Meng Qing-jin

Self-assembly of a novel mixed-valence tetranuclear molecular square [FeII3FeIIIL2(HL)2]3+ and [M(HL)]44+ squares (M = Ni, Zn and Cd){H2L = bis(2-acetylpyridine) thiocarbazone}

A novel mixed-valence rigid molecular square [FeII3FeIIIL2(HL)2]3+ was constructed via self-assembly using bis(2-acetylpyridine) thiocarbazone (H2L) as both linker and reducing agent. Single crystal structure analysis shows that each cation is located at an inversion center with four iron atoms at the corners of a square with edge length Fe⋯Fe ca. 4.2 A. Magnetic measurement exhibits that there is only one FeIII center in each of the tetranuclear squares. There is no significant difference of the coordinated bonds among the four iron centers, indicating that it is impossible to recognize the FeIII in the four iron centers of a square. Electrochemical measurement and UV–VIS–NIR spectral studies demonstrate the Robin–Day class II behavior of the mixed-valence compound with appreciable iron–iron interaction. New rigid metallocyclic squares [Ni(HL)]44+, [Zn(HL)]44+ and [Cd(HL)]44+ were also assembled and structurally characterized for comparison. ESI-MS spectra reveal that the fragments of tetranuclear molecular squares are stable even in solution.

A supramolecular analog of cyclohexane sustained by aromatic C–H···π interactions between ferrocene moieties: molecular packing of ferrocene-containing thiosemicarbazato metal complexes

Novel supramolecular cyclohexane-like structures, [NiL2] (1) and [ZnL2] (2) (HL=acetylferrocenyl thiosemicarbazone), have been constructed by self-assembly of ferrocene moieties ia aromatic C–H···π interactions. The nickel(II) atom in 1 is coordinated in a distorted square-planar cis configuration with two ferrocene-containing ligands positioned on the same side. One of the ferrocene moieties interacts with symmetry-related species to form a supramolecular arrangement that is topologically equivalent to cyclohexane, but in which edge-to-face C–H···π interactions between ferrocene moieties serve the same structural functions as the C–C bonds in cyclohexane. The zinc(II) atom in 2 is coordinated in a tetrahedral geometry with two equivalent Zn–S and Zn–N bonds. Each ferrocene moiety interacts with symmetry-related species using C–H···π interactions to form a two-dimensional cyclohexane-like network. Powder X-ray diffraction analyses of complexes 1 and 2, together with the palladium(II) complex [PdL2] (3), copper(II) complex [CuL2] (4), and cobalt(II) complex [CoL2] (5) reveal that the supramolecular cyclohexane-like aggregation is robust enough to be exchanged from one network to another. All the results indicate that although C–H···π interactions have energies only in the 2–20 kJ mol−1 range, these interactions are directional enough in combination that the orientation of molecules in the solid can be predicted with a reasonable degree of accuracy.

Synthesis, Characterization and Electrochemical Properties of Cyanide-Bridged Cobalt(III)/Iron(II) Complexes

Abstract Five new cyanide-bridged cobalt(III)/iron(II) complexes have been synthesized. The complexes were characterized by elemental analyses, spectral analyses and electrochemical techniques. The presence of cyanide bridges is evident from the IR and UV-vis spectra by the shift of v(C≡N) and changes in λmax with respect to the mononuclear parent complex Fe(phen)2(CN)2 (phen is 1,10-phenanthroline). The cyclic voltammogram of cyano-bridged cobalt(III)/iron(II) complexes indicates that they all exhibit two pairs of reversible peaks.

A three-dimensional porous metal–organic framework [Fe2L3·(DMF)7·(C4H10O)0.5] constructed from triple-helices {L = bis[2,4-dihydroxybenzaldehyde]hydrazone}

A novel 3-D large porous metal–organic framework was achieved from triple metal helices via π–π stacking interactions between the aromatic groups of the helices.

Spectrophotometric Studies of Cyano-Bridged Complexes of the Type [(Dien) M(II)-μ-NC-Fe(III)(CN)5]−

Abstract Three kinds of new M(II)-μ-NC-iron(III) cyano—bridged complexes [(dien) M-NC-Fe(CN)5]− (M = Ni, Co, Cu) have been synthesized and characterized by elemental analysis, IR, UV—vis spectral analysis. The formation of cyano—bridges is evident from the IR and UV—vis spectra by appearance of v (C≡N) shifts and changes in λmax with respect to the mononuclear parent complex [Fe(CN)6]3−.

Novel ferrocene-based mixed-metal coordination polymers

A novel 2D ferrocene-containing sandwich sheet coordination polymer, consisting of NaZnO inorganic inner and ferrocene-packing outer layers, has been achieved by simply diffusing a solution of Zn(BF4)2 into a solution of 1,1′-ferrocenedicarboxylic acid in the presence of NaOH.

Self-assembled dinuclear molecular box [Ag2L2]2+ and triple helicates [Co2L3]4+, [Ni2L3]4+{L = bis[4-(2-pyridylmethyleneamino)phenyl] ether}

The self-assembly and structural characterization of the new silver(I) molecular box [Ag2L2]2+ and cobalt(II), and nickel(II) molecular helices [Co2L3]4+ and [Ni2L3]4+ have been achieved. These complexes are derived from an inexpensive and easy-to-prepare bis-bidentate Schiff base ligand bis[4-(2-pyridylmethyleneamino)phenyl] ether (L). The cage-like cation [Ag2L2]2+ is located at an inversion center with two tetrahedrally co-ordinated silver(I) atoms and two ether oxygen atoms in the corner of a box. The edge length Ag⋯O is ca. 7.1 A. Each silver(I) center is bound to two pyridylimine units, one from each ligand. One ligand passes above the silver(I)–silver(I) axis, while the other passes beneath, giving a non-helical metallo-cyclophane with Ag⋯Ag separation ca. 12.3 A. Both triple helical [Co2L3]4+ and [Ni2L3]4+ cations contain two metal atoms and three ligands. Each metal center is bound to three pyridylimine units to attain a pseudo-octahedral co-ordination geometry. The ligand wraps in a helical arrangement around the two metal ions. Edge-to-face and face-to-face π–π interactions play important roles in the metal-assisted self-assembling process.

Self-assembled macrocyclic tetranuclear molecular square [Ni(HL)]44+ and molecular rectangle [Cu2Cl2L]2{H2L = bis[phenyl(2-pyridyl)methanone] thiocarbazone}

The conformationally rigid, nickel(II)-based cationic molecular square [Ni(HL)]44+ and copper(II)-based neutral molecular rectangle [Cu2Cl2L]2 were achieved via self-assembly from novel rigid pentadentate N4S ligand bis[phenyl(2-pyridyl)methanone] thiocarbazone (H2L). Crystal structure analyses show that the tetranuclear nickel(II) cation [Ni(HL)]44+ is located at the inversion center with four nickel atoms in the corners of a square with edge length Ni⋯Ni ca. 4.8 A, each metal center being octahedrally coordinated by sulfur atoms, pyridine nitrogen and carbazone nitrogen atoms from two perpendicular HL− ligands. Relative to the square of metal cations the sulfur atoms are midway between the edges of the square, each being connected to two nickel atoms with the angles Ni–S–Ni ca. 163°. The tetranuclear copper(II) complex [Cu2Cl2L]2 is also located in the inversion center with four copper atoms in the corners of a rectangle. Two edges of the rectangle are Cu–S–Cu bridges with edge length Cu⋯Cu of 4.51 A, the other two edges are double Cu–Cl–Cu bridges with Cu⋯Cu distance of 3.41 A. Each metal center is coordinated in a tetragonal-pyramid with the sulfur atom, pyridine nitrogen atom, carbazone nitrogen atom and one chlorine atom comprising the basal plane, whereas the other chlorine atom of the symmetry-related half of the molecule occupies the apical position. The crystal structure of the free ligand is also reported for comparison.

A novel ferrocene–barium sandwich sheet-shaped coordination polymer and its solid-state electrochemistry

A new 2-D ferrocene-containing sandwich sheet coordination polymer, consisting of a BaO inorganic inner polymer and novel ordered ferrocenyl outer layers, has been achieved and structurally characterized; the solid-state redox properties of the barium complex and the related samarium complex have also been investigated.

Synthesis and crystal structure of a triangular nickel(II) complex with the shortest imine-based rigid ligand

A novel triangular complex [Ni(SCN)2L]3 was generated via self-assembly from Ni(SCN)2 and the readily prepared imine-based ligand L, (C5H4N)–CHN–NCH–(C5H4N), by appropriately adjusting the coordination conditions of the metal center.