Heterodimetallic compounds assembled from ferrocenedicarboxylato and ferrocenecarboxylato ligands

Heteropolynuclear organometallic compounds have been constructed by using two kinds of ferrocene-based ligands, 1,1'-ferrocenedicarboxylic acid (H(2)L(1)) and ferrocenecarboxylic acid (HL(2)). Reactions the ligand H(2)L(1) with copper(II) and nickel(II) salts, in the presence of pyridine, give a tetranuclear Cu(2)Fe(2) mixed-metallic box Cu(2)L(1)(2)(Py)(2)(DMF)(2)(H(2)O)(2) (1) and a tetranuclear heterobimetallic helix Ni(2)L(1)(2)(Py)(4)(H(2)O) (2), respectively. In these complexes, the ferrocene moieties show cisoid conformations which lead to the formation of the finite coordination geometry, i.e. to molecular complexes. Interactions of the ligand H(2)L(1) with lanthanide ions afford two-dimensional networks [La(2)L(1)(3)(CH(3)OH)(4)]( infinity ) (3), [Eu(2)L(1)(3)(H(2)O)(5)]( infinity ) (4), and [Gd(2)L(1)(3)(CH(3)OH)(2)(H(2)O)(3)]( infinity ) (5), respectively, in which transoid conformations of the ferrocene moiety provide opportunities to form infinite 2-D networks. It is suggested that the conformational freedom of the ferrocene moiety makes the ligand L(1) display different conformations and coordination modes in these complexes. In addition, the pi.pi interactions related to the ferrocene moieties were also found to stabilize the supramolecular architectures in the solid state. As a comparison, reaction of lanthanide ions with the ligand HL(2) resulted in three isostructural heterodinuclear windmill-shaped compounds Ln(2)L(2)(6)(CH(3)OH)(2)(H(2)O)(5) [Ln = La (6), Eu (7), and Gd (8)] by simply diffusing the solutions of lanthanide ions into the mixture of HL(2) and NaOH, respectively. Electrochemical properties of the ferrocene-containing complexes 1-8 are also investigated in the solution or solid state.     

Heterometallic Ln/Hg compounds with fluorinated thiolate ligands

The early lanthanide benzenefluorothiolates (Ln(SC(6)F(5))(3); Ln = La, Ce, Pr, Nd, Sm, Gd) react with Hg(SC(6)F(5))(2) in DME to form ionic heterometallic compounds with Ln cations and Hg anions. X-ray diffraction analyses of all compounds reveal an isostructural series with the general formula [(DME)(3)Ln(SC(6)F(5))(2)](2)[Hg(2)(SC(6)F(5))(6)]. In the structures, a fluorothiolate ligand has been extracted from the Ln coordination sphere that is saturated with three neutral DME donor ligands and a dative interaction between one ortho fluorine and the Ln. Distances between Ln and F do not vary simply with Ln ionic radius. There are two Ln cations with charge balanced by a Hg(2)(SC(6)F(5))(6) dianion composed of two distinctly nonideal Hg(II) tetrahedra, all connected through a series of pi-pi interactions that link cations with anions in a one-dimensional array and anions to anions in a more complex 2D network.     

Two new hybrid compounds assembled from Keggin-type polyoxometalates and transition metal coordination complexes

Two new hybrid compounds based on Keggin-type polyoxometalates: {[PMo₁₂O₄₀][Ni(Phen)₂(H₂O)]₂}·K·2OH⁻ (1) and [Cd₂(Phen)₄Cl₂][HPW₁₂O₄₀]·H₂O (2) (Phen=1,10-phenanthroline), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Compound 1 exhibits a 1-D chain structure constructed from Pseudo-Keggin polyoxometalate bi-supported transition metal coordination complexes linked by K⁺ ions. Compound 2 contains Pseudo-Keggin polyoxoanions [HPW₁₂O₄₀]²⁻ and novel metal-chloride-ligand coordination complexes [Cd₂(Phen)₄Cl₂]²⁺.     

Microsheets assembled from pyridinium-tailored anthracenes

A facile strategy to construct microsheets assembled from 9-substituted anthracene-pyridinium compounds (APs) has been developed. With the different length of linkers, APs could form the ‘v’-shaped dimer or ‘face-to-face’ dimer, respectively, driven by CH–π interactions and π-stacking interactions, which consequently lead to the assembly of final microsheets.     

Synthesis and characterization of redox-active coordination polymers generated from ferrocene-containing bridging ligands

Coordination polymers showing redox activity have been constructed by using ferrocene-based bidentate ligands, 1,1'-(4-dipyridinethio)ferrocene (1) and 1,1'-(2-dipyridinethio)ferrocene (2). The ligand of 1 formed an Ag(I) coordination polymer, 1 x AgPF(6) x (CH(3)CN)(2) (3). This complex showed a 1-D double-chain structure, with a weak interchain Ag...Ag interaction. Combination of 1 with M(hfac)(2) (M = Mn, Cu, Zn) afforded 1-D chain complexes, 1 x M(hfac)(2) (M = Mn (5), Cu (6), Zn (7)). The complex 2 x CuPF(6) (8) showed a 1-D twisted helix-like chain structure.     

Spontaneous resolution of chiral polyoxometalate-based compounds consisting of 3D chiral inorganic skeletons assembled from different helical units

Four enantiomerically pure 3D chiral POM-based compounds, [Ni(2)(bbi)(2)(H(2)O)(4)V(4)O(12)]2 H(2)O (1 a and 1 b) and [Co(bbi)(H(2)O)V(2)O(6)] (2 a and 2 b) (bbi=1,1'-(1,4-butanediyl)bisimidazole) based on the achiral ligand, different vanadate chains, and different metal centers have been synthesized by hydrothermal methods. Single-crystal X-ray diffraction analyses revealed that 1 a and 1 b, and 2 a and 2 b, respectively, are enantiomers. In 1 a and 1 b two kinds of vanadate chains with different screw axes link Ni cations to generate 3D chiral inorganic skeletons, which are connected by the achiral bbi ligands to form complicated 3D 3,4-connected chiral self-penetrating frameworks with (7(2)8)(7(2)8(2)9(2))(7(3)8(2)10) topology. They represent the first examples of chiral self-penetrating frameworks known for polyoxometalate (POM) systems. Contrary to 1 a and 1 b, in 2 a and 2 b the vanadate chains link Co(II) cations to generate 3D chiral inorganic skeletons, which are assembled from two kinds of heterometallic helical units of opposite chirality along the c axes. The chiral inorganic skeletons are connected by bbi to form 3D 3,4-connected chiral POM-based frameworks with (6(2)8)(2)(6(2)8(2)10(2)) topology. It is believed that the asymmetrical coordination modes of the metal cations in 1 a-2 b generate the initial chiral centers, and that the formation of the various helical units and the hydrogen bond interactions are responsible for preservation of the chirality and spontaneous resolution when the chirality is extended into the homochiral 3D-networks. This is the first known report of chiral POM-based compounds consisting of 3D chiral inorganic skeletons being obtained by spontaneous resolution upon crystallization in the absence of any chiral source, which may provide a rational strategy for synthesis of chiral POM-based compounds by using achiral ligands and POM helical units.     

Two new hybrid compounds assembled from Keggin phosphotungstates,cobalt/zinc cations and V-shaped imidazole ligands

Two new inorganic–organic hybrid compounds, [Co(H₂O)₂(bimb)₂]₂[PW^VW^VI₁₁O₄₀] (1) and [Zn₃(H₂O)₄(bimb)₄][PW^V₃W^VI₉O₄₀] (2) (bimb = 1,3-bis(1-imidazoly)benzene) have been obtained and characterized by routine methods. Compounds 1 and 2 are synthesized under the same hydrothermal conditions except for alternation of the metal cations, however, their eventual structures are different. Compound 1 exhibits a 1D chain, whereas 2 shows a complicated 3D framework. The distinct structural features of the two compounds indicate that metal cations should have great effects on the structures of POM-based organic–inorganic hybrid compounds. The electrochemical properties of 1 and 2 have been also investigated, and the results show that 1 has a good electrocatalytic activity toward reduction of hydrogen peroxide (H₂O₂) molecules ascribed to W-centers.     

Heterometallic chalcogenido clusters containing lanthanides and main group metals: emissive precursors to ternary solid-state compounds

Heterometallic clusters containing lanthanides and the group 12 metals can be isolated as crystalline compounds in high yields. These products [(py)8Ln4M2Se6(SePh)4 (Ln = Er, Yb, Lu; M = Cd, Hg)] adopt a double cubane structure with the covalent M occupying an opposing pair of external metal sites. Both Er/M compounds are strongly emissive materials, with emission lifetimes of 1.41 ms (Er/Cd) and 0.71 ms (Er/Hg) and with the Er/Cd radiative quantum efficiency twice that of the Er/Hg compound. Thermal decomposition of the Er/Cd and Yb/Cd compounds at 650 degrees C give the ternary solid-state materials CdLn2Se4.     

Supramolecular architectures assembled from amphiphilic hybrid polyoxometalates

Polyoxometalate (POM)-based inorganic-organic molecular hybrid clusters have been recently recognized as good candidates to design novel multi-functional materials. Tremendous efforts have been invested in synthesizing many interesting hybrid structures with exceptional chemical and physical properties. Grafting organic ligands to the POM clusters render these functional clusters amphiphilic properties. Here we summarize the current progresses and provide some perspectives, from colloidal chemists' point of view, on the self-assembly of the amphiphilic POM-organic hybrids in solution and at interfaces, as well as the related consequent novel features such as enhanced fluorescent properties.     

Fine-tuned nanostructures assembled from L-lysine-functionalized perylene bisimides

Controllable nanostructures with tunable dimensions were obtained via self-assembly of CBZ-L-lysine-functionalized tetrachloroperylene bisimides (4ClPBI-Lys). Depending on the nature of substitute, solvent polarity, and sample concentration, 4ClPBI-Lys could form nanosphere, nanowire, nanobelt, and nanosheet, which were found to have different degree of molecular ordering. The effects of substitution position with respect to L-lysine on 4ClPBI were also explored in terms of assembly nanostructures. Hydrogen bonding was important to promote formation of long-range ordering. The nanostructures of different assemblies were characterized using SEM, TEM, XRD, UV-vis, and FTIR spectroscopy. For each obtained supramolecular assembly, we also found that the molecular packing motif ultimately determined the corresponding devices' electronic properties.     

Interlocked chiral nanotubes assembled from quintuple helices

Homochiral helical chains were rationally synthesized from C2-symmetric 1,1-binaphthyl-6,6'-bipyridine ligands and linear metal-connecting points, Ni(acac)2. Five such homochiral helices associate in parallel to form nanotubes of 2 x 2 nm in dimensions which further intertwine to form periodically ordered, interlocked nanotubular architectures that possess nanometer-scale open channels and have high affinity for aromatic molecules. Chiral crown ethers have also been successfully incorporated into the walls of these nanotubes, which promises to lead to novel chiral zeolitic materials applicable in enantioselective processes.     

Molecular clips form isostructural dimeric aggregates from benzene to water

We report the synthesis and characterization of eight C-shaped methylene-bridged glycoluril dimers (1-8) bearing hydrogen-bonding amide groups on their aromatic rings. Compounds 1-6 undergo tight dimerization in CDCl3 solution (Ks > 9 x 10(5) M(-1)); binary mixtures of 1-7 form mixtures of homodimers and heterodimers in moderately selective dimerization processes (0.23 < or = Keq < or = 768; 0.253 < or = chiAB < 0.933). The high affinity formation of 1.1-6.6 is due to the commensurate nature of the geometrical constraints imposed by the pi-pi interactions and only two hydrogen bonds. The differential response of the strengths of the pi-pi interactions and H-bonds of 2.2 to changes in solvent polarity--from C6D6 to D2O--results in the formation of a solvent-independent isostructural aggregate that exhibits high affinity dimerization across the full range of solvents.     

Tetrameric molecular bowl assembled from glycoluril building blocks

Glycoluril derivative--whose bulky Ph-C[triple bond]C- substituents prevent formation of H-bonded tapes--undergoes solvent dependent assembly in the crystal; a tetrameric molecular bowl is formed by R(24) H-bonding interactions from CH(2)Cl(2) whereas DMF results in H-bond dimerization followed by oligomerization via C-H...pi interactions.     

Anisotropic two-dimensional sheets assembled from rod-shaped metal complexes

The facile formation of anisotropic two-dimensional sheets with different sizes, ranging from nanometre-scale to micrometre-scale, was achieved by the assembly of rod-shaped palladium complexes.     

Tetrametallic rectangular box complexes assembled from heteroligated macrocycles

The reaction of a heteroligated Rh(I) bimetallic macrocycle with rigid ditopic ligands (1,4-dicyanobenzene, 4-4'-dicyanobiphenyl, or dipyridyl terminated salen ligand 5) results in the formation of tetrametallic rectangular box complexes.     

Framework materials assembled from magnesium carboxylate building units

Four coordination polymers containing magnesium metal nodes and di- or tricarboxylic acid organic connectors have been synthesised and structurally characterised with the aid of single crystal X-ray diffraction. Mg3(bdc)3(DMA)4 (1) and Mg3(bdc)3(EtOH)2 (2) were prepared from the 1 : 1 reaction of 1,4-benzenedicarboxylic acid (H(2)bdc) with Mg(NO3)2.6H2O in dimethylacetamide (DMA) or EtOH respectively. Both 1 and 2 contain tri-metallic magnesium carboxylate units which act as six-coordinate nodes for network construction. These tri-magnesium nodes are joined by the bdc ligands in 1 to give a 2D layered structure with coordinated DMA solvent molecules between the layers, whereas in 2 they stack end-on to form a novel 3D network containing 1D Mg carboxylate chains. Both 1 and 2 are moderately hygroscopic, and powder X-ray diffraction and thermogravimetric analysis studies show them to be interconvertible with Mg(bdc) and the hydrated complex Mg(bdc)(H2O)2 via a series of solid-state reactions. Reaction of magnesium nitrate with 4,4'-biphenyldicarboxylic acid (H(2)bpdc) in DMA gives Mg3(bpdc)3(DMA)4 (3), which in contrast to 2 forms a 'squashed' 3D cubic network as a result of the increased distance between the trinuclear nodes necessitated by the longer bpdc ligands. Reaction of magnesium nitrate with the triangular organic building block 1,3,5-tricarboxylic acid (H(3)btc) in DMA gives crystals of Mg(H(1.5)btc)2/3(btc)1/3(DMA)2.(DMA)1/3 (4). Compound 4 contains mono-metallic metal nodes which assemble with the btc ligands to give 2D 6(3) tessellated layers with Mg-coordinated DMA molecules lying perpendicular to the layers. Some free DMA is also present in 4, sited in small pores between the layers.     

Enzyme responsive supramolecular hydrogels assembled from nonionic peptide amphiphiles

Smart peptide hydrogels are of great interest for their great potential applications. Here, we report a facile approach to prepare a class of enzyme-responsive hydrogels in a scalable manner. These hydrogels self-assemble from a family of nonionic peptide amphiphiles(PAs) synthesized by sequential ring-opening polymerization(ROP) of γ-benzyl-L-glutamate N-carboxyanhydride(BLG-NCA) and L-tyrosine N-carboxyanhydride(Tyr-NCA), followed by subsequent aminolysis. These PA samples can readily form a clear hydrogel with a critical gelation concentration as low as 0.5 wt%. The incorporation of tyrosine residues offers hydrophobicity, hydrogen-bonding interaction and enzyme-responsive properties. The hydrogel-to-nanogel transition is observed under physiological conditions in the presence of horseradish peroxidase(HRP) and hydrogen peroxide(H2 O2). The obtained PA hydrogels are ideal candidates for the new generation of smart scaffolds.     

Synthesis of Coordination Polymers from the Heterometallic Carboxylate Complexes with Chelating N-Donor Ligands

Russian Journal of Coordination Chemistry - New trinuclear Cd–Ln molecular complexes [EuCd2(O2CC6F5)6(NO3)(Bipy)2] (I, Bipy is 2,2'-bipyridine) and [LnCd2(Bzo)6(NO3)(Phen)2] · 4MeCN...     

Manganese Containing Heterometallic Clusters Containing Ligands Derived from Elements of Groups 15 and 16

The area of manganese-containing mixed-metal clusters is reviewed. Discussion is divided into two sections: that containing clusters bridged by ligands derived from elements of Group 15 and those containing ligands derived from the Group 16 elements of the Periodic Table. Emphasis is given to synthetic strategies and those reactivity features which result in Mn-containing new cluster formations. Dedicated to Professor Dr. Dieter Fenske on the occasion of his 65th birthday. Yuri V. Torubaev is on leave from the N.S. Kurnakov Institute of General and Inorganic Chemistry, Leninskii Prospeckt, Moscow, Russia