Manganese(II) Complexes with Schiff Bases Immobilized on Nanosilica as Catalysts of the Reaction of Ozone Decomposition

In this article, we submit the description of synthesis and identification of manganese(II) complexes with pyrogenic nanosilica-immobilized (d av = 10 nm; S sp = 290 m2/g) hydroxyaldimine ligands (Mn(L)2/Si): salicilaldiminopropyl (L1); 5-bromosalicilaldiminopropyl (L2); 2-hydroxynaphtaldiminopropyl (L3); 2-hydroxy-3-methoxybenzaldiminopropyl (L4); 2-hydroxy-3,5-dichloroacetophenoniminopropyl (L5); and 4-hydroxy-3-methoxybenzaldiminopropyl (L6). The ligands and complexes were characterized by UV-VIS and IR spectrometry. Nanocomposites consisting of complexes Mn(L)2/Si showed a high catalytic activity in low-temperature ozone decomposition in the range of concentrations between 2.1 × 10−6 and 8.4 × 10−6 mol/l. The number of catalytic cycles increased for isostructural pseudotetrahedral complexes Mn(L)2/Si (L1–L5) in the following order: Mn(L3)2 >> Mn(L4)2 > Mn(L1)2 > Mn(L2)2 > Mn(L5)2. In the case of pseudooctahedral complexes with L6, the change of coordination polyhedral does not influence the kinetics and stoichiometric parameters of the reaction

Synthesis and (spectro)electrochemical investigations of coordinatively-saturated (cyclopentadienyl)ruthenium-Hantzsch pyridinium/dihydropyridine conjugates

Complexes with the CpRu(PPh3) fragment bound by iminopyridine ligands functionalised by a Hantzsch dihydropyridine donor of hydride ion or by a Hantzsch pyridinium acceptor of hydride ion have been prepared, and their redox chemistry studied by cyclic voltammetry and EPR and UV-Vis spectroelectrochemical investigations. These Ru(II) complexes have a coordinatively saturated, electronically precise (18-electron) ruthenium(II) centre with a non-labile ligand donor set, which suppresses complicating metal-centred reactivity and, thereby, allows the baseline physicochemical properties of the Hantzsch dihydropyridine/pyridinium-functionalised ligands to be investigated. In Ru(II) complexes, the iminopyridine chelate is linked to the Hantzsch pyridine groups by either an ortho-phenyl bridge (electronically delocalized) or by a meta-phenyl bridge (electronically isolated), which leads to notable differences in spectroscopic properties, even for ruthenium centre, and differences in redox reactions. Of note, the primary electrochemical reduction of the Ru(II) complexes with a Hantzsch pyridinium substituent is centred on this group, but did not afford the corresponding Ru(II) complexes with a 1,4-dihydropyridine substituent. Rather it was found that the reduction products were identical to the 1:1 hydroxide adducts formed upon addition of hydroxide ion to the starting Hantzsch pyridinium-substituted Ru(II) complexes. Based on these results and comparisons with data from the literature, the reduction products and hydroxide adducts are tentatively assigned as the corresponding hydroxy-dihydropyridine substituted Ru(II) complexes (during reduction, hydroxide ion was likely formed from the residual water present in the acetonitrile solvent). Implications for the electrochemical cycling of transition metal catalysts with Hantzsch pyridinium/dihydropyridine functional substituents are considered

Functionalization of a diacetylene on the mixed-chalcogenide compound fe2(co)6(mu-ste) - structural characterization of (co)6fe2(mu-sc(c-equivalent-to-cch3)=c(h)te)

The room-temperature reaction of the mixed-chalcogenide complex Fe2(CO)6(mu-STe) with the diacetylene CH3C=CC=CH forms the new compound (CO)6Fe2{mu-SC(C=CCH3)=C(H)Te}. The structure of (CO)6Fe2{mu-SC(C=CCH3)=C(H)Te} has been established by single-crystal X-ray diffraction methods: P1BAR, a = 6.587(2) angstrom, b = 10.689(3) angstrom, c = 11.067(3) angstrom, alpha = 92.74(2)-degrees, beta = 92.77(2)-degrees, gamma = 97.23(2)-degrees, V = 771(3) angstrom3, Z = 2, R = 5.6%, R(w) = 6.8%. Molecular orbital calculations have been performed on the four possible isomers of (CO)6Fe2{mu-SC(C=CCH3)=C(H)Te} which can be expected to form, and the formation of the experimentally found isomer has been rationalized

Topochemical dimerization of non-parallel double bonds: 7-methoxycoumarin

X-ray crystal structure analysis of 7-methoxycoumarin reveals that the reactive double bonds are rotated by about 65° with respect to each other, the centre-to-centre distance between the double bonds being 3.83 Å. In spite of this unfavourable arrangement, photodimerization occurs in the crystalline state yielding the syn-head-tail dimer as the only product. Lattice energy calculations on ground-state molecules in crystals throw light on the mechanism of the reaction

Strain assisted .alpha.-cleavage reactions of thio ketones: diphenylcyclopropenethione

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Structure of pentacyclo[7.4.2.02,6.06,15.011,14]pentadec-4-ene-7,13-dione, a novel pentacyclic C15 quinane system

C 15H 1602 (a synthetic precursor to dodecahedrane), monoclinic, P21/n, a = 12.171 (5), b = 6.976(5), c = 13.868 (3) A, B = 102.56 (3) ° , Z = 4, D m = 1.30, D c = 1.318 g cm -3, F(000) = 488, g(Mo K¢t) = 0.92 cm- 1. Intensity data were collected on a Nonius CAD-4 diffractometer and the structure was solved by direct methods. Full-matrix least-squares refinement gave R = 0.077 (R w = 0.076) for 1337 observed reflections. All the five-membered rings are cis fused and have envelope (C s symmetry) conformations

Macrocyclic bis(phenanthroline-pyrrole): A convenient one-pot synthesis, structure(s), spectroscopic, and redox properties, and the binding of amine guests, protons, and lanthanide ions

This paper reports a convenient, one-pot, easily scalable and readily modifiable synthesis of a novel large-ring bis(1,10-phenanthrolinyl-2,5-pyrrole) macrocycle, H2LMC, and describes its spectroscopic and electrochemical properties, protonation, cooperative amine binding, electrocatalysis of the oxidation of primary amines, photosensitization of the decomposition of dichloromethane, and the first lanthanide complexes of the hexaaza-dianion LMC2- including the novel dimer, [(NO 3)(LMC)Eu(μ-OH)Eu(LMC)(H2O) 2]×2py. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Bio-inspired transition metal-organic hydride conjugates for catalysis of transfer hydrogenation: Experiment and theory

Taking inspiration from yeast alcohol dehydrogenase (yADH), a benzimidazolium (BI+) organic hydride-acceptor domain has been coupled with a 1,10-phenanthroline (phen) metal-binding domain to afford a novel multifunctional ligand (LBI+) with hydride-carrier capacity (LBI+ + H-⇌LBIH). Complexes of the type [Cp∗M(LBI)Cl][PF6]2 (M = Rh, Ir) have been made and fully characterised by cyclic voltammetry, UV/Vis spectroelectrochemistry, and, for the IrIII congener, X-ray crystallography. [Cp∗Rh(LBI)Cl][PF6]2 catalyses the transfer hydrogenation of imines by formate ion in very goods yield under conditions where the corresponding [Cp∗Ir(LBI)Cl][PF6] and [Cp∗M(phen)Cl][PF6] (M = Rh, Ir) complexes are almost inert as catalysts. Possible alternatives for the catalysis pathway are canvassed, and the free energies of intermediates and transition states determined by DFT calculations. The DFT study supports a mechanism involving formate-driven Rh-H formation (90 kJ mol-1 free-energy barrier), transfer of hydride between the Rh and BI+ centres to generate a tethered benzimidazoline (BIH) hydride donor, binding of imine substrate at Rh, back-transfer of hydride from the BIH organic hydride donor to the Rh-activated imine substrate (89 kJ mol-1 barrier), and exergonic protonation of the metal-bound amide by formic acid with release of amine product to close the catalytic cycle. Parallels with the mechanism of biological hydride transfer in yADH are discussed

Sugar-substituted fluorous 1,2,3-triazoles: Helical twists in fluoroalkyl chains and their molecular association in the solid state and correlations with physicochemical properties

This paper describes a novel study of thirty closely related polyfluoroalkyl-substituted glycosidyl-1,2,3-triazoles with systematic variations in the type of sugar, D-glucos-1′-yl or D-galactos-6′-yl derivatives, the protected or unprotected form of the sugar, the length and nature of linker groups to the triazole, the point of attachment and the atom of attachment between the substituent and the triazole, and the length of the perfluoroalkyl chain. It reports for the first time the molecular structure and crystal structures of three of the candidates, as defined by single crystal X-ray diffraction analysis, and compares melting point and specific optical rotation values, in combination with the diffraction, NMR spectroscopic and computational data to establish structural features, such as the helical twist of the fluoroalkyl chains, that influence physicochemical properties in the solid and solution states. The results provide a valuable reference source for practitioners in the field and will aid in the design of future materials