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Andrew D Bond

Publications and source records attributed to Andrew D Bond.

At least 19 recordsLinked to original sources
PubMed2006

Cis- and trans-bis(2-cyanoethylsulfanyl)(decane-1,10-diyldithio)tetrathiafulvalene.

The isomeric title compounds, 2,7-bis(2-cyanoethylsulfanyl)-3,6-(decane-1,10-diyldithio)tetrathiafulvalene and 2,6-bis(2-cyanoethylsulfanyl)-3,7-(decane-1,10-diyldithio)tetrathiafulvalene, both C22H28N2S8, comprise bis(2-cyanoethylsulfanyl)tetrathiafulvalene units tethered by a saturated decamethylenedithio linker attached in either a cis or a trans manner. The tetrathiafulvalene (TTF) group is planar in the cis isomer, but distorted significantly from planarity and twisted about its long axis in the trans isomer. In both structures, intermolecular interactions are segregated into regions in which TTF units are brought into close contact and regions where the polymethylene chains are brought into close contact. In the cis isomer, TTF units exhibit pi-pi stacking interactions, while in the trans isomer they do not.

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PubMed2006

Hexaferrocenylbenzene.

Hexaferrocenylbenzene has been synthesized by six-fold Negishi type ferrocenylation of hexabromo- or hexaiodobenzene.

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PubMed2005

One-dimensional zinc-based coordination polymers incorporating cyanate anions.

Two one-dimensional zinc-based coordination polymers containing cyanate anions are reported. catena-Poly[sodium [[tricyanatozinc(II)]-mu-1,4-diazabicyclo[2.2.2]octane-kappa2N:N']], [Na[Zn(NCO)3(C6H12N2)]]n, consists of linear [tricyanatozinc(II)]-mu-1,4-diazabicyclo[2.2.2]octane strands in which the Zn2+ cations adopt trigonal-bipyramidal coordination on sites of -6m2 point symmetry. Na+ cations lie between the strands on sites of -3m point symmetry, coordinated in a distorted octahedral geometry by six O atoms of the cyanate anions. catena-Poly[[dicyanatozinc(II)]-mu-4,4'-bipyridine-kappa2N:N'], [Zn(NCO)2(C10H8N2)]n, crystallizes in the space group P2(1)/n with Z' = 5. The structure consists of zigzag strands formed by Zn2+ cations linked via 4,4'-bipyridine. Each Zn2+ cation adopts a tetrahedral coordination, with two sites occupied by 4,4'-bipyridine and two cyanate anions completing the coordination sphere. The structure is closely comparable with the thiocyanate and halide analogues [ZnX2(C10H8N2)] (X = NCS, Cl or Br).

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PubMed2005

Controlled formation and topologies of thiophenolate-based macrocycles: rings, cylinders and bowls.

The Schiff-base condensations of 1,3-diaminopropane with a protected thiophenol dialdehyde in the presence of Ni(2+), Pd(2+) or Zn(2+) can be controlled to yield either mononuclear acyclic, or 2 + 2 and 4 + 4 macrocyclic complexes by the choice of both metal cation and counteranion. The Ni(2+) complex of the 2 + 2 macrocycle contains two square-planar nickel ions and shows an arrangement similar to one observed previously: the mu-S atoms of the thiophenolate groups are pyramidal and lie on the same side of the plane defined by the four N atoms of the macrocycle to give a V-shaped molecule. By contrast, the Zn(2+) complex of the 2 + 2 macrocycle undergoes oligomerization to yield a bowl-shaped hexanuclear complex that includes a mu(3)-carbonate anion. Essential for this topology is the presence of three mu(3)-S-thiophenolato groups that link the three macrocyclic units to form a Zn(3)S(3) ring that seals the bottom part of the bowl. In this arrangement, one of the pyramidal mu(3)-S atoms in each dinuclear Zn(2+) complex is inverted relative to the arrangement observed for the dinickel complexes. Molecular modelling suggests that inversion about the mu-S atoms of the 2 + 2 macrocyclic complexes is readily accessible at room temperature and that the contrasting arrangements observed for the Ni(2+) and Zn(2+) complexes are those energetically most favourable for the respective metal ions. Rare 4 + 4 macrocyclic complexes are isolated as neutral dinuclear complexes for Ni(2+) and Pd(2+) and as a tetranuclear complex cation for Zn(2+). The topologies of these systems contrast significantly: those with two square-planar Ni(2+) or Pd(2+) ions form extended rings, while that with Zn(2+) forms a sulfur-lined cylinder which hosts acetonitrile molecules in the crystalline state. Reaction conditions can also be optimised to produce 2 + 1 acyclic ligands as their mononuclear Ni(2+) and Pd(2+) complexes, providing potentially useful building blocks for production of more complicated macrocyclic and supramolecular systems.

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PubMed2005

Squeezing the [Cu-OH...H2O-Cu]3+ bridge by cryptate encapsulation.

Treatment of cryptand L(1) with Cu(II) generates a H3O2(-)-bridged dicopper(II) cryptate, 2, where the guest anion has responded to steric constraint by a significant shortening of the O-O distance to 2.325(9) A; computational optimization at the B3LYP/6-31(d) level suggests that the bridging O-H...O H-bond is bent (approximately 157 degrees) but that the barrier to interchange of the bridging H atom is low (<4 kJ mol(-1)). This cryptate, rather than the [Cu2L(1)muCN]3+ species recently claimed to derive from cleavage of the C-C bond of the solvent, is the product of acetonitrile recrystallization of the initially formed reaction product, 1.

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PubMed2005

Second-sphere coordination in anion binding: sodium hexaamminecobalt(III) tetrakis(4-fluorobenzoate) monohydrate.

In sodium hexaamminecobalt(III) tetrakis(4-fluorobenzoate) monohydrate, Na[Co(NH3)6](C7H4FO2)4.H2O, determined at 180 K, [Co(NH3)6]3+ cations lie on centres of inversion and form layers in which their C4 axes lie perpendicular to the layer planes. 4-Fluorobenzoate anions lie on twofold axes and general positions and adopt near-planar geometries. Na+ cations and water molecules lie on twofold axes, forming [NaO5] square pyramids that lie between the [Co(NH3)6]3+ cations. The second-sphere interactions between [Co(NH3)6]3+ cations and 4-fluorobenzoate anions comprise edge-to-face and vertex-to-face arrangements. The structure is closely comparable with that of the benzoic acid salt, demonstrating that fluorination of the anion in the para position has no significant influence on the second-sphere interactions and minimal influence on the gross crystal structure.

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PubMed2005

Cascade complexation: a single cyano bridge links a pair of Cu(II) cations.

A series of structurally characterised mu-cyanodicopper(II) cryptates shows moderately strong antiferromagnetic interaction in the range -2J= 150-200 cm(-1), at the high end of the observed range for such assemblies. The lowest magnetic exchange coupling parameter is displayed where there is slight bending of the M-CN-M assembly, enforced by the constraints of cryptate encapsulation. Thermally accessible triplet EPR spectra are observed with zero-field splittings of the order of 0.13-0.14 cm(-1), confirming collinear ground-state dz2 orbitals for Cu(II), consistent with their trigonal-bipyramidal coordination geometries.

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PubMed2005

Self-assembly of the octanuclear cluster [Cu8(OH)10(NH2(CH2)2CH3)12]6+ and the one-dimensional N-propylcarbamate-linked coordination polymer {[Cu(O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n.

The reaction of Cu(ClO4)2.6-H2O and n-propylamine in methanol gives two high-nuclearity products of well-defined compositions. At amine concentrations greater than seven equivalents compared to copper ion concentration, the system fixes carbon dioxide from air to form the one-dimensional carbamate-bridged coordination polymer, {[Cu(mu2-O,O'-O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n ({1-ClO4}n). Lower relative amine concentrations lead to the self-assembly of an octanuclear copper-amine-hydroxide cluster [Cu8(OH)10(NH2(CH2)2CH3)12]6+ (2). Both compounds exhibit unique structures: {1-ClO4}n is the first mu2-O,O'-mono-N-alkylcarbamate-linked coordination polymer and 2 is the largest copper-hydroxide-monodentate amine cluster identified to date. The crystal structures indicate that the size of the n-propyl group is probably crucial for directing the formation of these compounds. Magnetic susceptibility studies indicate very weak antiferromagnetic coupling for 1. The octanuclear cluster 2 displays slightly stronger net antiferromagnetic coupling, despite the presence of a number of Cu-O(H)-Cu angles below the value of about 97 degrees that would normally be expected to yield ferromagnetic coupling.

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PubMed2005

Two new cobalt-zinc orthophosphate monohydrates: hydrothermal synthesis, crystal structures and thermal investigation.

Two new cobalt zinc orthophosphate hydrates with similar chemical formula, (CoxZn(1-x))3(PO4)2.H2O, but different composition and structure, have been prepared by systematic hydrothermal synthesis from the system nCo(CH3COO)2 : (1 -n)Zn(CH(3)COO)2 : 3.5H3PO4 : 2.1(CH3)2NH(CH2)3NH2:144H2O (0 </= n </= 1). The material Co(2.59)Zn(0.41)(PO4)2.H2O 1 has a three-dimensional structure that can be considered to be built from layers of edge-sharing CoO(6) octahedra joined by edge-sharing (Co/Zn)O(5) trigonal bipyramids, which also share edges with PO(4) tetrahedra. Compound 2, Co(0.72)Zn(2.28)(PO(4))(2).H(2)O, is isostructural with a known phase of Zn(3)(PO(4))(2).H(2)O: its structure contains corner-sharing (Zn/Co)O6 octahedra, (Zn/Co)O4 tetrahedra and PO4 tetrahedra, forming channels into which the coordinated water molecules project. Magnetic susceptibility measurements for 1 and 2 are consistent with the chemical compositions determined by the single-crystal X-ray analyses and with the presence of Co2+. The range for possible Co/Zn substitution in 1 and 2(assessed by EDX analysis) is relatively small: x lies in the range 0.74-0.80 (+/- 0.05) for 1 and 0.23-0.28 (+/- 0.05) for 2. Thermal investigation of 1 and 2 by thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC) shows that both materials transform to gamma-(CoxZn(1-x))3(PO4)2 when heated to 518 and 435 degrees C, respectively, with enthalpy changes for complete dehydration of DeltaH= 41.9 and 53.5 kJ mol(-1), respectively. Dehydration of 1 occurs in a single irreversible step, while that of 2 occurs over a greater temperature range and proceeds via several steps. A new phase, (CoxZn(1-x))3(PO4)2.0.27H2O, is formed when 2 is heated to 357 degrees C.

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PubMed2004

Aggregation control by homologous tripodal tetradentate amino acid ligands in oxo-bridged diiron(III) aquo complexes.

Isoelectronic oxo-bridged diiron(III) aquo complexes of the homologous tripodal tetradentate amino acid ligands, N,N'-bis(2-pyridylmethyl)-3-aminoacetate (bpg(-)) and N,N'-bis(2-pyridylmethyl)-3-aminopropionate (bpp(-)), containing [(H(2)O)Fe(III)-(mu-O)-Fe(III)(H(2)O)](4+) cores, oligomerise, respectively, by dehydration and deprotonation, or by dehydration only, in reversible reactions. In the solid state, [Fe(2)(O)(bpp)(2)(H(2)O)(2)](ClO(4))(2) (1(ClO(4))(2)) exhibits stereochemistry identical to that of [Fe(2)(O)(bpg)(2)(H(2)O)(2)](ClO(4))(2) (2(ClO(4))(2)), with the ligand carboxylate donor oxygen atoms and the water molecules located cis to the oxo bridge and the tertiary amine group trans to it. Despite their structural similarity, 1(2+) and 2(2+) display markedly different aggregation behaviour in solution. In the absence of significant water, 1(2+) dehydrates and dimerises to give the tetranuclear complex, [Fe(4)(O)(2)(bpp)(4)](ClO(4))(4) (3(ClO(4))(4)), in which the carboxylate groups of the four bpp(-) ligands act as bridging groups between two [Fe(2)(O)(bpp)(2)](2+) units. Under similar conditions, 2(2+) dehydrates and deprotonates to form dinuclear and trinuclear oligomers, [Fe(2)(O)(OH)(bpg)(2)](ClO(4)) (4ClO(4)) and [Fe(3)(O)(2)(OH)(bpg)(3)](ClO(4)) (5(ClO(4))), related by addition of 'Fe(O)(bpg)' units. The trinuclear 5(ClO(4)), characterised crystallographically as two solvates 5(ClO(4)).3H(2)O and 5(ClO(4)).2MeOH, is based on a hexagonal [Fe(3)(O)(2)(OH)(bpg)(3)](+) unit, formally containing one hydroxo and two oxo bridges. The different aggregation behaviour of 1(ClO(4))(2) and 2(ClO(4))(2) results from the difference of one methylene group in the pendant carboxylate arms of the amino acid ligands.

Amino Acids↗
PubMed2004

Syntheses of syn and anti doublebent [5]phenylene.

[structure: see text] The parent and dipropyl-substituted anti (1a,b) and syn doublebent (2a,b) [5]phenylenes have been assembled by CpCo-catalyzed double cyclization of regiospecifically constructed appropriate hexaynes. (1)H NMR, NICS, and an X-ray structural analysis of 1a reflect the aromatizing effect of double angular fusion on the central ring of the linear [3]phenylene substructure.

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