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Bei-Sheng Kang

Publications and source records attributed to Bei-Sheng Kang.

10 recordsLinked to original sources
PubMed2005

3D coordination polymers with nitrilotriacetic and 4,4'-bipyridyl mixed ligands: structural variation based on dinuclear or tetranuclear subunits assisted by Na-O and/or O-H...O interactions.

The reactions of Cu(II) with the mixed nitrilotriacetic acid (H3NTA) and 4,4'-bipyridyl (4,4'-bpy) ligands in different metal-to-ligand ratios in the presence of NaOH and NaClO4 afforded two complexes, Na3[Cu2(NTA)2(4,4'-bpy)]ClO4 x 5H2O (1) and [Cu2(NTA) (4,4'-bpy)2]ClO4 x 4H2O (2). The two complexes have been characterized by elemental analysis, IR, XRD, and single-crystal X-ray diffraction. 1 contains a basic doubly negatively charged [Cu2(NTA)2(4,4'-bpy)]2- dinuclear unit which was further assembled via multiple Na-O and O-H...O interactions into a three-dimensional (3D) pillared-layer structure. 2 features a two-dimensional (2D) undulated brick-wall architecture containing a basic doubly positively charged [Cu4(NTA)2(4,4'-bpy)2]2+ tetranuclear unit. The 2D network possesses large cavities hosting guest molecules and was further assembled via O-H...O hydrogen bonds into a 3D structure with several channels running in different directions.

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PubMed2005

A noninterpenetrated 1D molecular ladder and 2D butterfly network: effect of positional isomerism of semirigid bis(pyridylmethyl)pyromellitic diimide ligands on the architecture of their metal(II) complexes.

Three new complexes [Cd(4-pmpmd)1.5 (NO3)2] x CHCl3 (1), [Cd(3-pmpmd)1.5 (NO3)2] x EtOH (2), and [Zn(3-pmpmd)1.5 (NO3)2] x MeOH (3) (3- or 4-pmpmd = N,N'-bis(3- or 4-pyridylmethyl)pyromellitic diimide) containing T-shaped building blocks have been obtained from reactions between the long semirigid ligands 3- or 4-pmpmd and either cadmium or zinc nitrate. 1 forms noninterpenetrated 1D molecular ladders that are linked via multiple, complementary intermolecular C-H...O hydrogen bonds that effect the 3D alignment. 2 and 3 are isostructural and feature a noninterpenetrated 2D butterfly-shaped network with (6,3) topology. Multiple intermolecular C-H...O hydrogen bonds exist between the 2D layers and generate the 3D framework. The structural differences between 1 and 2 or 3 are attributed to the different conformations adopted by the ligands, which illustrate the influence of positional isomerism on the resultant supramolecular architectures of metal complexes.

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PubMed2003

Multidimensional frameworks assembled from silver(I) coordination polymers containing flexible bis(thioquinolyl) ligands: role of the intra- and intermolecular aromatic stacking interactions.

The two flexible multidentate ligands 1,3-bis(8-thioquinolyl)propane (C3TQ) and 1,4-bis(8-thioquinolyl)butane (C4TQ) were reacted with AgX (X = CF(3)SO(3)(-) or ClO(4)(-)) to give four new complexes: ([Ag(C3TQ)](ClO(4)))(n)() 1, ([Ag(C3TQ)](CF(3)SO(3)))(n)() 2, ([Ag(2)(C4TQ)(CF(3)SO(3))(CH(3)CN)](CF(3)SO(3)))(n)() 3, and ([Ag(C4TQ)](ClO(4)))(n)() 4. All complexes have been characterized by elemental analysis, IR, and (1)H NMR spectroscopy. Single-crystal X-ray analysis showed that chain structures form for all complexes in which the quinoline rings interact via various intra- (1) or intermolecular (2, 3, and 4) pi-pi aromatic stacking interactions, which in the latter cases results in multidimensional structures. Additional weak interactions, such as Ag.O and Ag.S contacts and C-H.O hydrogen bonding, are also present and help form stable, crystalline materials. It was found that the (CH(2))(n) spacers (n = 3 or 4) affect the orientation of the two terminal quinolyl rings, thereby significantly influencing the specific framework structure that forms. If the same ligand is used, on the other hand, then the different counteranions have the greatest effect on the final structure.

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PubMed2003

Syntheses, crystal structures, and luminescent properties of lanthanide complexes with tripodal ligands bearing benzimidazole and pyridine groups.

Two tripodal ligands, bis(2-benzimidazolylmethyl)(2-pyridylmethyl)amine (L(1)) and bis(2-pyridylmethyl)(2-benzimidazolylmethyl)amine (L(2)), were synthesized. With the third chromophoric ligand antipyrine (Antipy), three series of lanthanide(III) complexes were prepared: [LnL(1)(Antipy)(3)](ClO(4))(3) (series A), [LnL(1)(Antipy)Cl(H(2)O)(2)]Cl(2)(H(2)O)(2) (series B), and [LnL(2)(NO(3))(3)] (series C). The nitrate salt of the free ligand H(2)L(1).(NO(3))(2) and six complexes were structurally characterized: Pr(3+)A, Y(3+)A, Eu(3+)B, Eu(3+)C, Gd(3+)C and Tb(3+)C, in which the two A and three C complexes are isomorphous. Crystallographic studies showed that tripodal ligands L(1) and L(2) exhibited a tripodal coordination mode and formed 1:1 complexes with all lanthanide metal ions. The coordination numbers of the lanthanide metal ions for the A, B, and C complexes were 7, 8, and 10, respectively. Conductivity studies on the B and C complexes in methanol showed that, in the former, the coordinated Cl(-) dissociated to give 3:1 electrolytes and, in the latter, two coordinated NO(3)(-) ions dissociated to give 2:1 electrolytes. Detailed photophysical studies have been performed on the free ligands and their Gd(III), Eu(III), and Tb(III) complexes in several solvents. The results show a wide range in the emission properties of the complexes, which could be rationalized in terms of the coordination situation, the (3)LC level of the complexes, and the subtle variations in the steric properties of the ligands. In particular the Eu(3+)A and Tb(3+)A complexes, in which the central metal ions were wholly coordinated by chromophoric ligands of one L(1) and three antipyrine molecules, had relatively higher emission quantum yields than their corresponding B and C complexes.

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PubMed2003

Formation of racemate and mesocate complexes from an achiral tripodal ligand containing three benzimidazole groups.

Two complexes of the achiral tripodal ligand tris(1-benzimidazolylethyl)amine (nteb), viz., [Mn(nteb)(2)(H(2)O)(2)](ClO(4))(2).CH(3)OH, 1, and [Ag(2)(nteb)(2)](CF(3)CO(2))(2).2H(2)O, 2, have been synthesized and characterized by IR, (1)H NMR, and EPR spectroscopy (1), electrospray mass spectrometry, thermogravimetric analysis, and X-ray crystallography. Compound 1 contains chiral complex cations due to the same handedness of two nteb ligands (deltadelta or lambdalambda) but crystallizes as a racemate, while 2 contains a dinuclear mesocate because of the opposite handedness (deltalambda) of two nteb ligands. Crystal data for 1: space group P(-)1 with a = 9.471(4) A, b = 16.884(7) A, c = 19.906(8) A, alpha = 77.930(7) degrees, beta = 88.063(7) degrees, gamma = 89.706(7) degrees, V = 3111(2) A(3), and Z = 2. Crystal data for 2: space group P(-)1 with a = 9.3390(12) A, b = 10.2168(13) A, c = 16.382(2) A, alpha = 75.721(3) degrees, beta = 87.857(3) degrees, gamma = 71.738(3) degrees, V = 1437.2(3) A(3), and Z = 1. In 1, water serves as an auxiliary ligand, connected to one imidazole N atom of each nteb ligand through a H-bridge; the cationic complexes are associated intermolecularly via pi.pi interactions. In contrast to 1, the coordination to the Ag(+) ions in 2 occurs in a heterochiral manner and produces a dinuclear mesocate.

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PubMed1998

3D Extended Supramolecular Structures via H-Bonded Linkages of 2D Sheetlike or 1D Zigzag Coordination Polymers.

Two 3D supramolecular complexes [Cu(2)(trans-oxpn)(phth)](n)().2nH(2)O, 1, and [Cu(2)(trans-oxpn)(&mgr;-OH)(&mgr;-H(2)O)](n)()Br(n)().2nH(2)O, 2 [H(2)oxpn = N,N'-bis(3-aminopropyl)oxamide, phth = phthalate], were synthesized and characterized by single-crystal X-ray crystallography, thermal analyses, and magnetic measurements. 1 crystallizes in the monoclinic space group P2(1)/c with a = 8.578(2) Å, b = 15.596(2) Å, c = 15.657(2) Å, beta = 101.29(2) degrees, Z = 4; 2 crystallizes in the trigonal space group R&thremacr;c with a = 15.266(2) Å, b = 15.266(2) Å, c = 34.953(5) Å, and Z= 18. The neutral 2D sheetlike coordination polymer [Cu(2)(trans-oxpn)(phth)](n)() in 1 contains alternate trans-oxamidate and phthalate bridges and then is joined together by H(2)O molecules via the hydrogen bond linkage Cu(oxpn).H(2)O.H(2)O.(oxpn)Cu to produce a 3D supramolecular structure. The cationic chains [Cu(2)(trans-oxpn)(&mgr;-OH)(&mgr;-H(2)O)](n)()(n)()(+) in 2 contain alternate trans-oxamidate, &mgr;-OH, and &mgr;-H(2)O bridges and are arranged in three directions, intersecting with one another to yield an extended network via the interchain hydrogen bonds formed by metal-coordinated OH(-) with the linkages Cu(oxpn)-OH.OH-Cu(oxpn). Magnetic calculations showed the presence of antiferromagnetic exchange interactions for both complexes. The 2D magnetic coupling system of 1 was simplified into interacting dimers Cu(trans-oxpn)Cu, with the coupling via phth as an interdimer interaction and the data were interpreted with a modified Bleaney-Bowers equation leading to J = -456.7 cm(-)(1) and theta = 22.0 K. 2 was analyzed qualitatively by an alternating chain model taking into account the interchain interaction in a molecular model with J(1) = -309.6 cm(-)(1), J(2) = -63.5 cm(-)(1), and theta = -12.9 K, where J(1) and J(2) denote the coupling constants of the bridges oxamidate and &mgr;-OH, respectively.

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