescence as a function of substituents R and X, the emissive excited state is also of MLCT origin, but with spin-forbidden character on the basis of excited-state lifetime measurements (0.01-5.6 micros). The complexes undergo electron-transfer quenching, showing good Stern-Volmer behavior using 10-methylphenothiazine and N,N,N',N'-tetramethylbenzidine as reductive quenchers. Excited-state reduction potentials are estimated on the basis of a simple thermochemical analysis. Crystal data for Pt(phen)(C...CC6H4CH3)2: monoclinic, space group C2/c, a = 19.0961(1) A, b = 10.4498(1) A, c = 11.8124(2) A, beta = 108.413(1) degrees, V = 2236.49 A3, number of reflections 1614, number of variables 150, R1 = 0.0163, wR2 (I > 2sigma) = 0.0410.

Experimental Electron Density Analysis of Mn2(CO)10: Metal−Metal and Metal−Ligand Bond Characterization

Abstract: The experimental electron density ρ(r) of Mn2(CO)10 was determined by a multipole analysis of accurate X-ray diffraction data at 120 K. The quantum theory of atoms in molecules (QTAM) was applied to ρ(r) and its Laplacian ∇2ρ(r). The QTAM analysis of ρ(r) showed the presence of a bond critical point (rc); its associated bond path connects the two Mn atoms, but no cross interaction line was found between one manganese and the equatorial carbonyls of the other. The distribution of ∇2ρ(r) indicated “closed-shell” interactions for the metallic Mn−Mn bond and the dative Mn−CO bonds. The values of the topological parameters of the density at rc, ρ(rc), ∇2ρ(rc), G(rc) (kinetic energy density), and V(rc) (potential energy density), characterize the bonds and are intermediate to those corresponding to typical ionic and covalent bonds.

Organometallic- and organic-based magnets: New chemistry and new materials for the new millennium

Abstract: Organometallic- and organic-based materials exhibiting the technologically important property of bulk magnetism have been designed, prepared, and studied. These magnets are prepared via conventional organic chemistry methodologies and unlike conventional inorganic-based magnets do not require metallurgical processing. Furthermore, these magnets are frequently soluble in conventional solvents, and examples have saturation magnetizations exceeding that of iron metal on an Fe or mole basis. Also, magnets with critical temperatures exceeding room temperature, magnets with coercive fields exceeding that of Co5Sm, and thin-film magnets have been prepared. This article highlights the collective joint research executed in our, as well as Arthur J. Epstein's, laboratories.

Molecular and electronic structures of bis(pyridine-2,6-diimine)metal complexes [ML2](PF6)n (n = 0, 1, 2, 3; M = Mn, Fe, Co, Ni, Cu, Zn).

Abstract: A series of mononuclear, octahedral first-row transition metal ion complexes mer-[MIIL02](PF6)2 containing the tridentate neutral ligand 2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine (L0) and a MnII, FeII, CoII, NiII, CuII, or ZnII ion have been synthesized and characterized by X-ray crystallography. Cyclic voltammetry and controlled potential coulometry show that each dication (except those of CuII and ZnII) can be reversibly one-electron-oxidized, yielding the respective trications [MIIIL02]3+, and in addition, they can be reversibly reduced to the corresponding monocations [ML2]+ and the neutral species [ML2]0 by two successive one-electron processes. [MnL2]PF6 and [CoL2]PF6 have been isolated and characterized by X-ray crystallography; their electronic structures are described as [MnIIIL12]PF6 and [CoIL02]PF6 where (L1)1- represents the one-electron-reduced radical form of L0. The electronic structures of the tri-, di-, and monocations and of the neutral species have been elucidated in detail by a co...

Coordination chemistry of trivalent lanthanide and actinide ions in dilute and concentrated chloride solutions.

Abstract: We have used EXAFS spectroscopy to investigate the inner sphere coordination of trivalent lanthanide (Ln) and actinide (An) ions in aqueous solutions as a function of increasing chloride concentration. At low chloride concentration, the hydration numbers and corresponding Ln,An-O bond lengths are as follows: La3+, N = 9.2, R = 2.54 A; Ce3+, N = 9.3, R = 2.52 A; Nd3+, N = 9.5, R = 2.49 A; Eu3+, N = 9.3, R = 2.43 A; Yb3+, N = 8.7, R = 2.32 A; Y3+, N = 9.7, R = 2.36 A; Am3+, N = 10.3, R = 2.48 A; Cm3+, N = 10.2, R = 2.45 A. In ca. 14 M LiCl, the early Ln3+ ions (La, Ce, Nd, and Eu) show inner sphere Cl- complexation along with a loss of H2O. The average chloride coordination numbers and Ln-Cl bond lengths are as follows: La3+, N = 2.1, R = 2.92 A; Ce3+, N = 1.8, R = 2.89 A; Nd3+, N = 1.9, R = 2.85 A; Eu3+, N = 1.1, R = 2.81 A. The extent of Cl- ion complexation decreases going across the Ln3+ series to the point where Yb3+ shows no Cl- complexation and no loss of coordinated water molecules. The actinide ions, Am3+ and Cm3+, show the same structural effects as the early Ln3+ ions, i.e., Cl- ion replacement of the H2O at high chloride thermodynamic activities. The Clion coordination numbers and An-Cl bond lengths are: Am3+, N = 1.8, R = 2.81 A; Cm3+, N = 2.4, R = 2.76 A. When combined with results reported previously for Pu3+ which showed no significant chloride complexation in 12 M LiCl, these results suggest that the extent of chloride complexation is increasing across the An3+ series. The origin of the differences in chloride complex formation between the Ln3+ and An3+ ions and the relevance to earlier work is discussed.

High-pressure synthesis of a new silicon clathrate superconductor, Ba8Si46.

Abstract: A new silicon clathrate compound with a composition of Ba8Si46 was prepared under high-pressure and high-temperature conditions. The compound was isomorphous with Na8Si46 and became a superconductor with a transition temperature of 8.0 K. Barium atoms occupy all of the Si20 and Si24 cages of the clathrate structure. This is the first clathrate superconductor obtained as a bulk phase.

Influence of anionic ligands (X) on the nature and magnetic properties of dinuclear LCuDgX3.nH2O complexes (LH2 standing for tetradentate Schiff base ligands deriving from 2-hydroxy-3-methoxybenzaldehyde and X being Cl, N3C2, and CF3COO).

Abstract: The monometallic precursor L1Cu (L1H2 standing for 1,3-bis((3-methoxysalicylidene)amino)-2,2'-dimethylpropane) reacts with GdC13 x 6H2O to afford a dinuclear complex which crystallizes in the orthorhombic space group Pca2(1) (No. 29) in a cell having the dimensions a = 9.0246(11) A, b = 16.5198(14) A, c = 20.286(2) A, and Z = 4. Analysis of the structural data shows that it may be formulated as [L1CuCl2Gd(H2O)4]Cl x 2H2O. The cationic dinuclear unit possesses a CuO2Gd bridging core which is almost planar. The complex displays a ferromagnetic interaction (10.1 cm(-1) which is the largest yet reported for a structurally characterized dinuclear (Cu-Gd) complex. Lower magnetic interactions are observed for neutral L1CuGdX3 x H2O complexes (X = N3C2, CF3COO). Consideration of the magnetic and structural data obtained for various dinuclear (Cu-Gd) complexes leads to a correlation between the magnitude of the magnetic interaction and the exponential of the dihedral angle between the two halves of the CuO2Gd bridging core.

Coordination Polymers of Copper(I) Halides

Abstract: A total of 21 complexes of CuX (X = Cl, Br, I) with bridging ligand (B = 4,4'-dipyridyl (Bpy), pyrazine (Pyz), quinoxaline (Quin), phenazine (Phz), 1,4-diazabicyclo[2.2.2]octane (DABCO), and hexamethylenetetramine (HMTA)) have been synthesized. The products show two stoichiometries: [CuXB] (type 1) and [(CuX)2B] (type 2). Both types can be obtained for B = Bpy, depending on the conditions of preparation. In these cases, the type 2 stoichiometry is the kinetic product. Type 2 complexes only are found for B = Pyz (X = I), Quin, Phz, DABCO, and HMTA. Type 1 complexes form for Pyz (X = Cl, Br). Thermogravimetic analyses of the complexes reveal the general decomposition trend: 1 --> 2 --> [(CuX)2B(1/2)] --> CuX. The X-ray crystal structure of [CuBr(Pyz)] (type 1) features copper atoms bridged by Br and Pyz, forming 2D sheets of fused rectangular Cu4Br2(Pyz)2 units. The X-ray structure of [(CuI)2(Quin)] (type 2) shows 2D layers composed of [Cu2I2]infinity "stair step" chains which are cross-linked by Quin ligands. A total of 16 complexes of CuXL (L = P(OPh)3) with bridging ligand (B = those above and 1,4-dimethylpiperazine (DMP)) have also been prepared. All of these products, except those of HMTA, are of type 3 formulation, [(CuXL)2B]. The HMTA products have the formula [CuX(HMTA)], type 4. Thermal decomposition of the type 3 and 4 complexes occurs with initial loss of B, L, or both. The X-ray structures of [(CuBrL)2(Bpy)] and [(CuBrL)2(Pyz)] (type 3) reveal 1D chains formed from rhomboidal (LCu)2Br2 units linked by the B ligand. The type 4 structure of [CuBrL(HMTA)] is shown by X-ray to be a simple halide-bridged dimer.

Nanophase cobalt oxyhydroxide mineral synthesized within the protein cage of ferritin.

Abstract: The empty protein cage of ferritin has been used to synthesize and entrap nanoscale particles of a green cobalt oxide via oxidative hydrolysis of Co(II) by H2O2. The resulting composite material retains the properties of the protein while incorporating the characteristics of the encapsulated mineral. The visible absorption spectrum has a broad band at 350 nm and the IR spectrum shows a band at 587 cm-1 characteristic of the cobalt oxyhydroxide Co(O)OH.

Mononuclear (nitrido)iron(V) and (oxo)iron(IV) complexes via photolysis of [(cyclam-acetato)FeIII(N3)]+ and ozonolysis of [(cyclam-acetato)FeIII(O3SCF3)]+ in water/acetone mixtures.

Abstract: Reaction of the monoanionic, pentacoordinate ligand lithium 1,4,8,11-tetraazacyclotetradecane-1-acetate, Li(cyclam-acetate), with FeCl3 yields, upon addition of KPF6, [(cyclam-acetato)FeCl]PF6 (1) as a red microcrystalline solid. Addition of excess NaN3 prior to addition of KPF6 yields the azide derivative [(cyclam-acetato)FeN3]PF6 (2a) as orange microcrystals. The X-ray crystal structure of the azide derivative has been determined as the tetraphenylborate salt (2b). Reaction of 1 with silver triflate yields [(cyclam-acetato)Fe(O3SCF3)]PF6 (3), which partially dissociates triflate in nondried solvents to yield a mixture of triflate and aqua bound species. Each of the iron(III) derivatives is low-spin (d5, S = 1/2) as determined by variable-temperature magnetic susceptibility measurements, Mossbauer and EPR spectroscopy. The low-spin iron(II) (d6, S = 0) complexes 1red and 2ared have been prepared by electrochemical and chemical methods and have been characterized by Mossbauer spectroscopy. Photolysis of 2a at 419 nm in frozen acetonitrile yields a nearly colorless species in approximately 80% conversion with an isomer shift delta = -0.04 mm/s and a quadrupole splitting delta EQ = -1.67 mm/s. A spin-Hamiltonian analysis of the magnetic Mossbauer spectra is consistent with an FeV ion (d3, S = 3/2). The proposed [(cyclam-acetato)FeV=N]+ results from the photooxidation of 2a via heterolytic N-N cleavage of coordinated azide. Photolysis of 2a in acetonitrile solution at -35 degrees C (300 nm) or 20 degrees C (Hg immersion lamp) results primarily in photoreduction via homolytic Fe-Nazide cleavage yielding FeII (d,6 S = 0) with an isomer shift delta = 0.56 mm/s and quadrupole splitting delta EQ = 0.54 mm/s. A minor product containing high-valent iron is suggested by Mossbauer spectroscopy and is proposed to originate from [((cyclam-acetato)Fe)2(mu-N)]2+ with a mixed-valent (FeIV(mu-N)FeIII))4+S = 1/2 core. Exposure of 3 to a stream of oxygen/ozone at low temperatures (-80 degrees C) in acetone/water results in a single oxidized product with an isomer shift delta = 0.01 mm/s and quadrupole splitting delta EQ = 1.37 mm/s. A spin-Hamiltonian analysis of the magnetic Mossbauer yields parameters similar to those of compound II of horseradish peroxidase which are consistent with an FeIV=O monomeric complex (S = 1).

Confined space synthesis. A novel route to nanosized zeolites.

Abstract: Confined space synthesis is a novel method in zeolite synthesis. It involves crystallization of the zeolite inside the pore system of an inert mesoporous matrix. In this way it is possible to prepare nanosized zeolites with a controlled size distribution by proper choice of the inert matrix. Here, confined space synthesis was adopted to prepare nanosized ZSM-5, zeolite Beta, zeolite X, and zeolite A with tailored crystal size distributions using mesoporous carbon blacks as inert matrices. All zeolites were characterized by X-ray powder diffraction, transmission electron microscopy, and nitrogen adsorption/desorption prior to and after removal of the carbon matrix. ZSM-5 with Si/Al ratios of 50, 100, and infinity (silicalite-1) were synthesized with controlled average crystal sizes in the range 20-75 nm. Nanosized zeolite Beta (7-30 nm), zeolite X (22-60 nm), and zeolite A (25-37 nm) were prepared similarly. Removal of the carbon matrix by controlled combustion allows a convenient method for isolation of the pure and highly crystalline zeolites. Therefore, confined space synthesis appears to be an attractive method for preparation of zeolites with a controlled size distribution.

pH-controlled change of the metal coordination in a dicopper(II) complex of the ligand H-BPMP: crystal structures, magnetic properties, and catecholase activity.

Abstract: The dinucleating ligand 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol (H−BPMP) has been used to synthesize the three dinuclear Cu(II) complexes [Cu2(BPMP)(OH)][ClO4]2·0.5C4H8O (1), [Cu2(BPMP)(H2O)2](ClO4)3·4H2O (2), and [Cu2(H−BPMP)][(ClO4)4]·2CH3CN (3). X-ray diffraction studies reveal that 1 is a μ-hydroxo, μ-phenoxo complex, 2 a diaqua, μ-phenoxo complex, and 3 a binuclear complex with Cu−Cu distances of 2.96, 4.32, and 6.92 A, respectively. Magnetization measurements reveal that 1 is moderately antiferromagnetically coupled while 2 and 3 are essentially uncoupled. The electronic spectra in acetonitrile or in water solutions give results in accordance with the solid-state structures. 1 is EPR-silent, in agreement with the antiferromagnetic coupling between the two copper atoms. The X-band spectrum of powdered 2 is consistent with a tetragonally elongated square pyramid geometry around the Cu(II) ions, in accordance with the solid-state structure, while the spectrum in frozen solution sugges...

Helical-chain copper(II) complexes and a cyclic tetranuclear copper(II) complex with single syn-anti carboxylate bridges and ferromagnetic exchange interactions.

Abstract: Tridentate Schiff-base carboxylate-containing ligands, derived from the condensation of 2-imidazolecarboxaldehyde with the amino acids β-alanine (H2L1) and 2-aminobenzoic acid (H2L5) and the condensation of 2-pyridinecarboxaldehyde with β-alanine (HL2), d,l-3-aminobutyric acid (HL3), and 4-aminobutyric acid (HL4), react with copper(II) perchlorate to give rise to the helical-chain complexes {[Cu(μ-HL1)(H2O)](ClO4)}n (1), {[Cu(μ-L2)(H2O)](ClO4)·2H2O}n (2), and {[Cu(μ-L3)(H2O)](ClO4)·2H2O}n (3), the tetranuclear complex {[Cu(μ-L4)(H2O)](ClO4)}4 (4), and the mononuclear complex [Cu(HL5)(H2O)](ClO4)·1/2H2O (5). The reaction of copper(II) chloride with H2L1 leads not to a syn−anti carboxylate-bridged compound but to the chloride-bridged dinuclear complex [Cu(HL1)(μ-Cl)]2 (6). The structures of these complexes have been solved by X-ray crystallography. In complexes 1−4, roughly square-pyramidal copper(II) ions are sequentially bridged by syn−anti carboxylate groups. Copper(II) ions exhibit CuN2O3 coordination e...

Synthesis and characterization of water-soluble silver(I) complexes with L-histidine (H2his) and (S)-(-)-2-pyrrolidone-5-carboxylic acid (H2pyrrld) showing a wide spectrum of effective antibacterial and antifungal activities. Crystal structures of chiral helical polymers [Ag(Hhis)]n and ([Ag(Hpyrrld)]2)n in the solid state.

Abstract: Two water-soluble, silver(I) complexes showing a wide spectrum of effective antibacterial and antifungal activities, i.e., {[Ag(Hhis)]·0.2EtOH}2 (1; H2his = l-histidine) and [Ag(Hpyrrld)]2 (3; H2pyrrld = (S)-(−)-2-pyrrolidone-5-carboxylic acid) were prepared. In aqueous solution 1 and 3 were present as dimers, whereas in the solid state they were polymers. Crystallization of 1 by slow evaporation and/or vapor diffusion gave water-insoluble crystals of [Ag(Hhis)]n (2) showing modest antimicrobial activities. The complex 1 in the solid state is a polymer formed by intermolecular hydrogen-bonding interactions between dimeric [Ag(Hhis)]2 cores, while 2 is a different polymer without a core complex. X-ray crystallography revealed that 2 was a left-handed helical polymer consisting of a bent, 2-coordinate silver(I) atom bonding to the Namino atom of one Hhis- ligand and the Nπ atom of a different Hhis- ligand. Of particular note is the fact that Ocarboxyl atoms do not participate in the coordination. X-ray crys...

Single-molecule magnets: a new class of tetranuclear manganese magnets.

Abstract: The preparation, X-ray structure, and detailed physical characterization are presented for a new type of single-molecule magnet [Mn4(O2CMe)2(pdmH)6](ClO4)2 (1). Complex 1·2MeCN·Et2O crystallizes in the triclinic space group P1, with cell dimensions at 130 K of a = 11.914(3) A, b = 15.347(4) A, c = 9.660(3) A, α = 104.58(1)°, β = 93.42(1)°, γ = 106.06(1)°, and Z = 1. The cation lies on an inversion center and consists of a planar Mn4 rhombus that is mixed-valent, MnIII2MnII2. The pdmH- ligands (pdmH2 is pyridine-2,6-dimethanol) function as either bidentate or tridentate ligands. The bridging between Mn atoms is established by either a deprotonated oxygen atom of a pdmH- ligand or an acetate ligand. The solvated complex readily loses all acetonitrile and ether solvate molecules to give complex 1, which with time becomes hydrated to give 1·2.5H2O. Direct current and alternating current magnetic susceptibility data are given for 1 and 1·2.5H2O and indicate that the desolvated complex has a S = 8 ground state...

Organic−Inorganic Perovskites Containing Trivalent Metal Halide Layers: The Templating Influence of the Organic Cation Layer

Abstract: Thin sheetlike crystals of the metal-deficient perovskites (H2AEQT)M2/3I4 [M = Bi or Sb; AEQT = 5,5‘ ‘‘-bis(aminoethyl)-2,2‘:5‘,2‘ ‘:5‘ ‘,2‘ ‘‘-quaterthiophene] were formed from slowly cooled ethylene glycol/2-butanol solutions containing the bismuth(III) or antimony(III) iodide and AEQT·2HI salts. Each structure was refined in a monoclinic (C2/m) subcell, with the lattice parameters a = 39.712(13) A, b = 5.976(2) A, c = 6.043(2) A, β = 92.238(5)°, and Z = 2 for M = Bi and a = 39.439(7) A, b = 5.952(1) A, c = 6.031(1) A, β = 92.245(3)°, and Z = 2 for M = Sb. The trivalent metal cations locally adopt a distorted octahedral coordination, with M−I bond lengths ranging from 3.046(1) to 3.218(3) A (3.114 A average) for M = Bi and 3.012(1) to 3.153(2) A (3.073 A average) for M = Sb. The new organic−inorganic hybrids are the first members of a metal-deficient perovskite family consisting of (Mn+)2/nV(n-2)/nX42- sheets, where V represents a vacancy (generally left out of the formula) and the metal cation valence,...

Ferromagnetism in Malonato-Bridged Copper(II) Complexes. Synthesis, Crystal Structures, and Magnetic Properties of {[Cu(H2O)3][Cu(mal)2(H2O)]}n and {[Cu(H2O)4]2[Cu(mal)2(H2O)]}[Cu(mal)2(H2O)2]{[Cu(H2O)4][Cu(mal)2(H2O)2]} (H2mal = malonic Acid)

Abstract: Three malonato-bridged copper(II) complexes of the formulas {[Cu(H2O)3][Cu(C3H2O4)2(H2O)]}n (1), {[Cu(H2O)4]2[Cu(C3H2O4)2(H2O)]}[Cu(C3H2O4)2(H2O)2]{[Cu(H2O)4] [Cu(C3H2O4)2(H2O)2]} (2), and [Cu(H2O)4][Cu(C3H2O4)2(H2O)2] (3) (C3H2O4 = malonate dianion) have been prepared, and the structures of the two former have been solved by X-ray diffraction methods. The structure of compound 3 was already known. Complex 1 crystallizes in the orthorhombic space group Pcab, Z = 8, with unit cell parameters of a = 10.339(1) A, b = 13.222(2) A, and c = 17.394(4) A. Complex 2 crystallizes in the monoclinic space group P2/c, Z = 4, with unit cell parameters of a = 21.100(4) A, b = 21.088(4) A, c = 14.007(2) A, and β = 115.93(2)°. Complex 1 is a chain compound with a regular alternation of aquabis(malonato)copper(II) and triaquacopper(II) units developing along the z axis. The aquabis(malonato)copper(II) unit acts as a bridging ligand through two slightly different trans-carboxylato groups exhibiting an anti−syn coordination ...

Is ferromagnetism an intrinsic property of the CuII/GdIII couple? 1. Structures and magnetic properties of two novel dinuclear complexes with a mu-phenolato-mu-oximato (Cu,Gd) core.

Abstract: Two original dinuclear (CuII,GdIII) complexes (1 and 2) deriving from polydentate nonsymmetrical Schiff base ligands LiH2 have been prepared. Formally they differ by the length of the diamino chain. They crystallize in the orthorhombic Pbca (No. 61) (1) and in the monoclinic P21/n (No. 14) (2) space groups. The cell parameters are a = 12.6295(7) A, b = 20.7894(9) A, c = 18.3301(13) A, and Z = 8 for 1 and a = 12.7246(16) A, b = 13.5691(17) A, c = 14.5310(19) A, β = 94.629(16)°, and Z = 4 for 2. These structural studies show that in both complexes the CuII and GdIII ions are doubly bridged by a phenolato oxygen atom and an oximato (N−O) pair. The bridging network is not planar. The more important distortions are observed for the complex having the larger diamino chain. Unexpectedly the latter complex presents an antiferromagnetic interaction, but the related J value is small (J ≅ −0.49 cm-1). In the former complex the interaction is ferromagnetic (J ≅ 3.5 cm-1) as it is for complexes containing (CuO2Gd) bri...

Plutonium(IV) sequestration: structural and thermodynamic evaluation of the extraordinarily stable cerium(IV) hydroxypyridinonate complexes

Abstract: Ligands containing the 1-methyl-3-hydroxy-2(1H)-pyridinone group (Me-3,2-HOPO) are powerful plutonium(IV) sequestering agents. The Ce(IV) complexes of bidentate and tetradentate HOPO ligands have been quantitatively studied as models for this sequestration. The complexes Ce(L1)4, Ce(L2)4, Ce(L3)2, and Ce(L4)2 (L1 = Me-3,2-HOPO; L2 = PR-Me-3,2-HOPO; L3 = 5LI-Me-3,2-HOPO; L4 = 5LIO-Me-3,2-HOPO) were prepared in THF solution from Ce(acac)4 and the corresponding ligand. The complex Ce(L4)2 was also prepared in aqueous solution by air oxidation of the Ce(III) complex [Ce(L4)2]-. Single-crystal X-ray diffraction analyses are reported for Ce(L1)(4)x2CHCl3 [P1 (no. 2), Z = 2, a = 9.2604(2) A, b = 12.1992(2) A, c = 15.9400(2) A, alpha = 73.732(1) degrees, beta = 85.041(1) degrees, gamma = 74.454(1) degrees], Ce(L3)2x2CH3OH [P2(1)/c (no. 14), Z = 4, a = 11.7002(2) A, b = 23.0033(4) A, c = 15.7155(2) A, beta = 96.149(1) degrees], Ce(L4)(2).2CH3OH [P1 (no. 2), Z = 2, a = 11.4347(2) A, b = 13.8008(2) A, c = 15.2844(3) A, alpha = 101.554(1) degrees, beta = 105.691(1) degrees, gamma = 106.746(1) degrees], and Ce(L4)2x4H2O [P2(1)/c (no. 14), Z = 4, a = 11.8782(1) A, b = 22.6860(3) A, c = 15.2638(1) A, beta = 96.956(1) degrees]. A new criterion, the shape measure S, has been introduced to describe and compare the geometry of such complexes. It is defined as [formula: see text], where m is the number of edges, delta i is the observed dihedral angle along the ith edge of delta (angle between normals of adjacent faces), theta i is the same angle of the corresponding ideal polytopal shape theta, and min is the minimum of all possible values. For these complexes the shape measure shows that the coordination geometry is strongly influenced by small changes in the ligand backbone or solvent. Solution thermodynamic studies determined overall formation constants (log beta) for Ce(L2)4, Ce(L3)2, and Ce(L4)2 of 40.9, 41.9, and 41.6, respectively. A thermodynamic cycle has been used to calculate these values from the corresponding formation constants of Ce(III) complexes and standard electrode potentials. From the formation constants and from the protonation constants of the ligands, extraordinarily high pM values for Ce(IV) are generated by these tetradentate ligands (37.5 for Ce(L3)2 and 37.0 for Ce(L4)2). The corresponding constants for Pu(IV) are expected to be substantially the same.

Strong differences in the in vitro cytotoxicity of three isomeric dichlorobis(2-phenylazopyridine)ruthenium(II) complexes.

Abstract: The three isomeric dichlororuthenium(II) complexes α-, β-, and γ-[Ru(azpy)2Cl2] (azpy = 2-phenylazopyridine) have been investigated for their cytotoxic properties against a series of tumor-cell lines. The complex α-[Ru(azpy)2Cl2] appears to have a very high cytotoxicity (on the order of magnitude as that of the well-known antitumor complexes cisplatin), which stands in contrast to the much lower cytotoxicity of the trans-dichloro complex γ-[Ru(azpy)2Cl2] and the cis-dichloro isomer β-[Ru(azpy)2Cl2].

Elemental solvothermal reaction to produce ternary semiconductor CuInE2 (E = S, Se) nanorods.

Abstract: A simple and convenient solvothermal process has been developed for the preparation of CuInE2 (E = S, Se) nanorods from the elements in ethylenediamine at 280 °C. Liquid In and the strong capacity of ethylenediamine were found to play important roles in the nanorod growth and electron-transfer process.

A new porous three-dimensional lanthanide coordination polymer.

Abstract: The open-framework coordination polymer [Er(C9H9O6)(H2O)2]·2.5H2O (C9H9O6 = cis,cis-1,3,5-cyclohexanetricarboxylate) has been synthesized under hydrothermal conditions. Each Er ion is coordinated to nine oxygen atoms belonging to two water molecules and five carboxylate ligands. Its 3-D polymeric structure possesses channels containing the guest water molecules that can be removed to afford a porous material [Er(C9H9O6)(H2O)2]. The metal−organic framework in [Er(C9H9O6)(H2O)2] can withstand the removal of 1 equiv of coordinated water.

Luminescent mononuclear and binuclear cyclometalated palladium(II) complexes of 6-phenyl-2,2 bipyridines: spectroscopic and structural comparisons with platinum(II) analogues.

Abstract: The mononuclear cyclometalated Pd(II) complexes [Pd(L1)X] (HL1 = 6-phenyl-2,2'-bipyridine; X = Cl, la; Br, 1b; I, 1c), [Pd(L1)PPh3]+ (1d), [Pd(L2-5)Cl] [2a-5a, HL2-5 = 4-(aryl)-6-phenyl-2,2'-bipyridine; aryl = phenyl (2), 4-chlorophenyl (3), 4-tolyl (4), 4-methoxyphenyl (5)] and the binuclear derivatives [Pd2(L1-5)2(mu-dppm)]2+ (1e-5e, dppm = bis(diphenylphosphino)methane) and [Pd2(L1)2(mu-dppCs)]2+, (1f, dppC5 = 1,5-bis(diphenylphosphino)pentane) were prepared. The crystal structures of 1d(ClO4), 1e(ClO4)2 x DMF, and 2e(ClO4)2 have been determined by X-ray crystallography. The magnitude of the Pd-Pd distances in le and 2e (3.230(1) and 3.320(2) A, respectively) suggest minimal metal-metal interaction, although pi-stacking of the aromatic ligands (interplanar separations 3.34 and 3.35 A, respectively) is evident. All complexes display low-energy UV absorptions at lambda approximately 390 nm, which are tentatively assigned to 1MLCT transitions; red shifts resulting from Pd-Pd interactions in the binuclear species are not apparent. The complexes in this work are non-emissive at 298 K, but the cationic derivatives exhibit intense luminescence at 77 K. The structured emissions of 1d and 1f in MeOH/EtOH glass (lambdamax 467-586 nm) and all cationic species in the solid state (lambdamax 493-578 nm) are assigned to intraligand excited states. Complexes le-5e display dual emissions in MeOH/EtOH glass at 77 K, and the broad structureless bands at lambdamax 626-658 nm are attributed to pi-pi excimeric IL transitions. A comparison between the photophysical properties of Pd(II) and Pt(II) congeners is presented.

Trinuclear N,N-bridged copper(II) complexes involving a Cu3OH core: [Cu3(mu 3-OH)L3A(H2O)2]A.(H2O)x (L = 3-acetylamino-1,2,4-triazolate; a = CF3SO3, NO3, ClO4; x = 0, 2) synthesis, X-ray structures, spectroscopy, and magnetic properties.

Abstract: The reaction of Haat [Haat = (3-acetylamino-1,2,4-triazole)] with aquated Cu(CF3SO3)2, Cu(NO3)2, and Cu(ClO4)2, respectively, in water results in the trinuclear complexes [Cu3(OH)(aat)3(CF3SO3)(H2O)2](CF3SO3) (1), [Cu3(OH)(aat)3(NO3)(H2O)2](NO3).(H2O)2 (2), and [Cu3(OH)(aat)3(ClO4)(H2O)2](ClO4) (3). The synthesis, X-ray structure, and magnetic and spectroscopic properties of the three title complexes are described. The cation of the three complexes is trinuclear with a Cu3OH skeleton which has the N-N diazine grouping of a triazole ring as bridge between each pair of copper atoms. The Cu3OH units have an average Cu-O distance of 1.991(6) (1), 2.000(6) (2), and 2.007(6) (3) A, an average Cu-Cu' distance of 3.355(2) (1), 3.341(1) (2), and 3.371(3) (3) A, and an average Cu-O-Cu' angle of 114.6(3) degrees (1), 112.4(2) degrees (2), and 115.4(3) degrees (3). The existence of the Cu3OH fragment is confirmed by a pseudotetrahedral oxygen environment, by detection of the OH hydrogen atom, and by stoichiometry. In the trinuclear unit the metal ions show, in the first approximation, a pseudo-square-planar pyramidal environment forming a CuN2O3 chromophore; three of the basal positions are occupied by N,N,O aat ligand atoms, the fourth one is occupied by the oxygen of the central OH group, and the apical site is occupied by an oxygen atom from a water molecule in the case of two of the copper(II) atoms and by an oxygen atom from the coordinating anion in the case of the third metal ion. The three compounds exhibit strong antiferromagnetic interaction, with similar J constants [J = -197.7 (1), J = -190.9 (2), J = -198.2 (3) cm-1], reaching complete spin coupling at ca. 75 K (1)/55 K (2)/95 K (3). At very low temperature the magnetic moment (magnetic susceptibility) falls below that expected for one unpaired electron. Magnetic parameters are discussed on the basis of the structural results and compared with those reported in the literature for related trimeric Cu(II) compounds with N-O or N-N peripheral bridges. Solid state EPR spectra of the three complexes recorded at liquid N temperature show axial signals. Crystal data: C14H20Cu3F6N12O12S2 (1) (Mw = 917.16) crystallizes in the monoclinic space group, P2(1)/c, Z = 4, with cell dimensions a = 13.080(2) A, b = 17.202(2) A, c = 13.840(2) A, beta = 92.40(1) degrees, and V = 3111.3(7) A3, Dcalcd = 1.958 Mg m-3; the final agreement values were R1 = 0.0582 and wR2 = 0.1462 for 7107 unique reflections. C12H24Cu3N14O14 (2) (Mw = 779.07) crystallizes in the triclinic space group, P1, Z = 2, with cell dimensions a = 9.647(2) A, b = 9.985(2) A, c = 15.314(2) A, alpha = 84.080(10), beta = 87.694(10), gamma = 65.030(10) degrees, and V = 1330.1(4) A3, Dcalcd = 1.945 Mg m-3; the final agreement values were R1 = 0.0397 and wR2 = 0.0950 for 7728 unique reflections. C12H20Cl2Cu3N12O14 (3) (Mw = 817.92) crystallizes in the monoclinic space group, P2(1)/a, Z = 4, with cell dimensions a = 14.238(5) A, b = 16.387(6) A, c = 11.678(4) A, gamma = 90.45(2) degrees, and V = 2724.6(18) A3, Dcalcd = 1.994 Mg m-3; the final agreement values were R1 = 0.0616 and wR2 = 0.1279 for 4038 unique reflections.

Molecular ladders with multiple interpenetration of the lateral arms into the squares of adjacent ladders observed for [M2(4,4'-bpy)3(H2O)2(phba)2] (NO3)(2).4H2O (M = Cu2+ or Co2+; 4,4'-bpy = 4,4'-bipyridine; phba = 4-hydroxybenzoate).

Abstract: Two isomorphous molecular ladders formulated as [M2(4,4‘-bpy)3(phba)2(H2O)2](NO3)2·4H2O (4,4‘-bpy = 4,4‘-bipyridine; phba = 4-hydroxybenzoate; M = Cu2+ or Co2+), shown by X-ray, feature a novel ladder motif having different inner rungs (4,4‘-bpy) and lateral arms (phba). Penetration of the lateral arms into the squares of adjacent ladders results in a novel 3-D network.

Syntheses, structures, and fluxionality of blue luminescent zinc(II) complexes: Zn(2,2',2"-tpa)Cl2, Zn(2,2',2"-tpa)2(O2CCF3)2, and Zn(2,2',3"-tpa)4(O2CCF3)2 (tpa = tripyridylamine).

Abstract: Three novel Zn(II) complexes containing either 2,2‘,2‘ ‘-tripyridylamine (2,2‘,2‘ ‘-tpa) or 2,2‘,3‘ ‘-tripyridylamine (2,2‘,3‘ ‘-tpa) have been synthesized and structurally characterized. Compound 1, Zn(2,2‘,2‘ ‘-tpa)Cl2, has a tetrahedral geometry while compounds 2, Zn(2,2‘,2‘ ‘-tpa)2(O2CCF3)2, and 3, Zn(2,2‘,3‘ ‘-tpa)4(O2CCF3)2, have an octahedral geometry. The 2,2‘,2‘ ‘-tpa ligand in 1 and 2 functions as a bidentate ligand, chelating to the zinc center, while the 2,2‘ ‘,3‘ ‘-tpa ligand in 3 functions as a terminal ligand, binding to the zinc center through the 3-pyridyl nitrogen atom. All three compounds emit a blue color in solution and in the solid state. The emission maxima for the three compounds in solution are at λ = 422, 426, and 432 nm, respectively. The blue luminescence of the complexes is due to a π* → π transition of the tpa ligand as established by an ab initio calculation on the free ligand 2,2‘,2‘ ‘-tpa and complex 1. Compounds 1 and 2 are fluxional in solution owing to an exchange proce...

Chemistry and insulin-mimetic properties of bis(acetylacetonate)oxovanadium(IV) and derivatives

Abstract: The syntheses and the solid state structural and spectroscopic solution characterizations of VO(Me-acac)2 and VO(Et-acac)2 (where Me-acac is 3-methyl-2,4-pentanedionato and Et-acac is 3-ethyl-2,4-pentanedionato) have been conducted since both VO(acac)2 and VO(Et-acac)2 have long-term in vivo insulin-mimetic effects in streptozotocin-induced diabetic Wistar rats. X-ray structural characterizations of VO(Me-acac)2 and VO(Et-acac)2 show that both contain five-coordinate vanadium similar to the parent VO(acac)2. The unit cells for VO(Et-acac)2 and VO(Me-acac)2 are both triclinic, P1, with a = 9.29970(10) A, b = 13.6117(2) A, c = 13.6642(2) A, alpha = 94.1770(10) degrees, beta = 106.4770(10) degrees, gamma = 106.6350(10) degrees for VO(Et-acac)2 and a = 7.72969(4) A, b = 8.1856(5) A, c = 11.9029(6) A, alpha = 79.927(2) degrees, beta = 73.988(2)degrees, gamma = 65.1790(10)degrees for VO(Me-acac)2. The total concentration of EPR-observable vanadium(IV) species for VO(acac)2 and derivatives in water solution at 20 degreesC was determined by double integration of the EPR spectra and apportioned between individual species on the basis of computer simulations of the spectra. Three species were observed, and the concentrations were found to be time, pH, temperature, and salt dependent. The three complexes are assigned as the trans-VO(acac)2.H2O adduct, cis-VO(acac)2.H2O adduct, and a hydrolysis product containing one vanadium atom and one R-acac- group. The reaction rate for conversion of species was slower for VO(acac)2 than for VO(malto)2, VO(Et-acac)2, and VO(Me-acac)2; however, in aqueous solution the rates for all of these species are slow compared to those of other vanadium species. The concentration of vanadium(V) species was determined by 51V NMR. The visible spectra were time dependent, consistent with the changes in species concentrations that were observed in the EPR and NMR spectra. EPR and visible spectroscopic studies of solutions prepared as for administration to diabetic rats documented both a salt effect on speciation and formation of a new halogen-containing complex. Compound efficacy with respect to long-term lowering of plasma glucose levels in diabetic rats traces the concentration of the hydrolysis product in the administration solution.

Syntheses and characterization of anti-inflammatory dinuclear and mononuclear zinc indomethacin complexes. Crystal structures of [Zn2(indomethacin)4(L)2] (L = N,N-dimethylacetamide, pyridine, 1-methyl-2-pyrrolidinone) and [Zn(indomethacin)2(L1)2] (L1 = ethanol, methanol).

Abstract: The syntheses and spectral and structural characterizations of Zn(II) indomethacin [1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid = IndoH] complexes, as different solvent adducts, ...