ABSTRACT
We report a photocathode device consisting of GaP, a metal oxide (Al2O3 or ZnO), a phosphonate-C12-thiol monolayer, and gold nanoparticles (AuNPs). The AuNPs enhance electron transfer: in non-aqueous electrochemistry (EtV(2+) in MeCN), p-GaP|Al2O3|O3PC12S|AuNP and ZnO| |AuNP rescued the photocurrent (24%, 59% of Jmax-etch). Aqueous experiments (CO2 saturated KCl) using the optimized ZnO-functionalized device exhibited H(+) â H2 (FY = 66%) and CO2 â CO (FY = 6%).
ABSTRACT
A trinuclear nickel complex of phenanthrene-9,10-dione dioxime (H2pqd), namely bis-[µ2-9,10-bis-(oxido-imino)-phenanthrene]-bis-[µ2-10-(oxido-imino)phenanthrene-9-one oxime](phenanthrene-9,10-dione dioxime)trinickel(II) toluene disolvate, [Ni3(C14H8N2O2)2(C14H9N2O2)2(C14H10N2O2)]·2C7H8, has been isolated and its crystal structure determined. This complex features three independent Ni(II) atoms that are arranged in a triangular fashion along with five supporting ligands. There are two square-planar Ni(II) atoms and a third pseudo-octa-hedral Ni(II) atom. While the square-planar Ni(II) atoms are stacked, there are no ligand bridges between them. Each square-planar Ni(II) atom, however, bridges with the pseudo-octa--hedral Ni(II) atom through Ni-N-O-Ni and Ni-O-Ni bonds. A fluorido-bor-ation reaction of the proton-bridged species gave the analogous complex bis-(µ2-bis-{[10-(oxido-imino)-9,10-di-hydro-phenanthren-9-yl-idene]amino}di-fluorido-borato)(phenanthrene-9,10-dione dioxime)trinickel(II) dichloromethane trisolvate, [Ni3(C28H16BF2N4O2)4(C14H10N2O2)]·3CH2Cl2, which shows the same binding structure, but features a widened Ni-Ni inter-action between the square-planar Ni(II) atoms. The proton-bridged complex completes the macrocyclic coordination around the square-planar Ni(II) atoms by means of an O-Hâ¯O hydrogen bond. Both compounds feature O-Hâ¯N hydrogen bonds between the oxime and the N atoms attached to square-planar nickel atom. The nickel units show no direct inter-action with their nearest neighbors in the extended lattice. Two π-stacking inter-actions between adjacent mol-ecules are found: one with a centroid-centroid distance of 3.886â (2)â Å and the other with a centroid-centroid distance of 4.256â (3)â Å. In the latter case, although not aromatic, the distance to the centroid of the central phenanthrene ring is shorter, with a distance of 3.528â (3)â Å. Toluene mol-ecules occupy the solvent channels that are oriented along the c axis. In the fluorido-boronate structure, the solvent (DCM) was too badly disordered to be modelled, so its contribution was removed using SQUEEZE [Spek (2015 â¸). Acta Cryst. C71, 9-18].
ABSTRACT
Reported here are the syntheses and characterization of cobaloximes that feature a bis(imino)acenaphthene (BIAN) appended ligand. The X-ray crystal structures and spectroscopy ((1)H NMR or EPR) of the complexes within the series [Co(aqdBF2)2(MeCN)2] (), [Co(aqdBF2)(MeCN)2](-) () and [Co(aqdBF2)2(MeCN)2](2-) (, ) are reported and the 3-electron reduced complex [Co(aqdBF2)2(MeCN)2](3-) () has been prepared in situ and characterized by (1)H NMR spectroscopy. The X-ray crystal structures revealed the presence of a 6-coordinate Co(II) species (), a 5-coordinate Co(I) species (), and a 4-coordinate complex (, ). In the case of complex , evidence from single crystal EPR spectroscopy (gâ = 2.017, g⥠= 1.987; <10 G linewidths) in conjunction with DFT calculations indicate that the EPR signal originates from a delocalized ligand-based unpaired spin. The frontier orbitals obtained from DFT calculations on , , , & support the electronic assignments that were observed spectroscopically. The cathodic cyclic voltammogram (CV) of the solvato congener in DMF solution, namely [Co(aqdBF2)2(DMF)2], exhibits three reversible redox events near -1.0, -1.5 and -2.0 V vs. Fc/Fc(+). Catalytic proton reduction was observed by CV near the third redox peak. Compared with other cobaloximes (Ecat = -1.0 V), the delay of catalytic onset arises from the existence of a series of resonance-stabilized intermediates.
