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The present theoretical study was carried out to investigate the NO reduction by CO over a Ti-porphyrin catalyst. Thus, density functional theory with and without the van der Waals correction was employed. The calculated adsorption energies show that the Ti-porphyrin is active in bending the NO and CO molecules. So, we proposed two reaction mechanisms for the NO reduction by CO on Ti-porphyrin. The calculated activation energies show that both mechanisms are plausible and feasible at room temperature. The Ti-porphyrin shows a good catalytic activity to NO reduction by CO compared to conventional Rh cluster catalyst. These results indicate that the Ti-porphyrin is a promising candidate for reducing NO and CO gases from our environment. [ABSTRACT FROM AUTHOR]

Four new zinc(II) complexes of the type [ZnCl2(n-Bu3PE)2] (E=O (1), S (2), Se (3), or Te (4)) have been synthesized from zinc(II) chloride and the ligands n-Bu3PE giving yields of 56–88%. The adducts were characterized by multinuclear (31P, 13C, and 77Se) NMR, conductivity, IR spectroscopy and by X-ray analyses. Zinc complexes 1–4 are compriseS of two ligands coordinated to the metal center in a distorted tetrahedral arrangement. The P=E bond lengths of 1.497(7) (E=O), 2.000(4) (E=S), and 2.178(2) Å (E=Se) in these complexes are slightly elongated compared to those in the free ligand. In addition, a DFT/B3LYP theoretical study on the geometry optimization of the title ligands and their zinc complexes has been carried out in order to support and complement the experimental data and to further investigate the nature of the chalcogenide-metal interaction. The results show good agreement between the experimental and theoretical data. [ABSTRACT FROM AUTHOR]

At present, we investigate the mechanisms for bismuth-catalyzed direct benzylation of 2,4-pentanediones using various density functional theories and post-Hartree–Fock ab initio methods. First, we deeply consider the role of BiCl3, where six scenarios are proposed. All of them start with the formation of a weakly bound complex between the BiCl3 catalyst and the alcohol or the dione. The most favorable one corresponds to the direct access to the products via a unique transition state (SN2-type mechanism). We also examined the effects of various nonpolar and polar solvents, which are viewed to slightly affect the energy profiles for SN2 and internal nucleophilic substitution (SNi) types of mechanism, whereas strong perturbations are observed for SN1 mechanism. For instance, the later one becomes the most thermodynamically favorable in DMSO solvent. In addition, several classes of benzyl alcohols and catalysts (BiX3, where X = Cl, Br, I, NO3, and OTf) were considered within the framework of SN2 and SNi mechanisms. The reactivity of these alcohols increases going from primary to secondary to tertiary. These findings are in line with the present available experimental results. Finally, our computations suggest that Bi(NO3)3 could be an excellent catalyst for the title reaction. [ABSTRACT FROM AUTHOR]