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Metal–organic frameworks [(Fe2L3)·(C4H10O)] 1, [(Fe2L3)·(C5H5N)] (2), [(Fe2L3)·(C6H6)] (3) and [(Fe2L3)·(C4H8O)4] (4), achieved from triple metal helical iron complex Fe2L3, were assembled in the solvents of diethyl ether/DMF, pyridine, benzene and THF, respectively, where H2L is one of the simplest imine-based ligands {[(C6H4)(OH)]CHN–NCH[(OH)(C6H4)]}. Compounds 1, 2, 3 and 4 all crystallize in a centro-symmetric space group, consequently the molecules occur as a racemic mixture of Δ–Δ and Λ–Λ configuration enantiomers, wherein the equivalent fragments are related by the C2 axis. The phenyl rings of the helical units contact the neighbors via π–π (face-to-face) and C–H⋯π interactions to form two-dimensional channeled frameworks in which solvent molecules are absorbed in the channels in each of the structures. Thermogravimetric analyses reveal that the solvent molecules can be evacuated from the pores without loss of the framework periodicity. The crystal lattice is thermally stable up to 350 °C, and diethyl ether can be re-adsorbed by putting the heated material in diethyl ether solvent. It is also interesting to find that upon addition of other solvents such as n-hexane and cyclohexane, thermal gravimetric measurement and elemental microanalysis do not support the absorbance of these guests, indicating that the inclusion can be selectively re-absorbed. All the results indicate that although C–H⋯π interactions have energies that are only in the range of 2–20 kJ mol−1, these interactions are significant enough in combination that the orientation of molecules in the solid can be predicted with a reasonable degree of accuracy.

Three new disilver(I) double helicate complexes [Ag2L2][ClO4]2 (1), [Ag2L2][BF4]2 (2) [Ag2L2][NO3]2 (3) and a polymeric monohelical species [Ag2L′2][BF4]2 (4) have been generated via a self-assembly procedure to establish the effect of a side-chain on the subtle metal–ligand coding. The ligands, L = (C5H4N)C(CH3)N–NC(CH3)(C5H4N) and L′ = (C5H4N)CHN–NCH(C5H4N), were both readily prepared imine-based systems, in which the two bis-bidentate chelating units are separated by a single bond. Complexes 1, 2 and 3 adopt a double helical architecture, in which each silver centre is bound to two pyridylimine units in a distorted tetrahedral coordination geometry. Complex 4 is formed as an infinite monohelical polymer in which each silver centre is coordinated in a distorted tetrahedral geometry by two bidentate binding units from different ligands and the ligands are in turn coordinated to two silver(I) centres. While the two pyridylimine units of the ligand L are able to twist both in its free form and in the double helicates 1, 2 and 3, ligand L′ presents a planar conformation in both the free ligand and its monohelical complex 4. It is speculated that the arrangement of the two pyridylimine units around the N–N bond is essential to encode for a double helicate. Intra- and inter-molecular non-covalent interactions are found to stabilize the polymer 4 and provide opportunities for complexes 1, 2 and 3 to crystallize in different space groups.

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.

The self-assembly and structural characterization of the new ferrocene-containing dicopper(II) double helicate [Cu2L12] (1) and related copper(II) complex [CuL2(CH3CN)][ClO4]2 (2) and silver(I) complexes [AgL2(CH3CN)][BF4] (3) and [AgL2][BF4] (4) have been achieved. These complexes are derived from inexpensive and easy-to-prepare ferrocene-containing bisbidentate Schiff-base ligands H2L1, [(C6H4)(OH)CHNNC(CH3)(C5H4)]2Fe, and L2, [(C5H4N)CHNNC(CH3)(C5H4)]2Fe. The neutral double-helical dicopper(II) complex 1 crystallizes in a polar space group. The two ferrocene-containing ligands strand interwined about each other and around the two tetrahedral copper ions in a double-helical fashion, with the Cu···Cu separation being 9.45 A. The four metal centers are coplanar and form a slightly distorted rhombus with sides of ca. 5.8 A. Reaction of the ligand L2 and copper(II) constructed a mononuclear copper complex, 2. X-ray structural analysis reveals that the copper(II) atom is coordinated in a distorted square pyr...

The structure of complex [PyH][Ni(mnt)2], as determined by X-ray single crystal analysis, consists of pyridinium cations and [Ni(mnt)2]− anions. Crystallographic data for the complex: monoclinic P21/c, a = 16.5430(18) A, b = 6.3847(9) A, c = 17.430(2) A, β = 118.040(7)°, V = 1625.4(3) A3, Z = 4. The [Ni(mnt)2]− anion is not a planar and the CN groups bend away from the S4 plane. The interactions between anions and cations via the formation of bifurcated N–H···N≡C hydrogen bonds give rise to an 1D zigzag chain of alternating cations and anions.

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.

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.

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.

The structure of [NO2Py]2[Ni(mnt)2], as determined by x-ray single crystal analysis, consists of two 1-(4-nitrobenzyl)pyridinium cations and one [Ni(mnt)2]2− anion. The crystallographic data for the complex:monoclinic P21/n, a = 9.913(2) A, b = 11.968(2) A, c = 14.566(3) A, β = 100.36(3)°, V = 1699.9(6) A3, Z = 2. The [Ni(mnt)2]2− anion has a crystallographically imposed center of symmetry and exhibits a relatively planar structure. The cation, [NO2Py]+, adopts a conformation where both the aromatic rings are twisted to the C11-C10-N3 reference plane. The anions (A) and the cations (C) consist of alternating layers (i.e., of type ···C1A1C2A2C1A1C2···) along the c axis of the crystallographic unit cell.

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.

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−.

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.

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.

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.

The binuclear ferrocene derivative, Z-1, 2-dimethyl-1, 2-bis (m-ferrocenylphenyl)e hene (Z-DDFP) has been isolated from the mixture of the coupling reaction of m-ferrocenylacetophenone (m-FAP) by the low-valent titanium salts obtained from zinc/titanium tetrachloride in THF. The single crystal X-ray structure of the complex as benzene solvate has been determined and found to be triclinic with cell constants a=7.748(5), b=10.600(7), c=18.550(4)A, α=97.565(5)°, β=98.551(8)°, γ=90.318(8)° and V=1494.2A3. The structure was refined by [least-squares method for 5151 independent reflections with I>3σ(I) to a final R=0.0363 and Rw=0.0523. The two cyclopentadienyl rings in each ferrocenyl unit are approximately parallel. The two phenyl rings are significantly twisted by 66.80° from each other in the stable configuration. Both the ferrocenyl units on the same side of the C=C double bond are not co-planar with a mean dihedral angle of 96.28°. The structural analysis shows that the chain linking two central iron atoms is about 18A, significantly close to those found in some biological models.