In A Zinc Research Articles

Polymorph driven diversification of photosalient responses in a zinc(II) coordination complex.

A novel crystallographic form of a Zn(II) coordination complex [Zn(4-ohbz)2(4-nvp)2] (1-Form-III) (H4-ohbz = 4-hydroxybenzoic acid and 4-nvp = (E)-4-(1-naphthylvinyl)pyridine), undergoes a solid-state photochemical [2+2] cycloaddition reaction accompanied by a moderate photosalient effect, whereby single-crystals show cracking and splitting. This UV-induced cycloaddition accompanies a single-crystal to single-crystal transformation, allowing for continuous monitoring of the unit cell parameters. The new polymorph represents an intermediate form of the two previously reported crystallographic forms of [Zn(4-ohbz)2(4-nvp)2], and provides novel insight into moderating the magnitude of photosalient responses across polymorphic materials.

Curved crystal morphology, photoreactivity and photosalient behaviour of mononuclear Zn(II) complexes.

A dramatic effect of crystal morphology, photoreactivity and photosalient property is observed in a zinc(II) complex due to solvent effects and fluorine substitution at the backbone of the ligand. Of the two crystal forms with a 3-fluoro derivative, one yielded a curved morphology of single crystals and the second form shows photoreactivity in the solid state, whereas crystals of the 2-fluoro derivative pop during the [2 + 2] photocycloaddition reaction. This is the first report documenting curved single crystals of metal complexes obtained naturally during crystallization, although such bent crystals have been observed in extended solids naturally, or bent by mechanical force or by UV irradiation.

A detailed first principle study on the structural, elastic, and electronic properties of indium arsenide (InAs) under induced pressure

An ab initio calculation of the structural, elastic, and electronic properties of indium arsenide (InAs) under induced pressure is investigated using density functional theory with modified Becke–Johnson potential within the generalised gradient approximation of the Perdew–Burke–Ernzerhof scheme. The lattice parameters are found to be in good agreement with experimental and other theoretical data. The pressure-induced structural phase transition of InAs zinc blende to rock salt structure is found to occur at 4.7 GPa pressure with a 17.2% of volume collapse. The elastic properties of both the zinc blende and rock salt structures at different pressures are studied. The electronic band structures at different pressures for both the structures are investigated using the total and partial density of states. The energy band gap of the InAs zinc blende phase is increased with increasing pressure while in rock salt the phase the conduction band crosses towards the valence band and thus shows metallic behaviour.

Unusual self-assembled 1D tape of tetramers and water–nitrate clusters trapped in a zinc(II) complex: Synthesis, characterization, luminescence and catalytic properties

Unusual tetramers and water–nitrate clusters have been observed in a mononuclear zinc(II) complex of [Zn(4-cpa)(phen)2(H2O)]·(H2O)·(NO3)] (1), (4-Hcpa=4-chlorophenoxyacetic acid, phen=1,10-phenanthroline), which was synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction, UV–vis absorption spectra and single-crystal X-ray diffraction. The crystal structure analysis of 1, reveals that the nitrate anions, water molecules and carboxylate oxygen atoms (O3) pack to form a one-dimensional infinite tape parallel to the c-axis. The uncoordinated carboxylate oxygen atoms (O3) of 4-cpa ligands, water molecules and nitrate anions interact via hydrogen bonds and extend 1 into a water–anion-cation tape, which are finally connected into a 3D supramolecular structure via π⋯π stacking interactions. Excitation (λex=310nm) and luminescence data observed at room temperature show that 1 emits bright blue fluorescence. Moreover, 1 has a remarkable activity for degradation of methyl orange in a photo-assisted Fenton-like process.

Switching from Bonding to Nonbonding: Temperature-Dependent Metal Coordination in a Zinc(II) Sulfadiazine Complex

The metal coordination in the mononuclear complex diamminebis(sulfadiazine)zinc shows a unique temperature dependence: High-resolution diffraction data prove that the coordination is almost tetrahedral at 100 K, whereas a fifth longer interaction becomes relevant at 200 K. The change in the geometry is fully reversible and is also reflected in the charge density of the compound.

Coexistence of two conformational isomeric chains in a zinc(II) phosphonate induced by π···π stacking interactions

Hydrothermal reaction of zinc acetate with diethyl [(phenylsulfonyl)methyl]phosphonate as well as 1,10-phenanthroline (phen) afforded a novel zinc(II) phosphonate with the formula of [Zn4(PhSO2CH2PO3)4(phen)2(H2O)2]·2H2O. Such compound features two conformational isomeric 1D chains which are regulated by two different π···π stacking interactions. In addition, it exhibits broad blue fluorescent emission band at 387 nm.

Epoxide ring opening in a zinc(II) complex in water without any Lewis acid catalyst: Formation of only one diastereomer out of 23

The epoxide ring in 5,6-dihydro-5,6-epoxy-1,10-phenanthroline (L) opens up in its reaction with 4-methylaniline and 4-methoxyaniline in water in equimolar proportion at room temperature without any Lewis acid catalyst to give a monohydrate of 6-(4-methyl-phenylamino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L′·H2O) and 6-(4-methoxyphenyl-amino)-5,6-dihydro-1,10-phenanthrolin-5-ol (L″) respectively. Reaction time decreases from 72 to 14h in boiling water. But the yields become less. Reaction of L with Zn(ClO4)2·6H2O in methanol in 3:1 molar ratio at room temperature affords white [ZnL3](ClO4)2·H2O. The X-ray crystal structure of the acetonitrile solvate [ZnL3](ClO4)2·MeCN has been determined which shows that the metal has a distorted octahedral N6 coordination sphere. [ZnL3](ClO4)2·2H2O reacts with 4-methylaniline and 4-methoxyaniline in boiling water in 1:3 molar proportion in the absence of any Lewis acid catalyst to produce [ZnL′3](ClO4)2·4H2O and [ZnL″3](ClO4)2·H2O, respectively in 1–4h time in somewhat low yield. In the 1H NMR spectra of [ZnL′3](ClO4)2·4H2O and [ZnL″3](ClO4)2·H2O, only one sharp methyl signal is observed implicating that only one diastereomer out of the 23 possibilities is formed. The same diastereomers are obtained when L′·H2O and L″ are reacted directly with Zn(ClO4)2·6H2O in tetrahydrofuran at room temperature in very good yields. Reactions of L′·H2O and L″ with Ru(phen)2Cl2·2H2O (phen=1,10-phenanthroline) in equimolar proportion in methanol–water mixture under refluxing condition lead to the isolation of two diastereomers of [Ru(phen)2L′](ClO4)2·2H2O and [Ru(phen)2L″](ClO4)2·2H2O.

Ancillary ligand-mediated syntheses and fluorescence properties of zinc(ii) complexes based on flexible benzene dicarboxylic acid

This work presents a well-defined synthetic system exemplifying the effect of N-donor ancillary ligands on the formation of complex architectures in a zinc(II)-H2hmph-H2O system by the mild hydrothermal route (H2hmph = homophthalic acid). The single-crystal X-ray diffractions reveal that structure variation of isolated three complexes spans the range of dimensionalities from 2D lamella [Zn(hmph)(bpe)]n (1), 2D thick-layer [Zn(hmph)(bpp)]n (2) to 3D microporous framework {[Zn2(hmph)(trz)2]·H2O}n (3), showing the marked sensitivity of the structures to the flexibility of varied N-donor ancillary ligands (bpe = 1,2-di(4-pyridyl)ethylene, bpp = 1,3-di(4-pyridyl)propane, and Htrz = 1,2,4-triazole). The structures of three complexes can be considered as the assembly of various chain-like structure motifs. The 2D lamella structure of 1 features hmph-bridged binuclear zinc(II) chains joined by less flexible trans-bpe ligands, whereas the 2D thick-layer of 2 manifests hmph-bridged mononuclear zinc(II) chains cross-linked further by flexible bpp legands along two different directions. The alternate opposite chiral helixes, featuring rigid trz-bridged mononuclear zinc(II), and additional binuclear zinc(II) units are cohered together by hmph linkers yielding a 3D microporous coordination network of 3 with new framework topology. It is shown that the structures, packing densities, and thermal stabilities of all these complexes are markedly sensitive to the molecule size, conformation, and flexibility of varied N-donor ancillary ligands. Furthermore, fluorescence properties of complexes 1–3 are also investigated.

Flavin Core as Electron Acceptor Component in a Zinc(II)-Phthalocyanine-Based Dyad

A zinc(ii)-phthalocyanine-flavin dyad has been synthesized by Heck-type cross-coupling between a flavin that bears a p-iodophenyl group and a phthalocyanine functionalized with a vinyl moiety. Electrochemical experiments reveal that no significant interaction occurs at the ground state between the two electroactive subunits. However, the occurrence of a photoinduced electron transfer in this donor–acceptor conjugate is observed in transient absorption experiments. Charge-separation (i.e., 4.0 × 1011 s–1) and charge-recombination dynamics in benzonitrile (2.2 × 1010 s–1) reveal a remarkable stabilization of the radical ion pair in this solvent.

Metal ion recognition. Interaction of a series of successively N-benzylated derivatives of 1,4,8,11-tetraazacyclotetradecane (cyclam) with selected transition and post-transition metal ions

The interaction of a series of N-benzylated cyclam ligand derivatives incorporating from one to four N-benzyl groups with cobalt(II), zinc(II), cadmium(II), lead(II) and silver(I) nitrates is reported; the results are compared with those obtained in a prior study involving the formation of the corresponding complexes of nickel(II) and copper(II) with this ligand series. The isolation of a selection of 1 ∶ 1 (metal ∶ ligand) complexes has been carried out and X-ray diffraction structures of five such products have been determined. In each complex the metal ion is coordinated to the N4-donor set of the cyclam ring with the latter adopting either a trans-I or a trans-V configuration; monodentate or bidentate nitrato ligands complete the respective coordination spheres. Coordination numbers range from five in a zinc(II) complex, through six in two cadmium(II) complexes, to eight in two lead(II) complexes. Competitive bulk membrane transport experiments (water/chloroform/water) have been carried out in which each of the five benzylated ligands were in turn employed as the ionophore in the chloroform phase. The respective aqueous source phases (buffered at pH 4.9) contained an equimolar mixture of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) nitrates. The aqueous receiving phase was buffered at pH 3.0. Under these conditions, high selectivity for copper(II) was observed for each of the ionophores incorporating one or two N-benzyl groups whereas no transport for any of the seven metals present in the source phase was observed for the tribenzylated derivative. In marked contrast to the above behaviour, the tetra-N-benzyl derivative yielded sole transport selectivity for silver(I) under similar conditions. 1H NMR and 13C NMR titration experiments in CD3CN–CDCl3 confirmed the 1 ∶ 1 stoichiometry of the silver(I) tetra-N-benzylcyclam complex in this solvent mixture.

Molecular Rods in a Zinc(II) Porphyrin/Cyclohexane Physical Gel: Neutron and X-ray Scattering Characterizations

Aggregation of some low-molecular weight compounds in organic liquids is known to result in the formation of rod-shaped colloidal particles.1 Beyond the overlap concentration of the aggregates, the systems usually exhibit remarkable viscoelastic features which account for their description as gel-like materials. In particular, their typical consistency results from the development of a three-dimensional network made of interconnected colloidal aggregates. The sensitivity of the aggregation process to parameters such as temperature, concentration, and impurities, the fragility of the resulting network, and its thermal reversibility characterize such systems whose structural study raises specific problems.1 By contrast to the commonly used electron microscopy technique, the small-angle scattering techniques enable a nondestructive investigation of these materials swollen by their solvents. Furthermore, comparative X-ray and neutron studies can provide complementary information concerning the internal structure of the aggregates, such as their cross-sectional heterogeneity or contrast profile.2