Duan Chun-ying

Structural dependence of π–π interactions in dithiocarbazato and thiosemicarbazato nickel complexes

Structures and stabilization due to π–π interactions of N2S2 coordinated nickel(II) complexes NiL2 have been investigated by ESI-MS spectrometry and X-ray diffraction methods. For the systems with HL = 4,5-diazafluoren-9-one thiosemicarbazone (HL1), fluoren-9-one thiosemicarbazone (HL2), fluoren-9-one dithiocarbazone (HL3) and 4,5-diazafluoren-9-one dithiocarbazone (HL4), the Ni(II) atom in each complex is coordinated in a distorted square-planar geometry with two aromatic rings positioned on the same side. This cis configuration is stabilized by π–π stacking interactions between the aromatic rings. Detailed structural analyses reveal that whereas the intermolecular π–π stacking interactions connect NiL12 molecules into a one-dimensional screw chain, the intermolecular π–π stacking interactions and the C–H···π interactions link NiL22 molecules into a dimer. The π–π stacking interactions and the C–H···π interactions among the two phenyl rings and two fluorene rings of NiL32 form a closed hydrophobic brick. In NiL12 one of the two phenyl rings interacts with the two 4,5-diazafluorene rings to give an opened hydrophobic cavity; the edge-to-face interactions about another phenyl ring arrange the molecules into a one-dimensional network.

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.

CRYSTAL STRUCTURE AND SPECTROSCOPIC STUDIES OF A NICKEL(II) COMPLEX OF A LIGAND CONTAINING NITROGEN-SULPHUR DONORS

Abstract A bis-ligand neutral Ni(II) complex of a Schiff base ligand derived from S-benzyldithiocarbazate and p-dimethylaminobenzyldehyde was prepared and characterized. Single crystal X-ray diffraction analysis of the nickel(II) chelate established that the Schiff base loses a proton from its tautomeric thiol form and coordinates to Ni(II) via the mercapto sulphur and β-nitrogen atoms. The geometry of the Ni(II) ion is square-planar with two equivalent Ni-N and Ni-S bonds; the two dimethylaminobenzyl rings and the coordinated plane are almost in one plane, forming an electronic delocalization system. When the complex crystallizes, benzene molecules are included in the crystal. However, there is no obvious interaction between the complex molecule and the benzene molecule. Magnetic and spectroscopic data support the square-planar structure found in the structure analysis. The complex crystallizes in the triclinic space group P1 with cell parameters a = 7.839(2), b = 10.528(4), c = 10.832(5) A, α = 100.61(2...

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.

SYNTHESIS, CRYSTAL STRUCTURE AND NONLINEAR OPTICAL PROPERTIES OF THIOSEMICARBAZONE ZINC COMPLEX

Abstract A new zinc bromide complex of a Schiff-base ligand derived from thiosemicarbazide and 4-methoxylphenyldehyde, which shows ca 13 times better SHG efficiency than urea, has been prepared and characterized. Single crystal X-ray diffraction analysis established that the coordination geometry about the zinc atom is tetrahedral with two equivalent Zn-Br and Zn-S bonds. The Schiff-base ligand is coordinated to the Zn(II) via the monodentate mercapto sulfur atom. The polar structure (space group Aba2) is stabilized by hydrogen bonds between the oxygen atom and the amino nitrogen atoms N(l). The complex crystallizes in the orthorhombic space group Aba2 with cell parameters a=11.970(2), b = 21.888(2), c= 9.157(2)A and Z = 4. The structure was solved by direct methods and refined by full-matrix least-squares to R = 0.065 and R w = 0.117 for the 722 observed reflections with I > 2[sgrave](I).

Synthesis and characterization of ferrocene-containing new schiff base complexes. The X-ray crystal structure of (C10H6N2)CNNCHFc

Abstract A series of novel ferrocene-containing Schiff base complexes, (C10H6N2)CNNCRFc, (C10H6N2)CNC6H4NCRFc and (C10H6N2)CNC6H4C6 H4NCRFc (R: H, CH3), have been synthesized using 1,10-phenanthroline and ferrocene as starting materials. The derivatives were characterized by elemental analyses and spectral data (IR, UV, MS and 1H NMR). The single-crystal X-ray structure is presented for (C10H6N2)CNNCHFc (1). The cyclic voltammograms of complex 1 have shown reversible one-electron oxidation and two-step one-electron reduction.

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.