Ben-Lai Wu

Construction and isomeric transformation of polyoxometalates directed by 1,ω-bis(pyridinium)alkane templates

Ten novel inorganic–organic hybrid polyoxometalates, namely, [1,3-bis(pyridinium) propane]2[α-Mo8O26] (1), [1,4-bis(pyridinium)butane]2[1D-Mo8O26] (2), [1,5-bis(pyridinium)pentane]2[θ-Mo8O26] (3), [1,6-bis(pyridinium)hexane]2[1D-Mo8O26] (4), [1,7-bis(pyridinium)heptane]2[β-Mo8O26] (5), [1,8-bis(pyridinium)octane]2[θ-Mo8O26] (6), [1,9-bis(pyridinium)nonane]2[(α + β)-Mo8O26] (7), [1,10-bis(pyridinium)decane]2[β-Mo8O26] (8), [1,11-bis(pyridinium)undecane]2[β-Mo8O26] (9), [1,12-bis(pyridinium)dodecane]2[γ-Mo8O26] (10), (Scheme 1) were synthesized by cation templated self-assembly with octamolybdate anions under hydrothermal reaction conditions. Crystal data analysis revealed that these compounds were all composed of discrete organic cations and polyacid anions [Mo8O26]4− interacting by electrostatic and hydrogen bond interactions. Interestingly in these compounds the anion fraction could take on α-, β-, θ-, γ-[Mo8O26]4− 0D isomers or rare 1D- polymeric frameworks with a simple length modification of the alkane components. Moreover, these polyacid compounds had definite catalytic activities on the oxidation reaction of acetaldehyde to acetic acid and the relationship of structure/catalytic activities were initially demonstrated.

Homochiral coordination polymers with distorted helices consisting of achiral ligand

Reactions of achiral ligand N2,N6-bis((pyridin-2-yl)methyl)pyridine-2,6-dicarboxamide (L) with AgAsF6 and AgSbF6, respectively, produced [AgL] n · nAsF6 (1) and [AgL] n · nSbF6 (2), where helically chiral 1-D coordination polymers conglomerate through complicated supramolecular interactions to form two 3-D enantiomerically chiral architectures with unusual (10,3) nets, showing spontaneous chiral resolution. Compounds 1 and 2 emit ligand-centered violet-fluorescence with strong intensities and double peaks centered at 329 and 344 nm.

Unique Tetradentate Coordination of 2,2′-Bipyridyl-3,3′-Dicarboxylate (bpdc). Hydrothermal Synthesis and Crystal Structure of A Novel Polymeric Supramolecule [Co(bpdc)(H2O)2]n

The title complex has been synthesized using hydrothermal methods and its structure determined by X-ray diffraction. It consists of polymeric chains of [Co(bpdc)(H2O)2] units (bpdc = 2,2′-bipyridyl-3,3′-dicarboxylate) which are linked by intermolecular hydrogen bonds to form two-dimensional layer-shaped supramolecules. Each bpdc ligand bridges two cobalt(II) centers in a rare tetradentate fashion through its two pyridyl nitrogen atoms chelating to one cobalt and two carboxyl oxygen atoms to the other in the equatorial plane. The octahedral coordination of cobalt is completed by two axial water molecules.

Counteranion's effects on the structures of supramolecular silver coordination compounds of one asymmetric and one biting organic ligands

Reactions of one asymmetric ligand 1,6-dihydro-2-methyl-6-oxo-(3,4′-bipyridine)-5-carbonitrile (L1) with AgX (X = NO3−, BF4−, AsF6−, SbF6−) afforded two 1-D interpenetrating coordination polymers {[Ag2(L1)3]2·(CH3OH)3·(AsF6)4}n (1) and {[Ag2(L1)3]2·(SbF6)4}n (2), and two monomers [Ag(L1)2]·(NO3) (3) and [Ag(L1)2]·(CH3OH) (BF4) (4). The structural similarity between compounds 1 and 2, and the structural difference between compounds 1 and 2 and compounds 3 and 4 give evidences that the sizes of counteranions with the same polyhedron sometimes can not affect the supramolecular structures, but the polyhedra of counteranions sometimes can. The self-assembly of one angular ligand 1,3,4-thiadiazole-2,5-di-2-pyridyl (L2) with AgX (X = BF4−, ClO4−, PF6−, AsF6−, NO3−, SbF6−) produced five di-nuclear and one mono-nuclear silver(I) coordination compounds. In the three dinuclear compounds [Ag2(L2)2](BF4)2 (5), [Ag2(L2)2](ClO4)2 (6), and [Ag2(L2)2](PF6)2 (7), there are medium Ag–Ag interactions between two adjacent dimers, leading to a 1-D supramolecular chain. In the other two dimers [Ag2(L2)2](AsF6)2 (8) and [Ag2(L2)2](NO3)2(CH3OH) (9), however, no Ag–Ag interactions were found. When changing counteranion to the very large one SbF6−, the silver complex of L2 is a monomer [Ag(L2)2](SbF6) (10). The supramolecular structural diversity of compounds 7, 8, and 10, resulting from the volume changes of the octahedral counteranions shows that the sizes of counteranions with the same polyhedron can sometimes affect the supramolecular structures.

Crystal structures and luminescence properties of two new terbium complexes with aromatic carboxylic acid

Two new terbium complexes with aromatic carboxylic acids, [(Tb)2(L1)6(H2O)4] (1) and [(Tb)2(L2)6(H2O)2(DMF)2] (2) (HL1: nicotinic acid; HL2: 4-hydroxybenzoic acid), with different coordination geometries have been synthesized and their crystal structures determined. The luminescence properties of the two complexes, including the phosphorescence lifetime, have been investigated. The effect of a secondary ligand on luminescence of the ternary terbium complex with carboxylic acid and the relationship between luminescence properties and crystal structure, including coordination mode of the carboxyl groups from HL1 and HL2 and coordination mode of a secondary ligand, are discussed.

Hydrothermal Synthesis, Crystal Structure, and Properties of Nickel(II) Coordination Polymer with 2,2′‐Bipyridyl‐3,3′‐dicarboxylate

Abstract The polymeric complex [Ni(bpdc)(H2O)2] n (bpdc, 2,2′‐bipyridyl‐3,3′‐dicarboxylate dianion) which consist of [Ni(bpdc)(H2O)2] units was synthesized using a hydrothermal method. Its crystal structure was determined by x‐ray crystal diffraction as 1‐D chain‐like polymer. In [Ni(bpdc)(H2O)2] n , each bpdc bridges a Ni(II) pair in a unique tetradentate fashion through its two pyridine nitrogen atoms and two oxygen atoms of two carboxyl groups. Each Ni(II) cation has a slightly distorted octahedral coordination environment where the equatorial plane includes the two nitrogen atoms of one bpdc ligand and two oxygen atoms of another bpdc anion, while the axial positions are occupied by two oxygen atoms of two coordinated water molecules. In the polymeric complex the complicated hydrogen‐bonding network and π–π stacking interaction play an important role for its thermostability.

trans-Diaqua­bis[5-carb­oxy-2-(3-pyrid­yl)-1H-imidazole-4-carboxyl­ato-κ2N3,O4]iron(II)

In the title complex, [Fe(C10H6N3O4)2(H2O)2], the FeII atom is located on an inversion centre and is trans-coordinated by two N,O-bidentate 5-carboxy-2-(3-pyridyl)-1H-imidazole-4-carboxylate ligands and two water molecules, defining a distorted octahedral environment. A two-dimensional network of N—H⋯O and O—H⋯O hydrogen bonds extending parallel to (110) helps to stabilize the crystal packing.

Synthesis, crystal structure and characterization of a 1D chain coordination polymer of zinc(II) with aroylamide, [Zn(H2bpb)Cl2] n · CH3OH, (H2bpb = 1,2- bis (3-pyridylcarboxamide)benzene)

A four-coordinate zinc(II) coordination polymer, [ZnCl2(H2bpb)] n · CH3OH (H2bpb = 1,2-bis(3-pyridylcarboxylamide)benzene), has been prepared and the crystal structure determined by X-ray diffraction. It crystallizes in the triclinic system, space group with a = 7.898(3) Å, b = 11.792(4) Å, c = 11.911(4) Å, α = 76.051(4)°, β = 89.919(4)°, γ = 78.267(4)°, V = 1052.9(7) Å, Z = 2. The crystal structure consists of chains of complex zig-zaging along the b lattice translation. Fluorescent and thermal properties of the complex were also investigated.

Complex [Cd(dafo)2(tphpo)(CH3COO)]ClO4 (dafo=4,5-diazafluoren-9-one, tphpo=triphenylphosphine oxide) with chiral metal centers. Helical packing induced by π–π stacking interactions of dafo rings

Abstract The first complex of 4,5-diazafluoren-9-one (dafo) and cadmium: [Cd(dafo)2(tphpo)(CH3COO)]ClO4 (triphenylphosphine oxide=tphpo) is a quaternary complex with chiral metal centers and crystallizes in a monoclinic cell with space group P2(1)/n. Cadmium centers with 7-fold coordination adopt a distorted monocapped trigonal prismatic geometry. Two oxygen atoms of acetate and one oxygen atom of triphenylphosphine oxide form the top triangle of the trigonal prism, while three nitrogen atoms from two dafo groups construct the bigger bottom triangle. The last nitrogen atom of dafo groups occupies the monocapped position. Here, dafo molecules display two different coordination patterns, namely unsymmetric and symmetric chelation. Moreover, the interesting linking of screw related cations is fabricated by inter-molecular π–π stacking interactions in the complex.

Two new 2-D coordination polymers based on a purine-containing carboxylate

A purine-containing multifunctional ligand, 2-(6-oxo-6H-purin-1(9H)-yl)acetic acid (HL), and two new 2-D coordination polymers, [Co(L)2(H2O)2] n · 2nH2O (1) and [Ni(L)2(H2O)2] n · 2nH2O (2), were synthesized and characterized. Polymers 1 and 2 have isomorphous structures with (4,4)-connected topologies composed of left- and right-handed metal–organic helices sharing common metal centers. Two helical conformations in the same net are stabilized by strong π–π stacking interactions between purine groups. Through direct and water-mediated interlayer hydrogen-bond interactions those layers are assembled into stable 3-D supermolecules where slight differences in the strength of hydrogen bonds and coordination bonds result in their decomposition behaviors.