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Chang Seop Hong

Publications and source records attributed to Chang Seop Hong.

14 recordsLinked to original sources
PubMed2006

Cyanide-bridged single-molecule magnet constructed by an octacoordinated [W(CN)6(bpy)]- anion.

Two cyanide-bridged WV-M [M = Mn(II) (1), Co(II) (2)] bimetallic clusters were prepared by self-assembling a new molecular precursor [W(CN)6(bpy)]- and the corresponding metal complexes. Compound 1 shows a tetranuclear W2Mn2 entity, consisting of a Jahn-Teller ion, Mn(III), which serves as an anisotropic source, while compound 2 exhibits a trimeric W2Co structure. Among them, compound 1 displays slow relaxation of the magnetization, which is typical of a single-molecule magnet behavior.

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PubMed2006

Coexistence of spin canting and metamagnetism in a one-dimensional Mn(III) complex bridged by a single end-to-end azide.

Two manganese(III) azide complexes capped with tetradentate Schiff bases were characterized structurally and magnetically. The replacement of halogens on the Schiff bases leads to a drastic structural alteration from a dimer (1) bridged by phenoxide to a one-dimensional chain (2) linked by azide in a single end-to-end mode. Notably, magnetic studies of 2 show the concomitant existence of spin canting and metamagnetism.

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PubMed2006

Synthesis, crystal structures, and magnetic properties of cyano-bridged honeycomblike layers M(V)-Cu(II) (M = Mo, W) chelated by a macrocyclic ligand.

Two cyano-bridged Cu(II)-M(V) [M = Mo (2), W (3)] complexes formed by self-assembly of octacyanometalates [M(CN)8]3- (M = Mo, W) with a new molecular precursor [Cu(L2)]2+ (1) (L2 = a macrocyclic ligand) in a 2:3 ratio have been investigated in terms of structures and magnetic behaviors. The M2Cu3 repeating unit of both bimetallic compounds is extended to a two-dimensional honeycomblike layered structure. The pendant ethyl groups on L2 noticeably influence the structural parameters around the Cu center. Compared with the system composed of a macrocycle without a side group, Cu-N(ax) (ax = axial) distances become shorter and the Cu-N(ax)-C(ax) angles are more bent for 2 and 3. The magnetic data denote that the Cu(II) and M(V) spins undergo explicit ferromagnetic interactions via CN bridges. From a structural and magnetic point of view, given that the Cu-N(ax) bond length in the tetragonally distorted octahedral Cu(II) environment is long enough, the overall ferromagnetic character remains despite the variation of Cu-N(ax)-C(ax) angle in this system.

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PubMed2006

Methylpyrazole-capped two-dimensional supramolecular M(II) (M = Mn, Ni, Co) assemblies constructed by covalent and noncovalent interactions: uncommon coordination modes of methylpyrazoles and magnetic properties.

Two mononuclear complexes [Mn(5-methylpyrazole)4(N3)2] (1) and [Ni(5-methylpyrazole)4(N3)2] (2), as well as a novel one-dimensional coordination polymer [Co(3-methylpyrazole)2(5-methylpyrazole)2(tp)]n (3) (tp = terephthalate), were characterized. The isostructural complexes, 1 and 2, display two-dimensional supramolecular networks formed by hydrogen bonds between the N-H groups of 5-methylpyrazoles and the end N atoms of the azide ligands and additional face-to-face pi-pi interactions of the 5-methylpyrazoles. For 3, tp-bridged one-dimensional chains assisted by intrachain hydrogen bonds among the N-H groups of methylpyrazoles and carboxylate oxygens are connected with the help of interchain C-H...O hydrogen bonds, leading to a two-dimensional structure. The intra- and interchain hydrogen bonds account for the coexistence of two unique coordination forms (5-methylpyrazole and 3-methylpyrazole) of methylpyrazoles in the same coordination sphere. Weak antiferromagnetic interactions coupled with the spin-orbit coupling effect are operative in 3 through the tp ligands.

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PubMed2005

Cyanide-bridged W(V)-Mn(II) bimetallic double-zigzag chains with a metamagnetic nature.

A cyanide-bridged W-Mn bimetallic compound [W(CN)(6)(bpy)](2)[Mn(H(2)O)(2)].4H(2)O (1) (bpy = 2,2'-bipyridine) with a one-dimensional, crossed double-zigzag chain structure was prepared by self-assembling [W(CN)(6)(bpy)](-) and Mn(2+) ions in a 2:1 reaction ratio. The magnetic properties of 1 exhibit a field-induced metamagnetic behavior.

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PubMed2005

Cyano-bridged CuII-MV (M = Mo, W) bimetallic layered complexes exhibiting novel honeycomblike structures.

Self-assembly of a new precursor [Cu(L)](ClO4)2 (1) (L = macrocyclic ligand) with octacyanometalates [M(CN)8]3- (M = Mo, W) produced two-dimensional cyano-bridged Cu(II)-M(V) bimetallic assemblies [Cu(L)]3n[M(CN)8]2n.6nH2O [M = Mo (2), W (3)] with novel honeycomblike structures, characterized by spectroscopic data, single-crystal X-ray diffraction studies, and magnetic measurements. The crystallographic determination reveals that compounds 2 and 3 are isostructural and crystallize in the triclinic system (P). The Cu atom in a distorted octahedral environment experiences a tetragonal elongation of apical nitrogen atoms exhibiting average Cu-Nax lengths of 2.566 Angstroms for 2 and 2.593 Angstroms for 3, which accounts for the Jahn-Teller effect of a Cu(II) ion. The Cu-NC angles are magnetically important, ranging from 135.7 to 159.2 degrees. Three types of L in the crystal lattice are observed, which are dependent on the relative positions of the pendant hydroxyl groups with respect to the CuN4 basal plane. The positions are correlated with hydrogen bonding of OH groups to neighboring atoms. The magnetic data indicate that ferromagnetic and antiferromagnetic interactions between Cu(II) and M(V) through the CN linkage coexist.

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PubMed2005

Novel examples of high-dimensional mixed-valence copper cyanide complexes.

The first examples of high-dimensional mixed-valence homometallic cyano-bridged copper complexes were synthesized and characterized: net-structured [Cu(CN)(4){Cu(cyclam)}(1.5)](2)(n)()(H(2)O)(5)(n) (1), ladder-type double-chain-structured [Cu(CN)(2){Cu(CN)(2)Cu(cyclam)}](n)()(H(2)O)(n) (2), layer-structured [{Cu(CN)(2)}(2)Cu(cycalm)](n) (3), and hydrogen-bond-based 2-D [Cu(CN)(3)Cu(cyclam)](n)()(CH(3)OH)(n) (4) (cyclam = 1,4,8,11-tetraazacyclotetradecane). (1) Crystallizes in triclinic space group P with a = 8.3589(11) A, b = 13.478(2) A, c = 14.828(2) A, alpha = 66.895(2) degrees , beta = 77.916(3) degrees , gamma = 85.939(3) degrees , and Z = 1; (2) crystallizes in triclinic space group P with a = 8.2305(12) A, b = 9.8861(15) A, c = 13.219(2) A, alpha = 84.863(3) degrees , beta = 75.744(3) degrees , gamma = 89.818(3) degrees , and Z = 2; 3 crystallizes in monoclinic space group P2(1)/c with a = 6.830(2) A, b = 8.482(2) A, c = 17.306(4) A, beta = 98.144(4) degrees , and Z = 2; 4 crystallizes in triclinic space group P with a = 9.470(1) A, b = 10.034(1) A, c = 12.064(1) A, alpha = 67.325(2), beta = 75.593(2), gamma = 70.672(2), and Z = 2. The coordination sphere of Cu(I) sites in the complexes shows diverse structures: tetrahedral [CuC(4)] for (1), tetrahedral [CuC(3)N] and triangular [CuC(2)N] for (2), triangular [CuC(2)N] for (3), and triangular [CuC(3)] for 4. In particular, (1) constitutes the first example of a structurally characterized system containing a bridging tetrahedral [Cu(CN)(4)](3)(-) unit. The diverse structural nature of these complexes is governed by the capping amines and the content of water in the reaction media. The magnetic interactions are negligible in these mixed-valence complexes.

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PubMed2004

One-dimensional octacyanomolybdate-based Cu(II)--Mo(V) bimetallic assembly with a novel rope-ladder chain structure.

A new type of one-dimensional cyanide-bridged Cu(II)--Mo(V) bimetallic assembly, [Cu(cyclam)](3)[Mo(CN)(8)](2)x5H(2)O (cyclam = 1,4,8,11-tetraazacyclotetradecane), was prepared by self-assembling Mo(CN)(8)(3)(-) and Cu(cyclam)(2+) ions in a 2:3 stoichiometric ratio. The overall molecular view is delineated as a novel rope-ladder chain structure. It displays a dominant ferromagnetic behavior within a pentanuclear Cu(3)Mo(2) unit (J(p) = 3.88 cm(-)(1)). Interunit ferromagnetic interactions (J(c) = -0.03 cm(-)(1)) through a longer magnetic pathway of Cu--Mo and weak antiferromagnetic couplings (zJ' = -0.46 cm(-)(1)) resulting from interchain interactions are obtained.

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PubMed1999

High-Dimensional Manganese(II) Compounds with Noncovalent and/or Covalent Bonds Derived from Flexible Ligands: Self-Assembly and Structural Transformation.

A hydrogen- and covalent-bonded 3D array, [Mn(bpe)(H(2)O)(4)](n)()(ClO(4))(2)(n)()(bpe)(4)(n)()(H(2)O)(2)(n)() (2) [bpe = 1,2-bis(4-pyridyl)ethane], a covalent-bonded 3D network, [Mn(bpe)(1.5)(H(2)O)(tp)](n)()(H(2)O)(n)() (3) [tp = terephthalate], and a covalent-bonded 2D sheet, [Mn(bpe)(N(3))(2)](n)() (4), have been synthesized and characterized by spectroscopic data and single-crystal X-ray diffraction studies. Complex 2 contains two types of packing bpe molecules: One type of bpe molecules (=N31-bpe and symmetry-related bpe) run along the chain direction, and the other type of bpe molecules (=N11-bpe and N21-bpe) are slanted to the chain linked by bridging bpe (=N1-bpe). The chain is coupled with hydrogen bonds via N31-bpe, while hydrogen bonds through packing bpe molecules of N11- and N21-bpe sew the chains, leading to a 3D interlocking network structure. The bpe ligands in 3 have an anti conformation for the bridging bpe and a gauche conformation for the capping bpe with a dihedral angle between the two pyridyl rings of 44.5 degrees. The tp ligand acts as a linker of three metal ions through the unidentate and bridging modes, leading to the formation of a 2D layer. The final molecular dimensionality in 3 is determined from adding bpe ligands to the 2D sheet connected by tp ligands, resulting in a covalent-bonded 3D array where the bridging bpe ligands link the tp-bridged layers. The manganese(II) center in 4 consists of four equatorial azido nitrogen atoms and two axial bpe nitrogen atoms. The one-dimensional chains formed by two azido bridging ligands are interconnected by bpe ligands, each of which has two pyridyl rings with a dihedral angle of 67 degrees, leading to a two-dimensional sheet. Variable-temperature magnetic susceptibility data of 2 and 4 have been fitted to the infinite-chain model (H = -J summation operatorS(A)(i)().S(A)(i)()(+1)) derived by Fisher under the molecular field approximation (J '). Obtained exchange parameters are J = -0.083 cm(-)(1), g = 2.0 for 2 and J = -12.5 cm(-)(1), g = 2.0, J ' = 1.3 cm(-)(1) for 4. In the case of 3, the magnetic nature was interpreted by the dimer model (H = -JS(1).S(2)), affording parameters J = -0.96 cm(-)(1), g = 1.99, J ' = -0.005 cm(-)(1). MO calculations on a hypothetical dimeric unit (NH(3))(5)Mn-bpe-Mn(NH(3))(5) are discussed to evaluate the magnetic nature for the bpe-bridged system 4.

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