One-Step Electropolymerization of a Dicyanobenzene-Carbazole-Imidazole Dye to Prepare Photoactive Redox Polymer Films.

To the best of our knowledge, this study reports the first direct electropolymerization of a dicyanobenzene-carbazole dye functionalized with an imidazole group to prepare redox- and photoactive porous organic polymer (POP) films in controlled amounts. The POP films were grown on indium-doped tin oxide (ITO) and carbon surfaces using a new monomer, 1-imidazole-2,4,6-tri(carbazol-9-yl)-3,5-dicyanobenzene (1, 3CzImIPN), through a simple one-step process. The structure and activities of the POP films were investigated as photoelectrodes for electrooxidations, as heterogeneous photocatalysts for photosynthetic olefin isomerizations, and for solid-state photoluminescence behavior tunable by lithium-ion concentrations in solution. The results demonstrate that the photoredox-POPs can be used as efficient photocatalysts, and they have potential applications in sensing.

Carbazole-Cyanobenzene Dyes Electrografted to Carbon or Indium-Doped Tin Oxide Supports for Visible Light-Driven Photoanodes and Olefin Isomerizations.

The organic carbazole-cyanobenzene push-pull dye 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene was derivatized and attached to carbon or indium-doped tin oxide (ITO) electrodes by simple diazonium electrografting. The surface-bound dye is active and stable for the visible light photosynthetic isomerization of a wide range of functionalized stilbene and cinnamic acid derivatives. Up to 87,000 net turnovers were obtained for the isomerization of trans-stilbene. The isomerizations can be carried out in air with a 33% reduction in the rate. The ITO photoelectrodes are also active and stable toward photo-oxidations under basic and acidic conditions.

Solid-phase synthesis and photoactivity of Ru-polypyridyl visible light chromophores bonded through carbon to semiconductor surfaces.

1,10-Phenanthroline (phen) was grafted to either indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or titanium dioxide (TiO2) semiconductors (SC's) by electrochemical reduction of 5-diazo-phen. The phen ligand is bonded to the semiconductor at C5, and it can be handled in air. The semiconductor-phen (SC-phen) complexes displace both CH3CN ligands from either cis-[Ru(Mebipy)2(CH3CN)2]2+ (Mebipy = 4,4'-methyl-2,2'-bipyridine), cis-[Ru(tBubipy)2(CH3CN)2]2+ (tBubipy = 4,4'-tert-butyl-2,2'-bipyridine), or cis-[Ru(pheno)(bipy)(CH3CN)2]2+ (bipy = 2,2'-bipyridine; pheno = 1,10-phenanthroline-5,6-dione) dissolved in DCM/THF (4 h, 70 °C) to form the corresponding surface-bound SC-[(phen)Ru(bipyridyl)2]2+ chromophores. The identities of the SC-[(phen)Ru(Mebipy)2]2+, SC-[(phen)Ru(tBubipy)2]2+, and SC-[(phen)Ru(pheno)(bipy)]2+ (SC = ITO, FTO or TiO2) chromophores were confirmed by X-ray photoelectron spectroscopy (XPS); inductively coupled plasma mass spectrometry (ICP-MS); UV-vis and reflectance infrared spectroscopies; and cyclic voltammetry (CV). The data were compared to analogous Ru-polypyridyl control compounds dissolved in solution. A facile ketone-amine condensation solid-phase synthesis reaction between SC-[(phen)Ru(pheno)(bipy)]2+ and [Ru(1,10-phenthroline-5,6-diamine)(bipy)2]2+ in ethanol (80 °C, 1 h) formed the dinuclear, bound chromophore SC-[(phen)(bipy)Ru(tpphz)Ru(bipy)2]4+ (tpphz = tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine). Photoelectrochemical oxidation of hydroquinone and triethylamine under acidic, neutral, or basic conditions showed that the SC-chromophore photoanodes are active, and that TiO2-[(phen)Ru(Mebipy)2]2+ is the most active and stable under basic- and neutral conditions. The dinuclear chromophore SC-[(phen)(bipy)Ru(tpphz)Ru(bipy)2]4+ was most active and stable under potentiostatic conditions in acid.

Preparation and Study of Reusable Polymerized Catalysts for Ester Hydrogenation.

A cross-linked catalyst organic framework was prepared by an alternating ring-opening olefin metathesis polymerization between dichloro{N,N'-bis({(2-diphenylphosphino)phenyl}methylidene)bicyclo[2.2.1]-hept-5-ene-2,3-diamine}ruthenium, 1,2-N-di(cis-5-norbornene-2,3-endo-dicarboximido)-ethane, and cis-cyclooctene catalyzed by RuCl2(=CHPh)(PCy3)2 in the presence of a BaSO4 support. The heterogenized catalyst hydrogenated methyl benzoate at a similar rate to the homogeneous catalyst (0.0025 mol % catalyst, 10 mol % KO t Bu, 80 °C, 50 atm, tetrahydrofuran, 21 h, ∼15 000 turnovers during the first 1 h). The catalyst was used five times for a total of 121 680 turnovers. A study on the reusability of this catalyst showed that ester hydrogenations with bifunctional catalysts slow as the reaction proceeds. This inhibition is removed by isolating and reusing the catalyst, suggesting that future catalyst design should emphasize avoiding product inhibition.

Modular Construction of Photoanodes with Covalently Bonded Ru- and Ir-Polypyridyl Visible Light Chromophores.

1,10-phenanthroline is grafted to indium tin oxide (ITO) and titanium dioxide nanoparticle (TiO2) semiconductors by electroreduction of 5-diazo-1,10-phenanthroline in 0.1 M H2SO4. The lower and upper potential limits (-0.20 and 0.15 VSCE, respectively) were set to avoid reduction and oxidation of the 1,10-phenanthroline (phen) covalently grafted at C5 to the semiconductor. The resulting semiconductor-phen ligand (ITO-phen or TiO2-phen) was air stable, and was bonded to Ru- or Ir- by reaction with cis-[Ru(bpy)2(CH3CN)2]2+ (bpy = 2,2'-bipyridine) or cis-[Ir(ppy)2(CH3CN)2]+ (ppy = ortho-Cphenyl metalated 2-phenylpyridine) in CH2Cl2 and THF solvent at 50 °C. Cyclic voltammetry, X-ray photoelectron spectroscopy, solid-state UV-vis, and inductively coupled plasma-mass spectrometry all confirmed that the chromophores SC-[(phen)Ru(bpy)2]2+ and SC-[(phen)Ir(ppy)2]+ (SC = ITO or TiO2) formed in near quantitative yields by these reactions. The resulting photoanodes were active and relatively stable to photoelectrochemical oxidation of hydroquinone and triethylamine under neutral and basic conditions.

Highly Enantioselective Hydrogenation of Amides via Dynamic Kinetic Resolution Under Low Pressure and Room Temperature.

High-throughput screening and lab-scale optimization were combined to develop the catalytic system trans-RuCl2((S,S)-skewphos)((R,R)-dpen), 2-PrONa, and 2-PrOH. This system hydrogenates functionalized α-phenoxy and related amides at room temperature under 4 atm H2 pressure to give chiral alcohols with up to 99% yield and in greater than 99% enantiomeric excess via dynamic kinetic resolution.