Xiang Ouyang

New Insight into the Nature of Cu(TCNQ): Solution Routes to Two Distinct Polymorphs and Their Relationship to Crystalline Films That Display Bistable Switching Behavior

Syntheses and characterization of two polymorphs of Cu(TCNQ) have been carried out and the results correlated to films of the materials. Reactions of CuI with TCNQ or [Cu(CH3CN)4][BF4] with TCNQ- lead to blue-purple needles of Cu(TCNQ) phase I (1). A slurry of this kinetic product in CH3CN yields a second crystalline phase of Cu(TCNQ), phase II (2), which exhibits a platelet morphology. Powder X-ray diffraction and scanning electron microscopy data revealed that both phases are present in films of Cu(TCNQ) formed by oxidation of Cu foil by TCNQ in CH3CN. X-ray photoelectron spectra of the two phases are indistinguishable from each other and are indicative of the presence of Cu(I). Single-crystal X-ray studies were undertaken on very small crystals of the two samples, the results of which reveal that subtle geometrical changes for the nitrile arrangements around the four-coordinate Cu(I) centers lead to major changes in the architectural framework of the polymers. Phase I was indexed in the tetragonal crys...

New approaches to magnetic clusters with hexacyanometallate building blocks

Abstract Polymeric cyanide complexes, whose archetype is the well-known Prussian blue mixed valence compound Fe4[Fe(CN)6]3, are key players in the field of molecule-based magnetism. One reason for the popularity of the cyanide ligand is that it effects strong and predictable magnetic exchange interactions between paramagnetic centers. In an effort to produce high-dimensional materials that behave as magnets, researchers in the area have focused on reactions of [M(CN)6]n− with labile cations that contain few or no protecting groups to limit the growth of polymeric phases. This article reports the syntheses and characterization of new ligand protected precursors of the types cis-[M(LL)2(S)2]2+ (S=solvent), cis-M(LL)2(CN)2 and cis-M(LL)2(O35CF3)2. Reactions of these convergent precursors with hexacyanometallate anions yield novel cyanide clusters, described along with key X-ray structures.

A novel one-dimensional structure involving µ4-TCNQ ligands and quadruply bonded dimolybdenum units (TCNQ = 7,7,8,8-tetracyanoquinodimethane)

Reaction of Mo2(O2CCF3)4 with TCNQ (TCNQ = 7,7,8,8-tetracyanoquinodimethane) in xylenes yields [Mo2(O2CCF3)4(TCNQ)0.5·m-xylene]2·[Mo2(O2CCF3)4·(m-xylene)] 1, an unprecedented one-dimensional µ4-TCNQ polymer, which is characterized by X-ray crystallography.

Structural characterization of Cd3(O3PC2H4CO2)2.2H2O from in-house X-ray powder data and NMR.

The title compound poly[[bis(mu-2-carboxylatoethylphosphonato)cadmium] dihydrate], Cd3(O3PC2H4CO2)2.2H2O, was prepared by a hydrothermal reaction and its crystal structure determined from in-house powder data. The structure was solved in both P2(1)/c and P2(1) space groups. The refinement converged with Rp = 0.1046, R(wp) = 0.1378 and Rf = 0.0763 in P2(1)/c. However, the solid-state NMR data could not be explained. The structure was then solved in P2(1) and the refinement converged with Rp = 0.0750, Rwp = 0.1022 and R(f) = 0.0409 and satisfied the NMR requirements.

Structural, electronic and magnetic properties of metal–metal bonded dinuclear rhenium complexes bridged by organocyanide acceptor ligands

The syntheses, spectroscopic properties, redox chemistry, and solid-state structures of products obtained from the reaction of Re2Cl4(dppm)2 (dppm = bis(diphenylphosphino) methane) with the polycyano acceptors TCNQ (7,7,8,8-tetracyanoquinodimethanido) and DM-DCNQI (2,5-dimethyl-N,N′-dicyanoquinonediimine) are described. The compounds [Re2Cl4(dppm)2]2(μ-TCNQ), 1, and [Re2Cl4(dppm)2]2(μ-DM-DCNQI), 2, have been prepared by reaction of two equivalents of Re2Cl4(dppm)2 with TCNQ and DMDCNQI, respectively, in THF or CH2Cl2. A single-crystal X-ray crystallographic study of [Re2Cl4(dppm)2]2(μ-TCNQ)·10THF revealed the presence of a trans-μ2 bidentate mode for the bridging TCNQ ligand that joins two Re2Cl4(dppm)2 molecules through equatorial positions. In a similar fashion, the compound [Re2Cl4(dppm)2]2(μ-DM-DCNQI)·10THF consists of two Re2 units coordinated to the two nitrile positions of the DM-DCNQI ligand. The electronic properties of both compounds are unusual in that they exhibit intense, broad absorptions that span the near-IR region and extend into the mid-IR. The electrochemistry of the compounds consists of numerous oxidation and reduction processes in the range of +2.0 to −2.0 V as determined by cyclic voltammetry. Both 1 and 2 exhibit temperature independent paramagnetism (TIP) with large χTIP values of 7.29 × 10−3 and 6.23 × 10−3 emu mol−1, respectively.

New micro- and mesoporous materials based on VOPO4 chemistry

Abstract A brief review of porosity in zeolites, pillared layers and the new mesoporous materials serves as an introduction to the present study. A dark green-layered vanadyl phosphate of composition [(VO) 3 (PO 4 ) 3 (H 2 O) 3 ]·4H 2 O was prepared hydrothermally. It was found to intercalate close to 3 mols of amine per VOPO 4 unit. These amine-intercalated phases react with inorganic polymers in alcohol as the solvent under reflux to yield both micro- and mesoporous materials. These reactions exhibit features of both pillaring and template guided reactions. Materials with very narrow pore distributions are obtained by an, as yet, undetermined mechanism. Thermal treatment leads to larger pores with a still narrow pore size distribution. The goal is to prepare catalytically active porous materials with pore diameters in the 10–20 A range.

Inorganic–organic hybrid metal complexes: 24-membered hexaazamacrocyclic dinuclear nickel complexes hybridized with CdBr 4 2−

Abstract The 24-membered macrocyclic mononuclear cadmium complex reacts with Ni(ClO4)2 in solution and unexpected dinuclear nickel complex was obtained with [CdBr4]2− as counter ions. In the homodinuclear nickel complex, two different coordination environmental entities were observed. One of these is a five-coordinated dinuclear species, the other is a six-coordinated dinuclear species [Ni(1A)2C26H40N6O2(H2O)2]. In [Ni(1A)2C26H40N6O2(H2O)2], nickel ion is coordinated to three nitrogen atoms, one phenolic oxygen from the macrocyclic ligand, and with one exogenous water molecule to complete an octahedron. In [Ni(1B)2C26H40N6O2], each nickel ion is five-coordinated without solvent interaction. [CdBr4]2− anions are located in the lattice and serve as hybrid bridges to connect two different molecules and form two layer arrays along the c axis. The whole molecule is described as an ion pair with a two-dimensional hydrogen bonding network. The average bond lengths of Ni–N and Ni–O(phenolic oxygen) are 2.083, 2.028 A.

Novel dioxotetrazamacrocyclic “sandwich” complexes – synthesis and structural characterization

Abstract Reaction of 1,4,7,10-tetraazacyclododecane-2,9-dione with copper and cobalt perchlorate in water at 1:1 molar ratio afforded two new crystal-engineered 1:2 ‘sandwich’ type complexes. Both of them are isostructural analogues. Copper complex crystallized in monoclinic space group P21/c with a=9.6888(12), b=12.2956(16), c=10.5661(13), β=104.965(2)°, V=1216.0(3) A 3 , and Z=2. The Cu(II) ions are six-coordinated by four nitrogen atoms and two amide oxygen atoms. Their coordination geometry can be described as Jahn–Teller distorted octahedra, with elongated Cu–O distances. (2.310(2) A) Cobalt complex crystallized in monoclinic space group P21/c with a=9.7560(12), b=12.237(16), c=10.7130(13), β=105.194(3)°, V=1234.2(4) A 3 , and Z=2. The Co(II) ions are also six-coordinated by similar atoms as found in copper complex. But the bond lengths of Co–O 2.0881(13) A are slightly shorter than respective Co–N.