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Tungsten carbide-based nano-catalysts (Ni-WC, Co-WC and NiCo-WC) and molybdenum carbide-based nano-catalysts (Ni-MoC, Co-MoC and NiCo-MoC) were synthesised using a carbothermal reduction method. X-ray diffraction, scanning electron microscopy coupled with electron dispersive spectroscopy, x-ray photoelectron spectroscopy and cyclic voltammetry were used to evaluate the prepared electrocatalysts. The cyclic voltammetry results showed that Ni-WC coated electrode displayed the best hydrogen evolution reaction catalytic activity with the lowest overpotential of 1.421 V at a current density of 10 mA cm−2, and a Tafel slope of 135 mV dec−1 which is marginally lower than the benchmark Pt/C coated electrodes. Ni-MoC and Co-MoC coated electrocatalysts also produced current more effectively with a change in potential as compared to the Pt/C coated electrode. The durability test showed Co-WC, NiCo-WC and Ni-MoC coated electrodes to have high stability within a wide range of current densities. [ABSTRACT FROM AUTHOR]

A new synthetic route involving ligand exchange towards a series of ruthenocenyl-containing β-diketonato titanocene complexes of the type [Ti IV (C 5 H 5 ) 2 (RcCOCHCOR)][ClO 4 ] with Rc = Ru II (C 5 H 5 )(C 5 H 4 ) and R = C 10 F 21 ( 1 ), CF 3 ( 2 ), C 6 F 5 ( 3 ), C 10 H 21 ( 4 ), CH 3 ( 5 ), Rc ( 6 ) and Fc = Fe II (C 5 H 5 )(C 5 H 4 ) ( 7 ) are described. The complex [Ti IV (C 5 H 5 ) 2 (RcCOCHCOCH 3 )][ClO 4 ], 5 , (Z = 4) crystallised in the monoclinic space group P2 1 /n. A cyclic voltammetric electrochemical study in CH 2 Cl 2 /0.1 M [NBu 4 ][B(C 6 F 5 ) 4 ] showed the one-electron transfer redox processes of the Ti III /Ti IV and Rc/Rc + couples exhibited irreversible electrochemical behaviour. In CH 3 CN/0.1 M [N( n Bu) 4 ][PF 6 ], the ruthenocenyl couple switched to an electrochemically and chemically irreversible two-electron transfer redox couple, Rc/Rc 2+ , involving the Ru IV redox centre. The redox potentials of the Ti III /Ti IV , Rc/Rc + and Rc/Rc 2+ couples were in the range −642 < E o′ < −1479 mV (both solvents), 1016 mV < E o′ < 1034 mV (CH 2 Cl 2 ) and 609 mV < E o′ < 832 mV (CH 3 CN) vs . the free ferrocene couple, FcH/FcH + , respectively. The Fc/Fc + redox process associated with 7 was observed at E o′ = 0.259 (CH 3 CN) and 0.235 V (CH 2 Cl 2 ). The cytotoxicity of [Ti IV (C 5 H 5 ) 2 (RcCOCHCOCF 3 )][ClO 4 ], 2 , against CoLo DM320 and HeLa cells, IC 50 = 10.2 and 9.7 μmol dm −3 respectively, was found to be in the same order of magnitude as those of the free ligand, RcCOCH 2 COCF 3 . [ABSTRACT FROM AUTHOR]

Abstract: Chalcones of the type Mc-CO–CH-CO–CH Mc-CO–CHh Mc=Fc=ferrocenyl or Rc=ruthenocenyl, and Ph=phenyl were synthesized. Synthesis was achieved by base catalyzed Claisen–Schmidt condensation of the appropriated acetyl and aldehyde in ethanol. Cyclic voltammetry in CH3CN in the presence of 0.1moldm−3 [N(Bu)4][PF6] revealed chemical and electrochemical reversible behaviour for the Fc/Fc+ couple and irreversible electrochemistry for the two electron Rc/Rc2+ couple. The potential ranges for the Fc/Fc+ couple varied in the range 138⩽ E°′⩽302mV while E pa for Rc/Rc2+ couple was between 358 and 510mV vs. FcH/FcH+, the internal standard. Chalcones with the carbonyl group adjacent to the metallocene, are more difficult to oxidize. [Copyright &y& Elsevier]

Abstract: The synthesis of a variety of tetrahedral β-diketonato titanium(IV) complexes of the type with R=CF3, OCH3, C6H5, CH3 and Fc is described. The TiIII/TiIV couples and the Fc/Fc+ couple exhibited chemically and electrochemically reversible cyclic voltammetric behaviour. The formal reduction potential of the TiIII/IV couple increased as the group electronegativity of the R group of the β-diketonato ligand increased. Bulk electrolysis showed that one electron was transferred in the TiIII/IV couple and one electron in the ferrocenyl/ferrocenium redox couple in the ligand. The crystal structure for the R=OCH3 complex showed that this β-keto-ester binds through the carbonyl oxygen of the ester group and not the ether oxygen. [Copyright &y& Elsevier]

[Display omitted] Three different classes of ferrocenyl-containing β-keto compounds Fc-CO-CH 2 -CO-R were synthesised to obtain two β-diketones with R = CH 3, 3 , and R = Fc (ferrocenyl = FeII(C 5 H 5)(C 5 H 4)), 4 , a β-ketoester, 5 , with R = OEt and a β-ketoamide, 6 , with R = NH 2. The β-diketones exhibited keto ⇌ enol tautomerization with the enol form Fc-CO-CH=C(OH)-R as the dominant isomer. Both the β-ketoester and β-ketoamide primarily existed in the keto form. FTIR and 1H NMR measurements could distinguish between keto and enol isomers. Dilute CHCl 3 solutions of 3 and 4 exhibited FTIR ѵ C=O keto vibrations between 1627 and 1712 cm−1 and ѵ C=O enol vibrations between 1590 and 1660 cm−1. X-ray photoelectron spectroscopic (XPS) measurements showed keto isomer Fe 2p 3/2 photoelectron lines at smaller binding energies than enol isomers. Significantly lower calculated molecular energies of the keto form of the β-ketoester 5 and β-ketoamide 6 utilising the Gaussian09 suite of programs at the B3LYP (uB3LYP for open-shell species), confirmed that 5 and 6 almost exclusively exists in the keto conformation. Cyclic voltammetry also distinguished between keto and enol isomers, and it was found that the electrochemical reversible ferrocenyl formal oxidation potential, E °ꞌ, of keto isomers of compounds can be estimated with the equation E °ꞌ keto = 170.99χ R –57.57 where χ R is the group electronegativities of R in FcCOCH 2 COR. This result complements earlier research that enables calculation of the ferrocenyl formal oxidation potentials of enol isomers of β-diketones. Computational studies further showed that the HOMO orbitals of 3 – 6 is exclusively on the Fe centre and computed Mulliken spin densities on the d xy orbital of the oxidised iron species approached 1 e−. [ABSTRACT FROM AUTHOR]

Abstract: A comparative investigation of seven ferrocene-containing chalcones (Fc–CO–CH;C6H4R, with R=OCH3, CH3, Ph, t Bu, H, Br and CF3) has been performed based on their electrochemical and spectroscopical behavior as well as with DFT calculations. These compounds were prepared by Claisen-Schmidt condensation of acetylferrocene and the appropriate benzaldehyde derivative. All compounds exhibited reversible chemical and electrochemical behavior, as confirmed by ΔE =83−93mV and i pc/i pa =0.93−1.00. The formal reduction potential E°′ for the compounds ranged between 231.0 and 261.5mV versus FcH/FcH+ as an internal standard. The UV–Vis spectra of all ferrocene-containing chalcones showed the characteristic peaks for aromatic systems at ±380nm and a peak in the visible region at ±490nm, which is attributed to the ferrocene moiety. FTIR of all the ferrocene-containing chalcones showed a characteristic CO stretching peak at ±1650cm−1. DFT calculated HOMO energies and ionization potentials correlate well with experimentally measured E°′ values. [Copyright &y& Elsevier]