Xiang-Gao Meng

Multifunctional amino-decorated metal–organic frameworks: nonlinear-optic, ferroelectric, fluorescence sensing and photocatalytic properties

Solvothermal reactions of 2-amino-1,4-benzene dicarboxylic acid (NH2bdcH2) and N-auxiliary ligands in the presence of manganese(II), zinc(II) and cobalt(II) salts have given rise to four new metal–organic frameworks, namely, [Mn5(NH2bdc)5(bimb)5·(H2O)0.5]n (bimb = 4,4′-bis(1-imidazolyl)biphenyl) (1), [Zn(NH2bdc)(bix)·(DMF)2]n (bix = 1,4-bis(imidazol-1-ylmethyl)benzene) (2), [Co(NH2bdc)(bix)·(DMF)·(CH3CH2OH)]n (3) and [Co(NH2bdc)(bpp)]n (4) (bpp = 1,3-bis(4-pyridyl)propane). Single-crystal X-ray diffraction analyses revealed that MOF 1 displays 5-fold interpenetrating 4-connected dia 3D net; MOFs 2 and 3 are isomorphic, which possess 3-fold interpenetrating dia 3D nets; MOF 4 exhibits 4-connected sql 2D net. Noncentrosymmetric structures and multifunctionality in 1–3 are established by varying ligands and metal centers. In the solid state, polar MOFs 1–3 exhibit nonlinear-optic (NLO) and MOF 1 demonstrates typical ferroelectric behaviour with a remnant electric polarization (Pr) of 1.2 μC cm−2 and an electric coercive field (Ec) of 0.35 kV cm−1. In addition, MOF 2 could be a potential luminescent probe for detecting nitrobenzene or 2-nitrotoluene via fluorescence enhancement and has been evaluated as a promising visible-light-driven photocatalyst for degradation of organic pollutants.

Syntheses, Molecular Structures, Electrochemical Behavior, Theoretical Study, and Antitumor Activities of Organotin(IV) Complexes Containing 1-(4-Chlorophenyl)-1-cyclopentanecarboxylato Ligands

The organotin(IV) compounds [Me(2)Sn(L)(2)] (1), [Et(2)Sn(L)(2)] (2), [(n)Bu(2)Sn(L)(2)] (3), [(n)Oct(2)Sn(L)(2)] (4), [Ph(2)Sn(L)(2)] (5), and [PhOSnL](6) (6) have been synthesized from the reactions of 1-(4-chlorophenyl)-1-cyclopentanecarboxylic acid (HL) with the corresponding diorganotin(IV) oxide or dichloride. They were characterized by IR and multinuclear NMR spectroscopies, elemental analysis, cyclic voltammetry, and, for 2, 3, 4 and 6, single crystal X-ray diffraction analysis. While 1-5 are mononuclear diorganotin(IV) compounds, the X-ray diffraction of 6 discloses a hexameric drumlike structure with a prismatic Sn(6)O(6) core. All these complexes undergo irreversible reductions and were screened for their in vitro antitumor activities toward HL-60, BGC-823, Bel-7402, and KB human cancer cell lines. Within the mononuclear compounds, the most active ones (3, 5) are easiest to reduce (least cathodic reduction potentials), while the least active ones (1, 4) are the most difficult to reduce. Structural rearrangements (i.e., Sn-O bond cleavages and trans-to-cis isomerization) induced by reduction, which eventually can favor the bioactivity, are disclosed by theoretical/electrochemical studies.

Formation of unsymmetrical 1,4-enediones via a focusing domino strategy: cross-coupling of 1,3-dicarbonyl compounds and methyl ketones or terminal aryl alkenes.

A highly efficient synthesis of unsymmetrical 1,4-enediones from 1,3-dicarbonyl compounds and methyl ketones or terminal aryl alkenes has been developed via a focusing domino strategy. Simple and readily available starting materials, mild reaction conditions, and a very simple operation are advantages of the reaction, which allow straightforward synthesis of a variety of unsymmetrical 1,4-enediones.

Dinuclear copper(II) complexes of a polybenzimidazole ligand: their structures and inductive roles in DNA condensation.

The structures of two dinuclear Cu(II) complexes of dtpb were determined. They are shown to be capable of inducing DNA condensation into nanometer- and micrometer-scale particles under neutral conditions.

Dinuclear metal(II) complexes of polybenzimidazole ligands as carriers for DNA delivery.

A metal-based nonviral carrier for DNA-transfer in gene therapy was synthesized and characterized. The strong intermolecular pi-pi contacts are common in the observed dinuclear Cu(2+) and Co(2+) complexes of polybenzimidazole ligands. The affinity assays indicated that the strong binding of the complexes to DNA is driven by both electrostatic attractions between the complexes and DNA and the intercalation of the ligands between DNA base pairs. The typical in vitro studies showed that micromolar doses of each complex tested can efficiently and rapidly condense free DNA, either in linear or circular state, from solutions into well defined and globular nanoparticles with varied sizes. Therefore, the formation and dissociation of the DNA condensates were explored in detail under different conditions, indicating that the sizes of DNA condensates can be regulated by changing both doses and incubation time for the different dinuclear complexes. Since the intermolecular pi-pi interactions in the DNA-bound complexes may be a key force to drive DNA condensation, we propose a new DNA condensation model that is essentially distinct from that proposed for the most studied multivalent cationic reagents used in DNA condensation. The cellular uptake experiments successfully performed with the DNA condensates including plasmid pGL3 control vector that strongly expresses luciferase in many types of mammalian cells, as well as cytotoxicity evaluation, demonstrated the potentiality of the dinuclear metal(II) complexes as a new nonviral gene carrier. Finally, the dinuclear Co(2+) complexes of polybenzimidazole ligands are suggested to be the most potential nonviral gene carriers that are not impacted by serum proteins.

Two- and Three-Dimensional Silver(I)-Organic Networks Generated from Mono- and Dicarboxylphenylethynes

Three phenylethynes bearing methyl carboxylate (HL1), monocarboxylate (H(2)L2), and dicarboxylate (H(2)L3) groups were utilized as ligands to synthesize a new class of organometallic silver(I)-ethynide complexes as bifunctional building units to assemble silver(I)-organic networks. X-ray crystallographic studies revealed that in [Ag(2)(L1)(2)·AgNO(3)](∞) (1) (L1= 4-C(2)C(6)H(4)CO(2)CH(3)), one ethynide group interacts with three silver ions to form a complex unit. These units aggregate by sharing silver ions with the other three units to afford a silver column, which are further linked through argentophilic interaction to generate a two-demensional (2D) silver(I) network. In [Ag(2)(L2)·3AgNO(3)·H(2)O](∞) (2) (L2 = 4-CO(2)C(6)H(4)C(2)), the ethynide group coordinates to four silver ions to form a building unit (Ag(4)C(2)C(6)H(4)CO(2)), which interacts through silver(I)-carboxylate coordination bonds to generate a wave-like 2D network and is subsequently connected by nitrate anions as bridging ligands to afford a three-demensional (3D) network. In [Ag(3)(L3)·AgNO(3)](∞) (3) (L3 = 3,5-(CO(2))(2)C(6)H(3)C(2)), the building unit (Ag(4)C(2)C(6)H(3)(CO(2))(2)) aggregates to form a dimer [Ag(8)(L3)(2)] through argentophilic interaction. The dimeric units interact through silver(I)-carboxylate coordination bonds to directly generate a 3D network. The obtained results showed that as a building unit, silver(I)-ethynide complexes bearing carboxylate groups exhibit diverse binding modes, and an increase in the number of carboxylate groups in the silver(I)-ethynide complex unit leads to higher level architectures. In the solid state, all of the complexes (1, 2, and 3) are photoluminescent at room temperature.

3D coordination networks based on supramolecular chains as building units: synthesis and crystal structures of two silver(I) pyridyldiethynides.

Two silver(I) pyridyldiethynides, [Ag2(3,5-C2PyC2).4CF3CO2Ag.4H2O] ( A) and [Ag 2(3,5-C2PyC2).3AgNO3.H2O](B), were synthesized by reactions of 3,5-diethynylpyridine with silver trifluoroacetate and silver nitrate in high yield, respectively. X-ray crystallographic studies revealed that in A pyridyldiethynide groups connect Ag 11 cluster units to generate 1D supramolecular chains as bridging ligands, where each ethynide group interacts with four silver atoms. These supramolecular chains bearing pyridyl groups are linked by silver ions to form wavelike layers, which are further connected by trifluoroacetate ligands to afford a 3D coordination network. However, B exhibits a different structural feature, where two ethynide groups in one pyridyldiethynide ligand coordinate to three and four silver atoms, respectively. These silver ethynide cluster units are linked through silver-ethynide and argentophilic interactions, leading to a double silver chain by sharing silver atoms in these units. In B, the silver double chains are further connected by bridging pyridyldiethynide groups to generate 2D networks, which interact through the Ag-N coordination bonds between silver atoms and pyridyl groups in the adjacent layers to generate a 3D coordination network. In these two compounds, trifluoroacetate and nitrate groups exhibit different bonding modes, indicating that the counterion is an important factor influencing the structures of supramolecular chains and coordination networks.

Supramolecular Rhombic Grids Formed from Bimolecular Building Blocks

A programmed assembly process produces rhombic grid networks from compounds L1-L4 in the crystal by pi-pi stacking interactions that generate a bimolecular grid synthon, which undergoes further NH...N hydrogen-bond-mediated assembly.

Conformational Tuning of the Intramolecular Electronic Coupling in Molecular-Wire Biruthenium Complexes Bridged by Biphenyl Derivatives

The synthesis and characterization of a series of biphenyl-derived binuclear ruthenium complexes with terminal {RuCl(CO)(PMe3)3} moieties and different structural arrangements of the phenyl rings are reported. Electrochemical studies revealed that the two metal centers of the binuclear ruthenium complexes interact with each other through the biphenyl bridge, and the redox splittings ΔE1/2 show a strong linear correlation with cos(2)  ϕ, where ϕ is the torsion angle between the two phenyl rings. A combination of electrochemical, UV/Vis/NIR, and in situ IR differential spectroelectrochemical analysis clearly showed that: 1) the intramolecular electronic couplings in the binuclear ruthenium complexes could be modulated by changing ϕ; 2) the electronic ground state of the mixed-valent cations changes from delocalized to localized through the biphenyl bridge with increasing torsion angle ϕ, that is, the redox processes of these complexes change from significant involvement of the bridging ligand to an oxidation behavior with less participation of the bridge.

Syntheses, crystal structures and luminescence of two isostructural coordination polymers constructed from 4,5-imidazoledicarboxylate

The syntheses, IR, molecular structures, and luminescence of [M(HIMDC)(4, 4′-bipyO)0.5(H2O)] n [H3IMDC = 4, 5-imidazoledicarboxylate, 4, 4′-bipyO = 4, 4′-bipyridine-N, N′-dioxide, M = Co (1) and Zn (2)] are reported. The most notable structure feature of 1 and 2 is that the left-handed and right-handed helical chains constructed from 4,5-imidazoledicarboxylate and metal are linked by 4,4′-bipyO to generate infinite 2-D herringbone architectures. 2 exhibits strong fluorescent emission in the solid state at room temperature.