Inorganics2016, 4(2), 13; doi:10.3390/inorganics4020013 (registering DOI) - published 4 May 2016 Show/Hide Abstract
Abstract: An overview of the synthesis, characterization and catalytic applications of polyoxometalates/zeolites composites is given. The solids obtained by direct synthesis of the polyoxometalate in the presence of the zeolite are first described with their applications in catalysis. Those obtained by a direct mixing of the two components are then reviewed. In all cases, special care is taken in the localization of the polyoxometalate, inside the zeolite crystal, in mesopores or at the external surface of the crystals, as deduced from the characterization methods.
Inorganics2016, 4(2), 12; doi:10.3390/inorganics4020012 (registering DOI) - published 4 May 2016 Show/Hide Abstract
Abstract: Some hemoproteins have the structural robustness to withstand extraction of the heme cofactor and replacement with a heme analog. Recent reports have reignited interest and exploration in this field by demonstrating the versatility of these systems. Heme binding proteins can be utilized as protein scaffolds to support heme analogs that can facilitate new reactivity by noncovalent bonding at the heme-binding site utilizing the proximal ligand for support. These substituted hemoproteins have the capability to enhance catalytic reactivity and functionality comparatively to their native forms. This review will focus on progress and recent advances of artificially engineered hemoproteins utilized as a new target for the development of biocatalysts.
Abstract: Many paint, ink and coating formulations contain alkyd-based resins which cure via autoxidation mechanisms. Whilst cobalt-soaps have been used for many decades, there is a continuing and accelerating desire by paint companies to develop alternatives for the cobalt soaps, due to likely classification as carcinogens under the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) legislation. Alternative driers, for example manganese and iron soaps, have been applied for this purpose. However, relatively poor curing capabilities make it necessary to increase the level of metal salts to such a level that often coloring of the paint formulation occurs. More recent developments include the application of manganese and iron complexes with a variety of organic ligands. This review will discuss the chemistry of alkyd resin curing, the applications and reactions of cobalt-soaps as curing agents, and, subsequently, the paint drying aspects and mechanisms of (model) alkyd curing using manganese and iron catalysts.
Abstract: The adsorption of water on solid surfaces is a scientific evergreen which again recently prompted considerable attention in the materials, nano-, and surface science communities, respectively, due to conflicting evidence presented in the most highly regarded scientific journals. This mini review is a brief and personal perspective of the current literature (and our own data) about water adsorption for two examples, namely graphene and silicatene, which are both two-dimensional (2D) crystals. Silicatene, an inorganic companion of graphene, is intriguing as it presents us with the possibility to synthesize a 2D analog to zeolites by doping this crystalline silicon film. The wettability by water and whether or not support effects of epitaxial 2D crystals are present is of concern. Regarding applications: some 2D crystals appear promising for the hydrogen evolution reaction, i.e., hydrogen generation from water; a functionalization of graphene (by oxygen/water) to graphene oxide may be interesting for metal-free catalysis; the latest highlight in this field appears to be “icephobicity”, an application related to the hydrophobicity of surfaces.
Abstract: Silica monoliths featuring either mesopores or flow-through macropores and mesopores in their skeleton are prepared by combining spinodal phase separation and sol-gel condensation. The macroporous network is first generated by phase separation in acidic medium in the presence of polyethyleneoxides while mesoporosity is engineered in a second step in alkaline medium, possibly in the presence of alkylammonium cations as surfactants. The mesoporous monoliths, also referred as aerogels, are obtained in the presence of alkylpolyethylene oxides in acidic medium without the use of supercritical drying. The impact of the experimental conditions on pore architecture of the monoliths regarding the shape, the ordering, the size and the connectivity of the mesopores is comprehensively discussed based on a critical appraisal of the different models used for textural analysis.
Abstract: In the context of our systematic investigations of penta- and hexacoordinate silicon compounds, which included dianionic tri- (O,N,O′; O,N,N′) and tetradentate (O,N,N,O; O,N,N′,O′) chelators, we have now explored silicon coordination chemistry with a dianionic tetradentate (N,N′,N′,N) chelator. The ligand [o-phenylene-bis(pyrrole-2-carbaldimine), H2L] was obtained by condensation of o-phenylenediamine and pyrrole-2-carbaldehyde and subsequently silylated with chlorotrimethylsilane/triethylamine. Transsilylation of this ligand precursor (Me3Si)2L with chlorosilanes SiCl4, PhSiCl3, Ph2SiCl2, (Anis)2SiCl2 and (4-Me2N-C6H4)PhSiCl2 afforded the hexacoordinate Si complexes LSiCl2, LSiPhCl, LSiPh2, LSi(Anis)2 and LSiPh(4-Me2N-C6H4), respectively (Anis = anisyl = 4-methoxyphenyl). 29Si NMR spectroscopy and, for LSiPh2, LSi(Anis)2 and LSiPh(4-Me2N-C6H4), single-crystal X-ray diffraction confirm hexacoordination of the Si atoms. The molecular structures of LSiCl2 and LSiPhCl were elucidated by computational methods. Despite the two different N donor sites (pyrrole N, X-type donor; imine N, L-type donor), charge delocalization within the ligand backbone results in compounds with four similar Si–N bonds. Charge distribution within the whole molecules was analyzed by calculating the Natural Charges (NCs). Although these five compounds carry electronically different monodentate substituents, their constituents reveal rather narrow ranges of their charges (Si atoms: +2.10–+2.22; monodentate substituents: −0.54–−0.56; L2−: −1.02–−1.11).