Surfactant-concentration-dependent shape evolution of Au-Pd alloy nanocrystals from rhombic dodecahedron to trisoctahedron and hexoctahedron.

The surface structure-controlled synthesis of noble metal nanocrystals (NCs) bounded by high-index facets has become a hot research topic due to their potential to significantly improve catalytic performance. This study reports the preparation of monodisperse Au-Pd alloy NCs with systematic shape evolution from rhombic dodecahedral (RD) to trisoctahedral (TOH), and hexoctahedral (HOH) structures by varying the concentration of surfactant in the surfactant-mediated synthesis. The as-prepared three kinds of alloy NCs possess almost the same size and composition as each other. It is suggested that the surfactant containing long-chain octadecyltrimethyl ammonium (OTA(+)) ions plays a key role in the formation of high index facets, and the crystal growth kinetics may also have an effect on the formation of different nanocrystal morphologies. In addition, the catalytic activities of these NCs are evaluated by structure-sensitive reactions, including ethanol electro-oxidation and the catalytic reduction of 4-nitrophenol (4-NPh). These three types of Au-Pd alloy NCs exhibit different catalytic selectivities towards these two reactions. The catalytic activities toward electro-oxidation of ethanol are in the order of HOH > RD > TOH, which follows the order of their corresponding surface energies. However, the activities toward catalytic reduction of 4-NPh are in the order of RD > TOH > HOH, which should be related to the local structure of the surfaces.

Thermally induced and photoinduced valence tautomerism in a two-dimensional coordination polymer.

Herein reported is the first two-dimensional coordination polymer capable of undergoing thermally induced and photoinduced valence tautomeric transitions.

Two novel silver(I) coordination polymers: poly[(mu2-2-aminopyrimidine-kappa2N1:N3)bis(mu3-thiocyanato-kappa3S:S:S)disilver(I)] and poly[(2-amino-4,6-dimethylpyrimidine-kappaN)(mu3-thiocyanato-kappa3N:S:S)silver(I)].

2-Aminopyrimidine (L1) and 2-amino-4,6-dimethylpyrimidine (L2) have been used to create the two novel title complexes, [Ag2(NCS)2(C4H5N3)]n, (I), and [Ag(NCS)(C6H9N3)]n, (II). The structures of complexes (I) and (II) are mainly directed by the steric properties of the ligands. In (I), the L1 ligand is bisected by a twofold rotation axis running through the amine N atom and opposite C atoms of the pyrimidine ring. The thiocyanate anion adopts the rare mu3-kappa3S coordination mode to link three tetrahedrally coordinated Ag(I) ions into a two-dimensional honeycomb-like 6(3) net. The L1 ligands further extend the two-dimensional sheet to form a three-dimensional framework by bridging Ag(I) ions in adjacent layers. In (II), with three formula units in the asymmetric unit, the L2 ligand bonds to a single Ag(I) ion in a monodentate fashion, while the thiocyanate anions adopt a mu3-kappa1N,kappa2S coordination mode to link the AgL2 subunits to form two-dimensional sheets. These layers are linked by N-H...N hydrogen bonds between the noncoordinated amino H atoms and both thiocyanate and pyrimidine N atoms.

catena-Poly[[[(iminodiacetato-kappaO)silver(I)]-mu3-2-aminopyrimidine-kappa3N1:N2:N3] monohydrate]: a one-dimensional silver(I) coordination polymer with mixed ligands.

The title compound, {[Ag(C4H6NO4)(C4H5N3)].H2O}n, was synthesized by the reaction of silver(I) nitrate with 2-aminopyrimidine and iminodiacetic acid. X-ray analysis reveals that the crystal structure contains a one-dimensional ladder-like Ag(I) coordination polymer and that N-H...O and O-H...O hydrogen bonding results in a three-dimensional network. The Ag(I) centre is four-coordinated by three N atoms from three different 2-aminopyrimidine ligands and one O atom from one iminodiacetate ligand. Comparison of the structural features with previous findings suggests that the existence of a second ligand plays an important role in the construction of such polymer frameworks.

Poly[bis(mu2-2-aminopyrazine-kappa2N1:N4)(mu2-nitrato-kappa2O:O)(nitrato-kappa2O,O')disilver(I)]: an achiral two-dimensional coordination polymer forming chiral crystals.

The solution reaction of AgNO(3) and 2-aminopyrazine (apyz) in a 1:1 ratio gives rise to the title compound, [Ag(2)(NO(3))(2)(C(4)H(5)N(3))(2)](n), (I), which possesses a chiral crystal structure. In (I), both of the crystallographically independent Ag(I) cations are coordinated in tetrahedral geometries by two N atoms from two apyz ligands and two O atoms from nitrate anions; however, the Ag(I) centers show two different coordination environments in which one is coordinated by two O atoms from two different symmetry-related nitrate anions and the second is coordinated by two O atoms from a single nitrate anion. The crystal structure consists of one-dimensional Ag(I)-apyz chains, which are further extended by mu(2)-kappa(2)O:O nitrate anions into a two-dimensional (4,4) sheet. N-H...O and C(apyz)-H...O hydrogen bonds connect neighboring sheets to form a three-dimensional supramolecular framework.

Stepwise assembly of homochiral coordination polymers based on the precursor of an enantiopure Yb3Mn6 cluster.

Two homochiral coordination polymers, namely, [Yb(III)(3)Mn(III)(6)(L)(6)(µ(2)-OMe)(6)(isonicotinate)(2)(HOMe)(2)][Yb(III)(3)Mn(III)(6)(L)(6)(µ(2)-OMe)(6)(isonicotinate)(2)(HOMe)(4)](NO(3))(2)·6MeOH·12H(2)O (5) (H(3)L = (S,E)-4-(2-hydroxybenzylideneamino)-2-hydroxybutanoic acid) and [Yb(III)(3)Mn(III)(6)Na(L)(6)(µ(2)-OMe)(6)(OOCH)(3)]I·17H(2)O (6), have been constructed by utilizing a stable enantiopure [Yb(III)(3)Mn(III)(6)(L)(6)(µ(2)-OMe)(6)](3+) (Yb(3)Mn(6)) cluster as a precursor.