Dan-Feng Wang

pH-Dependent Ag(I) coordination architectures constructed from 4-cyanopyridine and phthalic acid: from discrete structure to 2D sheet

Four mixed-ligand Ag(I) coordination complexes (CCs), namely, [Ag(cnpy)2(Hpta)] (1), [Ag2(cnpy)2(Hpta)2] (2), [Ag4(cnpy)2(pta)2(H2O)]n (3) and [Ag2(inta)2(pta)·3H2O]n (4), (cnpy = 4–cyanopyridine, H2pta = phthalic acid, inta = isonicotinamide) have been synthesized through a one-pot ultrasonic reaction of silver(I) oxide, cnpy and H2pta under different pH values and structurally characterized. Complexes 1 and 2 formed at lower pH values (5.0 for 1 and 6.9 for 2) exhibit zero-dimensional (0D) mononuclear and tetranuclear motifs, respectively. Reaction at pH = 8.8 leads to a two-dimensional (2D) structure of 3 in which completely deprotonated H2pta shows two kinds of coordination modes: μ5-η1:η1:η1:η3 and μ6-η1:η1:η1:η3. A further increase of the pH value to 9.4 results in the in situhydrolysis of cnpy and produces complex 4 as a one-dimensional (1D) chain structure. Of particular interest, a well-resolved chair-like centrosymmetric hexamer water cluster, (H2O)6, which is stabilized by 1D chains through six dangling hydrogen bonds, exists in 4. Comparing the experimental results, it is comprehensible that the pH value plays a crucial role in the formation of the resulting structures. Additionally, results about IR spectra, thermogravimetric curves and photoluminescence spectra were discussed.

Syntheses, structures and fluorescence of two coordination complexes of Zn(II) and 1,3-bis(2-methylimidazolyl)propane: solvent effect

Two Zn(II) coordination complexes, formulated as [Zn2(bmip)(tpa)2·2DMF]n (1) and [Zn(bmip)(tpa)·3H2O]n (2) (bmip = 1,3-bis(2-methylimidazolyl)propane, H2tpa = terephthalic acid, DMF = N,N-dimethylformamide) have been prepared by ultrasonic reactions of the flexible ligand bmip and aromatic dicarboxylic acid H2tpa with Zn(II) ions in various solvent systems. Both of these complexes have been characterized by elemental analyses, IR spectra, and single-crystal X-ray diffraction. As controlled by solvent systems, complex 1 is a 2-fold interpenetrating 3D framework with α-Po network topology, while, complex 2 reveals a 3-fold interpenetrating 3D framework with dia topology. Furthermore, the photoluminescence at room temperature and thermogravimetric properties of the complexes 1 and 2 were also investigated in the solid state.

Synthesis, characterization, crystal structures and thermal and photoluminescence studies of dimethylpyrazine-carboxylate mixed ligand silver(I) coordination polymers with various multinuclear silver units

Seven new silver(I) coordination compounds based on dimethylpyrazine (dmpyz), [Ag4(2,5-dmpyz)(ndc)2]n (1), [Ag2(2,5-dmpyz)(pma)0.5]n (2), [Ag4(2,3-dmpyz)2(mpa)2]n (3), [Ag2(2,3-dmpyz)(npa)]n (4), [Ag(2,3-dmpyz)0.5(opa)0.5]n (5), [Ag6(2,3-dmpyz)3(mpa)3]n (6) and [Ag6(2,3-dmpyz)2(tma)2·5H2O]n (7), have been synthesized and have been characterized by elemental analyses, IR spectra and single-crystal X-ray diffraction. In compound 1, two types of Ag4 units are linked by organic ligands to form a three-dimensional supramolecular framework. Compound 2 also shows a 3D network structure based on [Ag4O2] six-membered rings. Compounds 3 and 6 are both 2D 44-sql nets, in which Ag4 units and Ag6 units are observed, respectively. In compound 4, the npa ligand adopts a μ5-η1:η1:η1:η2 mode to link zigzag Ag4 subunits (SBUs), giving a 2D network. Compound 5 shows a 1D infinite silver chain clamped by the opa ligands. In 7, six coordinated Ag(I) ions propagate to an infinite 1D silver strap and the 2,3-dmpyz and tma ligands link the silver strap into a 3D framework. The high structural diversity of the compounds and the Ag units is highly dependent on the solvent and the coordination mode of the carboxylate. The thermal stabilities and photoluminescence behaviours of the compounds were also discussed.

A Zn-oxalate helix linked by a water helix: spontaneous chiral resolution of a Zn helical coordination polymer

Two enantiomers of a helical coordination polymer [Zn(ox)(H2O)2]·2H2O (1P and 1M) have been obtained from spontaneous chiral resolution. Structural analysis reveals that 1P comprises a right-handed helix with Zn in the Δ-configuration, while 1M comprises a left-handed helix with Zn in the Λ-configuration. Homochiral packing of the Zn-oxalate helix is accomplished with the aid of the water helix comprising coordinated and guest water. FTIR, vibrational circular dichroism (VCD), PXRD and thermogravimetric analysis (TGA) have also been performed for the compound.