DO Miller

Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada

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Publications (10)29.17 Total impact

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    ABSTRACT: The potentially bis-bidentate ligand 1,4-di-2′-pyridylaminophthalazine (pap), forms mononuclear (Ni(II)), dinuclear (Ni(II), Co(III)) and trinuclear (Ni(II)) complexes, with combined N–N diazine and OH (Ni(II), Co(III)), and H2O (Ni(II)) bridges. The dinuclear and trinuclear Ni(II) complexes exhibit intramolecular antiferromagnetic exchange interactions, from a combination of the exchange effects of both the N–N and `O' bridge groups.
    01/2004;
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    ABSTRACT: The tritopic hydrazide ligand m2poap (from the reaction of 4-methoxy-2,6-dicarboxylic hydrazide and methyl imino-2-picolinate) reacted with Cu(NO3)2 to produce a linear trinuclear diazine (N–N) bridged m2poap complex, and a nona-nuclear Cu(II)9 mixed ligand [3×3] grid complex, containing two 4-chloro-2,6-pyridine dicarboxylate (Clpic2−) ligands, and four deprotonated m2poap ligands. The presence of Clpic2− arises from an impurity in the ligand, which results from hydrolysis of a starting material. Clpic2− connects three Cu(II) centers in an unusual oxygen bridged coordination mode. The smaller bite of this ligand leads to a contraction of the grid, compared with homoleptic [3×3] grid examples, and results in enhanced ferromagnetic exchange within the grid. The trinuclear complex of m2poap exhibits fairly strong antiferromagentic exchange, typical of N–N bridged systems.
    Polyhedron 01/2002; 21(17):1715-1720. · 2.05 Impact Factor
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    ABSTRACT: A series of trigonal bipyramidal pentanuclear complexes involving the alkoxo-diazine ligands poap and p3oap, containing the M(5)[mu-O](6) core is described, which form by a strict self-assembly process. [Co(5)(poap-H)(6)](ClO(4))(4).3H(2)O (1), [Mn(5)(poap-H)(6)](ClO(4))(4).3.5CH(3)OH.H(2)O (2), [Mn(5)(p3oap-H)(6)](ClO(4))(4).CH(3)CH(2)OH.3H(2)O (3), and [Zn(5)(poap-H)(6)](ClO(4))(4).2.5H(2)O (4) are homoleptic pentanuclear complexes, where there is an exact match between the coordination requirements of the five metal ions in the cluster, and the available coordination pockets in the polytopic ligand. [Zn(4)(poap)(poap-H)(3)(H(2)O)(4)] (NO(3))(5).1.5H(2)O (5) is a square [2 x 2] grid with a Zn(4)[mu-O](4) core, and appears to result from the presence of NO(3), which is thought to be a competing ligand in the self-assembly. X-ray structures are reported for 1, 4, and 5. 1 crystallized in the monoclinic system, space group P2(1)/n with a = 13.385(1) A, b = 25.797(2) A, c = 28.513(3) A, beta = 98.704(2) degrees, and Z = 4. 4 crystallized in the triclinic system, space group P1 with a = 13.0897(9) A, b = 18.889(1) A, c = 20.506(2) A, alpha = 87.116(1) degrees, beta = 74.280(2) degrees, gamma = 75.809(2) degrees, and Z = 2. 5 crystallized in the monoclinic system, space group P2(1)/n with a = 14.8222(7) A, b = 21.408(1) A, c = 21.6197(9) A, beta = 90.698(1) degrees, and Z = 4. Compounds 1-3 exhibit intramolecular antiferromagnetic coupling.
    Inorganic Chemistry 09/2001; 40(17):4448-54. · 4.59 Impact Factor
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    ABSTRACT: The single-crystal structures and magnetic properties of a series of self-assembled cluster complexes of Mn(II), Co(II), Co(II)/Co(III), and Cu(II), with a group of alkoxy-diazine ligands, which have square and rectangular primary architectures, are reported. In one novel case a secondary coordination sphere of metal ions can be built up on a square core, due to the presence of vacant extra-core coordination sites. [Mn4(poapz-H)4(H2O)4](NO3)4·H2O (1); monoclinic, C2/c, a=21.7120(4) Å, b=17.421(4) Å, c=17.273(4) Å, β=109.34(3)°. [Co4(poap-H)2(poap-2H)2](NO3)4·7H2O (3); triclinic, P, a=9.6855(6) Å, b=12.9462(7) Å, c=13.7383(8) Å, α=106.5730(10), β=99.0400(10) Å, γ=95.737(10)°. [Co4(poapz-H)4(H2O)4](NO3)4·2H2O (4); monoclinic, C2/c, a=21.160(2) Å, 17.808(2) Å, c=17.000(2) Å, β=106.904(9)°. [Co4(pzoapz-H)4(H2O)4](ClO4)4·3H2O (5); monoclinic, P21/a, a=23.24(1) Å, b=13.681(3) Å, c=23.37(2) Å, β=118.17(4)°. [Cu4(poap-H)4](ClO4)4·CH3CN·4.75H2O (6); triclinic, P, a=13.966(1) Å, b=14.195(1) Å, c=19.452(2) Å, α=83.435(2)°, β=80.727(1)°, γ=63.023(1)°. [Cu5(3poap-H)3(3poap-3H)] (ClO4)4·7.5H2O (7); triclinic, P, a=11.8316(12) Å, b=14.7017(16) Å, c=21.1527(23) Å, α=92.401(2)°, β=104.690(2)°, γ=104.586(2)°. Magnetic properties are interpreted in relation to the structures. The Mn(II) complexes (1, 2) and the Co(II) complexes (4, 5) exhibit intramolecular antiferromagnetic coupling associated with large M–O–M angles, the Cu(II)4 complex 6 exhibits intramolecular ferromagnetic coupling due to magnetic orbital orthogonality, while the Cu(II)5 complex 7 is best described as a combination of a ferromagnetic trinuclear subunit and an antiferromagnetic dinuclear subunit.
    Journal of Solid State Chemistry 07/2001; · 2.04 Impact Factor
  • Inorganic Chemistry 06/2001; 40(10):2446-9. · 4.59 Impact Factor
  • Angewandte Chemie International Edition 10/2000; 39(17):3114-3117. · 11.34 Impact Factor
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    ABSTRACT: A new strategy for the synthesis of Buckybowls is presented and initial attempts to implement it are reported. This involves annulation of further rings onto polycyclic aromatic systems that prefer to be planar but have been "pre-bent" by the installation of a tether. Pyrenophane 2b reacts with TCNE and PTAD to give 1:1 and 1:2 adducts, respectively. The less strained pyrenophane 2c is unreactive toward TCNE but gives a 1:2 adduct with PTAD. Attempted electrophilic aromatic brominations of pyrenophane 2e under a variety of conditions were unsuccessful, as were attempts to brominate cyclophanediene 1c, the direct synthetic precursor of 2c. Tether cleavage and addition reactions occurred rather than substitution. In an effort to circumvent tether cleavage problems, [7]-, [8]- and [9](2,7)pyrenophanes 22b-d were prepared. However, attempted bromination and Friedel-Crafts acylations failed. Evidence for the fleeting existence of [6](2,7)pyrenophane 22a was also obtained. Comparison of structural data (X-ray and AM1 calculations) for the pyrenophanes 22a-d with their 1,n-dioxa analogues 2a-d indicates that the nature of the tether has a strong effect on the degree of bend in the pyrene moiety and this led to the identification of trioxapyrenophane 28 as the next target in the quest for increasingly bent pyrenes.
    The Journal of Organic Chemistry 09/2000; 65(17):5360-70. · 4.56 Impact Factor
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    ABSTRACT: One- and two-dimensional copper(II) complexes of the polydentate diazine ligands pahap and pypz are reported, in which two copper(II) centers are bridged by a rotationally flexible single N–N bridge in a basic dinuclear subunit, with these subunits linked by halogen atom bridges to provide extended chains and layers. Crystal structures are reported for [Cu2(pypz)Cl4]·H2O (1), [Cu2(pypz)Br4]·H2O (2) and [Cu2(pahap)Cl4] (3). In 1 and 2 the dinuclear subunits are internally bridged by halogen atoms to form tetranuclear dimers, which then link to form a two-dimensional chicken wire lattice. The dinuclear subunits exhibit intra-molecular ferromagnetic coupling, associated with acute angles of rotation of the copper magnetic planes around the N–N single bond bridge, in complete agreement with previous magneto-structural results. However, low temperature phase transitions (<15 K) indicate the presence of significant antiferromagnetic components, which are associated with spin pairing between adjacent ferromagnetic layers. In addition long range, weak ferromagnetic ordering is observed below 5 K, and confirmed by magnetic hysteresis measurements. The complicated magnetic data have been interpreted in terms of a model involving one-dimensional ferromagnetic chains arranged in two-dimensional layers, with the layers linked antiferromagnetically, leading to metamagnetic behaviour, with additional interchain ferromagnetic coupling appearing at low temperatures. Compound 3 has a much larger rotational angle of the copper magnetic planes around the N–N bond (120.3°), and a different extended structure involving a linear chain of chlorine atom bridged tetranuclear subunits. The magnetic properties of 3 are interpreted using an alternating chain model, and are dominated by intramolecular antiferromagnetic exchange between copper(II) centers within each dinuclear subunit.
    JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS. 01/2000;
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    ABSTRACT: Dinuclear and tetranuclear copper(II) complexes of three polydentate diazine ligands (pahap, pmhap, bdpah), based on potentially bridging N–N single bond fragments, are reported. The 2∶2 complexes [Cu2(pahap)2(NO3)(H2O)2][NO3]3·H2O (1) and [Cu2(pmhap)2(NO3)2][NO3]2·3H2O (2) involve dinuclear centres bridged by two N–N single bonds, and are essentially uncoupled, as a result of strict orbital orthogonality or an acute twisting of the copper magnetic planes relative to the N–N bridge. A mixed, double bridged (pyridazine/N–N) complex [Cu2(pahap)(dppn)(NO3)(H2O)][NO3]3 (3) has a larger angle between the magnetic planes, resulting in weak antiferromagnetic behaviour (2J = −32.5 cm−1). The rotationally more flexible 1∶1 complexes [Cu2(pahap)(C2O4)2]·0.5H2O (4) (2J = −4.4 cm−1) and [Cu2(pahap)(acac)2(H2O)2][NO3]2·H2O (5) (2J = −69.7 cm−1) involve single N–N bridges, and the angle between the copper magnetic planes depends on steric factors and hydrogen bonding interactions respectively. A tetranuclear complex [Cu2(pahap − H)(dpa)]2[NO3]4·4H2O (6) results from the linking of two {Cu2(N–N)} subunits with a secondary ligand strap, 1,3-diamino-2-propanol, and leads to a trans Cu2(N–N) bridging arrangement and strong antiferromagnetic coupling (2J = −186.4 cm−1). The complex [Cu2(bdpah − H)(NO3)2][NO3] (7) has a locked conformation with a large Cu–N–N–Cu torsional angle (130.3°), leading to moderately strong antiferromagnetic coupling (2J = −112.0 cm−1). The magnetic results are entirely consistent with previous magnetostructural correlations relating the twist of the copper magnetic planes around the N–N bond to the exchange integral.
    JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS. 01/2000;