[en] Infrared spectra were obtained by using a Perkin-Elmer Spectrum X spectrophotometer (Perkin-Elmer, Waltham, MA, USA) between 4000 and 400 cm−1. Thermal and elemental analyses were performed at the analytical laboratory of KRICT, Korea. The free ligand L1 and Zn(L1)(NO_3)_2 were prepared according to the literature procedures, respectively. The microanalytical results and infrared spectra for 1 and 2 agreed well with the structures determined by X-ray diffraction methods. The thermogravimetric analysis (TGA) curve for 1 showed the loss of two lattice water molecules (obs. 6.0%, calcd. 6.0%) between 60 .deg. C and 110 .deg. C

[en] Ketene-forming elimination from 2-X-4-nitrophenyl furylacetates promoted by R₂NH-R₂NH₂⁺ in 70 mol % MeCN(aq) has been studied kinetically. When X = Cl and NO₂, the reactions exhibited second-order kinetics as well as Bronsted β = 0.37-0.54 and |β_lg| = 0.31-0.45. The Bronsted β decreased with a poorer leaving group and |β_lg| increased with a weaker base. The results are consistent with an E2 mechanism. When the leaving group was changed to a poorer one [X= H and OCH₃], the reaction mechanism changed to the competing E2 and E1cb mechanisms. A further change to the E1cb mechanism was realized for the reaction of with i-Pr₂NH/i-Pr₂NH₂⁺ in 70 mol % MeCN-30 mol % D₂O. By comparing the kinetic results in this study with the existing data for ArCH₂C(O)OC₆H₃-2-X-4-NO₂, the effect of the β-aryl group on the ketene-forming elimination was assessed

[en] Upon recrystallization of [Cu(L)](PF_6)_2 from DMF/H_2O, we obtained the DMF coordinated complex as purple plates. The crystals of retain their transparency for several weeks in a refrigerator, but they slowly decompose upon exposure to the atmosphere as evidenced by elemental analysis. The infrared spectrum and microanalysis for clearly support the structure determined by the X-ray diffraction studies as described in the Experimental Section. There have been many examples of copper(II) tetraazamacrocycles, where the axial donors interact with copper(II) ions. However, the complexes reported usually show considerably long Cu-axial donor distances with weak interactions between metal centers and axial donors. Even such weak interactions, it appears that the presence of hydrogen-bonding chelate rings comprised of axial donors, suitable anions and solvents, and secondary amines of the macrocycle is requisite for the stabilization of axial ligands to the central copper(II) ions. In the present work, we describe the preparation and structure of trans-[Cu(L)-(DMF)_2](PF_6)_2, where the complex shows fairly strong copper-axial donor interactions without the support of hydrogen-bonding chelate rings

[en] Two new hexaaza macrocyclic copper(II) complexes were prepared by a template method and structurally characterized. In the solid state, they were self-assembled by intermolecular interactions to form the corresponding supramolecules 1 and 2, respectively. In the structure of 1, the copper(II) macrocycles are bridged by a tp ligand to form a macrocyclic copper(II) dimer. The dimer extends its structure by intermolecular forces such as hydrogen bonds and C-H···π interactions, resulting in the formation of a double stranded 1D supramolecule. In 2, the basic structure is a monomeric copper(II) macrocycle with deprotonated imidazole pendants. An undulated 1D hydrogen bonded array is achieved through hydrogen bonds between imidazole pendants and secondary amines, where the imidazole pendants act as a hydrogen bond acceptor. The 1D hydrogen bonded supramolecular chain is supported by C-H···π interactions between the methyl groups of acetonitrile ligands and imidazole pendants of the copper(II) macrocycles. In both complexes, the introduction of imidazoles to the macrocycle as a pendant plays an important role for the formation of supramolecules, where they act as intermolecular hydrogen bond donors and/or acceptors, C-H···π and π-π interactions

[en] The complex was obtained by reacting the macrocycle and AgNO₃ in MeOH/H₂O. The complex exhibits a 1D supramolecular polymer, where the chain is formed by hydrogen bonds between the two sets of pre-organized N-H groups of the macrocycle, nitrate ions and lattice water molecules. Space-filling and lattice diagrams of illustrating the supramolecular chain by hydrogen bonds are described in Figure 2. The coordination environment around the central Ag(II) ion is a square plane with four Ag-N bonds from the macrocycle. The Ag(II) ion sits on an inversion center. Tetraazamacrocycles and first synthesized by Kang et al., which are two of the 16 possible diastereoisomers of L have long been used for the preparation of many interesting metal complexes. Although the macrocycles and show similar coordination tendencies to metal ions and form corresponding metal complexes, the chemical and structural properties of metal complexes are greatly influenced by the stereochemistry of cyclohexane rings fused on the 14-membered tetraazamacro-cycle

No abstract available

[en] We have prepared and fully characterized the new undulated zinc coordination polymer in which the macrocyclic ligand contains cis-fused cyclohexane rings. The bridging ligand H₂pm in the complex shows the unusual coordination mode to the zinc macrocycle with the involvement of 1,5-COO. rather than 1,4-COO. in coordination. We believe that this unusual structure is caused by the involvement of complex inter- and intramolecular hydrogen bonds between the zinc macrocycle 'connectors' and H₂pm 'linkers', the presence of face-to-face π.π interactions of aromatic rings between the chains as well as the enhanced rigidity and steric hindrance of the macrocycle by the introduction of cis-fused cyclohexane rings and methyl groups on the 14-membered tetraazamacrocycle. Macrocyclic transition metal complexes with polycarbox-ylate ligands have been proved to be good building blocks for the construction of coordination polymers and supramolecular networks. Coordination polymers are generally composed of metal ion 'connectors' and multidentate ligand 'linkers', and the dimensionality of coordination polymers can be tuned by controlling the coordination sites of metal ion 'connectors' for multidentate ligand 'linkers'

[en] The xylyl-bicyclam known as AMD3100 has recently been on clinical trials for the treatment of AIDS. The aspartate residues (Asp 171 and Asp 262) having carboxylate groups of the CXCR4 co-receptor have been understood to participate in the recognition of cyclams. The antiviral activity is greatly enhanced by metal complexation, especially zinc(II) ion, to macrocycles. It is believed that the metal ions of the zinc(II) complexes preferentially recognize the aspartates of the CXCR4 co-receptor by coordination. Therefore, the better knowledge of interactions between zinc(II) macrocycles and carboxylates is crucial for the improved design and development of more effective anti-HIV agents. In this context, we have made an effort to expand upon the examples of carboxylato zinc(II) macrocycles to elucidate the nature of interactions between zinc(II) macrocycles and carboxylates. Herein, we report the synthesis, structure and properties of a new carboxylato zinc(II) complex Zn(L)(apc)₂ (L = 5,16-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0]docosane, apc = 3-amino-2-pyrazinecarboxylate) in which the macrocycle L has a close resemblance to a cyclam

[en] Alpha iron oxide (α-Fe₂O₃) films were grown on catalyst-free silicon substrate using a vertical type metal-organic chemical vapor deposition process. X-ray powder diffraction and field-emission transmission electron microscopy measurements showed that these α-Fe₂O₃ films consisted of bundles of one dimensional (1D) nanorods and the nanorods in these α-Fe₂O₃ films were single crystalline with a well-ordered rhombohedral structure. The nanorods showed a preferred growth orientation in the [104] direction. Magnetic force microscopy image suggests that spin domains were formed in the α-Fe₂O₃ nanorods. Photo-catalytic property of these nanorod films was confirmed through the photo-degradation of Rhodamine B by UV irradiation. These α-Fe₂O₃ film/nanorod materials could be used as building blocks for nanodevice applications