Double Ligands Research Articles

Three Mn(II) complexes with 1,3-bis(4-pyridyl)propane and their supramolecular nets

Three complexes, [Mn(bpp)4(H2O)2](ClO4)2 · 1.5H2O (1), [Mn(bpp)3Br2] · 2H2O (2), and [Mn(bpp)2(H2O)2](ClO4) · I · H2O · bpp (3) (bpp = 1,3-bis(4-pyridyl)propane), were synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 is mononuclear where M(II) is coordinated to a monodentate TT-bpp, three monodentate TG-bpp, and two water molecules. Complex 2 possesses a single-stranded helical chain formed from MnN4Br2 octahedra by a single TT-bpp, with pendant monodentate TG-bpp ligands. Complex 3 consists of a ribbon-type double-stranded chain formed from MnN4O2 octahedra by double TG-bpp ligands. 2-D supramolecular architectures of 1–3 are formed by hydrogen bonds. The fluorescence of the three complexes comes from the π*–π transition of the ligand.

Mercury(II) Halide and Copper(I) Iodide Complexes of Double-Tweezer Ligand with Thiocyclohexyl End-Group

L Research on the multi-dentate ligand system for binuclear compounds is in great demand due to the prospect that such species may serve as models of electron transfer, charge transfer and allosteric behaviors observed in biochemical system. The structural topologies of the binucleating frameworks are often determined by arguments of donor system and organic linkers. Our group and others have reported a series of dinuclear complexes of macrocyclic ligands with discrete and continuous forms. Parallel to this, noncyclic podal ligand system often give the dinuclear complexes. A further possibility to prepare the dinuclear complexes with soft metals could be given by applying the multipodal ligands with sulfur donors in each arm. Recently, Hanton et al. and our group have reported a double tweezertype ligand with four thiopyridyl arms, [1,2,4,5-tetrakis(2pyridylmethylsufanylmethyl)benzene] which forms dinuclear complexes with Cu(II) and Cd(II) instead of a polymeric array due to the three-layered π-stacking motif. In this regard, we are interested in using a ligand-directed approach to construct new discrete dinuclear complexes as well as to achieve the construction of infinite coordination polymers. Thus, the double tweezer-type ligands with non-aromatic end-groups are of particular interest. The proposed quadru-armed ligand L employs one sulfur donor as a binding site and cyclohexane end-group in each arm which, in turn, will serve to minimize the interand/or intramolecular interactions. In this paper, we report dimercury(II) halide complexes [Hg2(L)X4] (X = Cl: 1a, X = Br: 1b, X = I: 1c) and copper(I) iodide coordination polymer [Cu2(L)I2]n of L which were structurally characterized by single-crystal X-ray analysis. The thermal properties and comparative NMR study of the complexes were also accomplished.

Syntheses and structures of three new coordination polymers with the flexible 1,4- bis (imidazol-1-yl)butane ligand

Three new coordination polymers [Co(bimb)2(NCS)2] n (1), {[Co(bimb)2(dca)2] · CH3CN} n (2) and [Cu(bimb)2(NO3)2] n (3) (bimb = 1,4-bis(imidazol-1-yl)butane, dca = dicyanamide) were synthesized and characterized. In 1, each Co(II) links two Co(II)'s by double bimb ligands and extends to form a one-dimensional chain containing the Co2(bimb)2 22-membered metallocycle. 2 and 3 are two-dimensional (4, 4) networks linked by bimb bridges. The conformations of the bimb ligands in 1, 2 and 3 are analyzed.

Synthesis, Structure and DNA Binding Properties of [Cu2(heae)(SCN)2] n · nH2O the First One-Dimensional Polymeric Copper(II) Complex Bridged Alternately by Oxamidate and Double End-to-End Thiocyanate Ligands

A new one-dimensional polymeric copper(II) complex, [Cu2(heae)(SCN)2] n · nH2O [H2heae is N,N′-bis(N-hydroxyethylaminoethyl)oxamide], has been synthesized and characterized by elemental analysis, molar conductivity measurement, IR and electronic spectra studies, and single-crystal X-ray diffraction. The structure of the complex exhibits a neutral one-dimensional polymeric copper(II) zigzag chain [Cu2(heae)(SCN)2] n constructed by μ-trans-heae and double μ-1,3-thiocyanate ligands. The environment about copper can be described as a square-pyramid. The neighboring second building units (SBUs), [Cu(trans-heae)Cu]2+, are unequal with Cu···Cu separations of 5.287 and 5.273 A for Cu1···Cu1i and Cu2···Cu2ii, respectively. The double thiocyanate ligands function as μ(1,3)-bridges to link these unequal SBUs thereby forming zigzag chains with a Cu1···Cu2 separation of 5.454 A. The hydrogen bonds in the crystal structure self-assemble the one-dimensional chains into a three-dimensional supramolecular structure. The interaction of the polymeric copper(II) complex with herring sperm DNA (HS-DNA) has been investigated by using absorption and emission spectra, electrochemical techniques and viscometry. The results reveal that the polymeric copper(II) complex interacts with HS-DNA via a groove binding mode with the intrinsic binding constant of 1.38 × 104 M−1. To the best of our knowledge, this is the first example about the structure and DNA-bonding studies of a one-dimensional polymeric copper(II) complex that is bridged alternately by trans-oxamidate and double-thiocyanate ligands.

Syntheses and structures of three manganese coordination polymers with 1,4- bis (imidazol-1-yl)butane

Three manganese coordination polymers [Mn(bimb)2(NCS)2] n (1), [Mn(bimb)2(dca)2] n (2) and [Mn(bimb)2(N3)2] n (3) (bimb = 1,4-bis(imidazol-1-yl)butane, dca = dicyanamide) were synthesized and characterized by X-ray crystallography, IR and thermogravimetric analysis. In 1 and 2, each Mn(II) links two Mn(II) atoms by double bimb ligands and extends to form a one-dimensional double chain structure containing the Mn2(bimb)2 22-member metallocycle. 3 constructs a two-dimensional (4,4) network linked by bimb bridges.

Enhanced effect of sulfonylurea (SU) in copolymer comprising a sugar moiety and SU derivative as double ligands on insulin secretion from MIN6 cells

Copolymers composed of sulfonylurea(SU) as an antagonist of ATP-sensitive K+ channel and sugar moieties as double ligands were synthesized. Insulin secretion from MIN6 cells(insulinoma cell line) in contact with the copolymers was evaluated. MIN6 cells attached to the poly(N-p-vinylbenzyl-D-maltonamide-co-SU) [P(VMA-co-SU)]-coated dishes were in the more aggregated form as compared to other polymer-coated surfaces. By introducing SU into the sugar bearing homopolymer, an enhanced effect on insulin secretion from MIN6 cells was observed due to the specific interaction between SU ligands and SU receptors on the β-cell membrane. P(VMA-coSU) composed of SU and non-reducing glucose moieties demonstrated enhanced insulin secretion from MIN6 cells and faster proliferation of MIN6 cells as compared to poly(N-p-vinylbenzyl-D-lactonamide-co-SU) [P(VLA-co-SU)] probably owing to the glucose transporters presence on the MIN6 cell membrane. Insulin secretion from MIN6 cells pretreated with diazoxide as an agonist of ATP-sensitive K+ channel was suppressed.

Formation of Nickel(II) Coordination Polymers by a Double Betaine: [{Ni(L)(H2O) 2} n] Cl2n.2nH2O and [{Ni(L)2(H2O)2} n

Two novel polymeric nickel(II) complexes of a double betaine with a rigidtris(ethylene) bridge between the pair of nitrogen atoms, namely [ {Ni(L)(H2O)4 }n]Cl2n.2nH2O(1)and [ {Ni(L)2(H2O)2} n](ClO4)2n.4nH2O(2) [L =¯O2CCH2N+(CH2CH2)3N+CH2CO2¯], have been prepared and characterized by X-ray crystallography. Thenickel(II) atom in either complex is coordinated by unidentate carboxylategroups and aqua ligands in a distorted octahedral geometry. The crystalstructure of (1) features an infinite zigzag chain composed of an alternatearrangement of metal atoms and double betaine ligands, and hydrogen bondingamong adjacent chains leads to a three-dimensional network. Complex (2)exhibits a wave-like layer structure corresponding to the (2 0 0) family ofplanes.

Formation of copper(II) coordination polymers by a flexible double betaine: [{Cu(L)X2(H2O)} n ]·2nH2O [X=Cl, Br] and [{Cu(L)(H2O)4} n ](ClO4)2n ·2nH2O [L=−O2CCH (Me3N+)CH2CH2CH(Me3N+)CO 2 −

Three polymeric copper(II) complexes of a flexible double betaine, namely, [{Cu(L)Cl2(H2O)}n]·2nH2O (1), [{Cu(L)Br2(H2O)}n]·2nH2O (2), and [{Cu(L)(H2O)4}n](ClO4)2n·2nH2O (3) [L=−O2CCH(Me3N+)CH2CH2CH(Me3N+CO2], have been prepared and characterized by singlecrystal X-ray analysis. Isomorphous complexes (1) and (2) crystallize in space groupC2/c (No. 15) witha=17.725(3),b=5.958(2),c=19.077(3) A, β=110.70(1)o,V=1881.4(4) A3, Z=4 anda=18.268(4),b=5.948(3),c=19.166(5) A, β=109.08(2)o,V=1964.7(9) A3, Z=4, respectively. Complex (3) belongs to space groupPĪ (No. 2) witha=6.203(1),b=9.293(2),c=12.035(2) A, α=86.56(2), β=87.33(3), γ=71.23(2)o,V=655.4(2) A3 and Z=1. The crystal structure of (1) and (2) features an infinite zigzag chain composed of an alternate arrangement of metal atoms and double betaines ligands, with each Cu(II) atom in a distorted CuX2O3 [X-Cl, Br] square-pyramidal geometry, and hydrogen bonding between adjacent chains leads to a layer structure concentrated the (200) family of planes. Complex (3) exhibits a layer structure corresponding to the (001) family of planes, in which neighboring chains constructed from the metal atoms and the double betaine ligands are cross-linked by hydrogen bonding between the aqua ligands. The Cu(II) atom is coordinated in a CuO6 octahedral geometry with Jahn-Teller distortion.