Structural Flexibility of Carboxylate Bridging Exemplified by a Series of μ-Acetato Dizinc Complexes

Simultaneous catalytic oxidation of toluene and CO over Cu-V/Al-Ce catalysts: Physicochemical properties-activity relationship and simultaneous oxidation mechanism

Cu-V/Al-Ce with varying ratios of Al2O3/CeO2 were prepared to study the simultaneous catalytic oxidation of toluene and CO. Experimental results show that Cu-V/20Al-80Ce exhibits optimal simultaneous oxidation activity and good durability. This superior performance is related to Cu-Ce, V-Ce, and Al-Ce interactions, which facilitate the exposure of active centers, the creation of oxygen vacanicies, and efficient electron transfer. The mutual influence between toluene and CO during the simultaneous oxidation is then demonstrated. Toluene hinders CO oxidation through the competitive adsorption and the consumption of reactive oxygen species. CO enhances toluene oxidation, which is comprehensively explained by affecting the competition between the desorption and oxidation of benzaldehyde. Despite the mutual influence between toluene and CO, the pathways of CO and toluene oxidation are mutually independent. Toluene oxidation proceeds sequentially from toluene to benzyl alcohol, benzaldehyde, benzoate, and finally to CO2. Before being completely oxidized to CO2, CO is initially converted to carboxylic acid, hydrogen carbonate, free carbonate ion, bidentate formate, and monodentate carbonate.

Transition metal-substituted Keggin polyoxotungstates enabling covalent attachment to proteinase K upon co-crystallization

POM-protein interaction: a series of 3d metal-substituted Keggin polyoxotungstates was co-crystallized with proteinase K, resulting in covalent bonds to aspartate protein side-chains as a desirable feature of these novel crystallization additives.

Stable Mn2+, Cu2+ and Ln3+ complexes with cyclen-based ligands functionalized with picolinate pendant arms

Cyclen-based ligands containing two picolinate pendant arms form Gd³⁺ complexes remarkably stable and inert with respect to metal ion dissociation.

Gold nanoparticles generated by thermolysis of "all-in-one" gold(I) carboxylate complexes

Consecutive synthesis methodologies for the preparation of the gold(I) carboxylates [(Ph(3)P)AuO(2)CCH(2)(OCH(2)CH(2))(n)OCH(3)] (n = 0-6) (6a-g) are reported, whereby selective mono-alkylation of diols HO(CH(2)CH(2)O)(n)H (n = 0-6), Williamson ether synthesis and metal carboxylate (Ag, Au) formation are the key steps. Single crystal X-ray diffraction studies of 6a (n = 0) and 6b (n = 1) were carried out showing that the P-Au-O unit is essentially linear. These compounds were applied in the formation of gold nanoparticles (NP) by a thermally induced decomposition process and hence the addition of any further stabilizing and reducing reagents, respectively, is not required. The ethylene glycol functionalities, providing multiple donating capabilities, are able to stabilise the encapsulated gold colloids. The dependency of concentration, generation time and ethylene glycol chain lengths on the NP size and size distribution is discussed. Characterisation of the gold colloids was performed by TEM, UV/Vis spectroscopy and electron diffraction studies revealing that Au NP are formed with a size of 3.3 (±0.6) to 6.5 (±0.9) nm in p-xylene with a sharp size distribution. Additionally, a decomposition mechanism determined by TG-MS coupling experiments of the gold(i) precursors is reported showing that 1(st) decarboxylation occurs followed by the cleavage of the Au-PPh(3) bond and finally release of ethylene glycol fragments to give Au-NP and the appropriate organics.

New pyrazole-based ligands with two tripodal binding pockets: potential scaffolds for metallobiosite modeling

The synthesis of a new set of bioinspired dinucleating ligand scaffolds HL1-HL3 based on a bridging pyrazolate with appended chelate arms is reported. The ligands provide two binding compartments akin to the tris(imidazolyl)methane motif, predisposed to act as facially tridentate coordination caps. Potentiometric titrations of HL1 in the presence of Ni2+ and Zn2+ reveal formation of species with a metal:ligand ratio 1:1 in aqueous solution, and UV-vis data for the NiII system suggest that the complex [L12Ni2]2+ with (NiN6) chromophore is formed under appropriate pH conditions. In contrast, trinickel(II) complexes [L2 2Ni3(NO3)4(MeOH)2] (4) and [L2 2Ni3Cl2(MeOH)4]Cl2 (5) could be obtained from MeOH solutions and characterized crystallographically. The anticipated tripodal (N3) binding mode of the ligand is indeed realized for the central NiII ion, but the counteranions or MeOH solvent molecules lead to dissociation of one of the N donor legs for the outer NiII ions with formation of intramolecular H-bonds between a Ni-bound MeOH and the pyrazolate-N. X-ray crystals structures were also obtained for three CuI complexes [L3 2Cu4X2](PF6) 2 with X = PMe3 (6), CNnBu (7), CNC6H3Me2-2,6 (8), where all CuI ions are three-coordinate in a distorted trigonal-planar arrangement. The two inner metals are bound to two imidazole-N from one ligand sidearm and a pyrazolate-N from the other ligand while the outer CuI ions are hosted by the pyrazolate-N and one imidazole-N from the nearby sidearm with the third coordination site filled by the coligand X. Spectroscopic and ESI-MS data suggest that the trinickel complexes stay intact even in coordinating solvents while the Cu (I) complexes in solution are partly dissociated into their bimetallic constituents. The solid state structures observed for the oligonuclear complexes 4- 8 are reminiscent of the coordination motifs previously found for related mononuclear complexes based on tripodal tris(imidazolyl)methane, which corroborates the description of HL1-HL3 as novel binucleating versions of such tris(imidazolyl)methane ligands.