The mechanism for the oxidation of 3'-dGMP by [PtCl(4)(dach)] (dach = diaminocyclohexane) in the presence of [PtCl(2)(dach)] has been investigated using density functional theory. We find that the initial complexation, i.e., the formation of [PtCl(3)(dach)(3'-dGMP)], is greatly assisted by the reaction of the encounter pair [PtCl(2)(dach)···3'-dGMP] with [PtCl(4)(dach)], leading to migration of an axial chlorine ligand from platinum(IV) to platinum(II). A dinuclear platinum(II)/platinum(IV) intermediate could not be found, but the reaction is predicted to pass through a platinum(III)/platinum(III) transition structure. A cyclization process, i.e., C8-O bond formation, from [PtCl(3)(dach)(3'-dGMP)] occurs through an intriguing phosphate-water-assisted deprotonation reaction, analogous to the opposite of a proton shuttle mechanism. Followed by this, the guanine moiety is oxidized via dissociation of the Pt(IV)-Cl(ax) bond, and the cyclic ether product is finally formed after deprotonation. We have provided rationalizations, including molecular orbital explanations, for the key steps in the process. Our results help to explain the effect of [PtCl(4)(dach)] on the complexation step and the effect of a strong hydroxide base on the cyclization reaction. The overall reaction cycle is intricate and involves autocatalysis by a platinum(II) species.

Functionalization of mesoporous SBA-15 frameworks by transition metal oxides offers a flexible route to fabricate new heterogeneous catalysts. Here, an inorganic-organic hybrid nanoporous catalyst H 5 PW 10 V 2 O 40 @VO x /SBA-15-NH 2 , was prepared and utilized as an efficient, ecofriendly, and recyclable catalyst for the one-pot, multi-component synthesis of 3-substituted indoles by indole substitution with aldehydes and malononitrile under solvent-free conditions. Catalysts were prepared by the non-covalent attachment of H 5 PW 10 V 2 O 40 to a 3 wt%VO x /SBA-15 nanoporous support through a 3-(triethoxysilyl)propylamine linker. VO x /SBA-15 was prepared by a one-pot hydrothermal synthesis from TEOS and vanadium(V) oxytri-tert-butoxide [VO(O-t Bu) 3 ]. The resulting H 5 PW 10 V 2 O 40 @VO x /SBA-15-NH 2 material was characterized by bulk and surface analysis including N 2 porosimetry, FE-SEM, XRD, XPS, FT-IR, TGA-DTA, UV-Vis and ICP-OES, evidencing retention of the heteropolyacid Keggin structure. H 5 PW 10 V 2 O 40 @VO x /SBA-15-NH 2 exhibits high activity and excellent yields (70-95 %) of 3substituted indoles under mild conditions, with negligible deactivation.

SBA‐15‐PS/phthalhydrazide (PHD) is presented as a new heterogeneous inorganic–organic nanohybrid photocatalyst with high stability, superior recyclability and remarkable performance in the degradation of methyl orange (MO). Distinctive parameters, including photocatalyst and dye concentrations, pH and degradation time, were assessed for MO degradation catalysed by SBA‐15‐PS/PHD. This new heterogeneous nanocatalyst was characterized using Fourier transform infrared and UV–visible spectroscopies, thermogravimetric analysis, scanning and transmission electron microscopies and elemental analysis. Photodegradation of MO of up to 92% under the optimum conditions (photocatalyst = 0.015 g, [MO] = 4 ppm, pH = 2) was accomplished in 25 min using SBA‐15‐PS/PHD. A preliminary kinetic investigation was performed, and pseudo‐first‐order kinetics with a high rate constant (0.068 min−1) was found for MO degradation. Additional results showed that the photodegradation of MO was increased in the presence of hole scavengers. Therefore a photoreduction mechanism for MO degradation is proposed.

The mechanism for the polymerization of ethylene via a mononuclear aluminum catalyst has been shown previously to lead to inconsistent results. We propose here for the first time a plausible mechanism involving a dinuclear aluminum species which overcomes the problems of the mononuclear catalyst. With the aid of computational quantum chemistry, we have shown that the dinuclear pathway has a much lower activation energy than the mononuclear pathway, a result which can be explained in terms of a greater orbital overlap being maintained in the dinuclear transition structure. We show that the generation of one growing polymer chain is more likely than that of two or three growing polymer chains. Importantly we find that the propagation step is more favorable than termination, which is in contrast to the findings with the mononuclear catalyst.

The cleavage of one N-O bond in NO2 by two equivalents of Mo(NRAr)3 has been shown to occur to form molybdenum oxide and nitrosyl complexes. The mechanism and electronic rearrangement of this reaction was investigated using density functional theory, using both a model Mo(NH2)3 system and the full [N((t)Bu)(3,5-dimethylphenyl)] experimental ligand. For the model ligand, several possible modes of coordination for the resulting complex were observed, along with isomerisation and bond breaking pathways. The lowest barrier for direct bond cleavage was found to be via the singlet η(2)-N,O complex (7 kJ mol(-1)). Formation of a bimetallic species was also possible, giving an overall decrease in energy and a lower barrier for reaction (3 kJ mol(-1)). Results for the full ligand showed similar trends in energies for both isomerisation between the different isomers, and for the mononuclear bond cleavage. The lowest calculated barrier for cleavage was only 21 kJ mol(-1)via the triplet η(1)-O isomer, with a strong thermodynamic driving force to the final products of the doublet metal oxide and a molecule of NO. Formation of the full ligand dinuclear complex was not accompanied by an equivalent decrease in energy seen with the model ligand. Direct bond cleavage via an η(1)-O complex is thus the likely mechanism for the experimental reaction that occurs at ambient temperature and pressure. Unlike the other known reactions between MoL3 complexes and small molecules, the second equivalent of the metal does not appear to be necessary, but instead irreversibly binds to the released nitric oxide.