Synthesis of a solid chelating ligand for the formation of efficient heterogeneous catalysts is highly desired in the fields of organic transformation and solar energy conversion. Here, we report the surfactant-directed self-assembly of a novel periodic mesoporous organosilica (PMO) containing 2,2'-bipyridine (bpy) ligands within the framework (BPy-PMO) from a newly synthesized organosilane precursor [(i-PrO)3Si-C10H6N2-Si(Oi-Pr)3] without addition of any other silane precursors. BPy-PMO had a unique pore-wall structure in which bipyridine groups were densely and regularly packed and exposed on the surface. The high coordination ability to metals was also preserved. Various bipyridine-based metal complexes were prepared using BPy-PMO as a solid chelating ligand such as Ru(bpy)2(BPy-PMO), Ir(ppy)2(BPy-PMO) (ppy = 2-phenylpyridine), Ir(cod)(OMe)(BPy-PMO) (cod = 1,5-cyclooctadiene), Re(CO)3Cl(BPy-PMO), and Pd(OAc)2(BPy-PMO). BPy-PMO showed excellent ligand properties for heterogeneous Ir-catalyzed direct C-H borylation of arenes, resulting in superior activity, durability, and recyclability to the homogeneous analogous Ir catalyst. An efficient photocatalytic hydrogen evolution system was also constructed by integration of a Ru-complex as a photosensitizer and platinum as a catalyst on the pore surface of BPy-PMO without any electron relay molecules. These results demonstrate the great potential of BPy-PMO as a solid chelating ligand and a useful integration platform for construction of efficient molecular-based heterogeneous catalysis systems.

Ni-ceria nanoparticles (Ni/Ce = 1/1) in the cage-like pores of SBA-16 were prepared and evaluated in methane dry reforming reactions. Coexistence of ceria in NiCe/SBA-16 resulted in forming uniformly sized Ni particles (av. 5.7 nm) within the mesopores of SBA-16, because of the confinement effect from the framework of SBA-16 and the strong interaction between Ni and ceria. Ceria addition facilitated the reduction of NiCe/SBA-16 compared with Ni/SBA-16, and Ce3+ was the dominant species in both fresh and used NiCe/SBA-16 catalysts, as determined by Ce LIII-edge X-ray absorption near-edge structure (XANES). The methane conversion was much more stable on NiCe/SBA-16 than on Ni/CeO2 and Ni/SBA-16 in the methane dry reforming at 973 K during a 100 h reaction period; the deactivation of the Ni catalyst and the collapse of the SBA-16 framework were preferably suppressed for NiCe/SBA-16 under the reaction conditions. The remarkable effect of ceria on the structural stability of both the active Ni particles and the SBA-16 framework led to the consistent catalytic performance of NiCe/SBA-16 in methane dry reforming.

We report the N-heterocyclic carbene (NHC)-induced activation of an otherwise unreactive Pd/AlO catalyst. Surface analysis techniques demonstrate the NHC being coordinated to the palladium particles and affecting their electronic properties. Ab initio calculations provide further insight into the electronic effect of the coordination with the NHC injecting electron density into the metal nanocluster thus lowering the barrier for bromobenzene activation. By this NHC modification, the catalyst could be successfully applied in the Buchwald-Hartwig amination of aryl chlorides, bromides, and iodides. Various heterogeneity tests could additionally show that the reaction proceeds via a heterogeneous active species.

Here we report, for the first time, an extensive characterization of an N-heterocyclic carbene (NHC)-modified supported heterogeneous catalyst. The existence of the metal-carbene bond could be proven by (13)C-SS-NMR experiments. Furthermore, it could be shown that the modification with NHCs does not structurally change the catalyst itself. The effect of the nature and the loading of the NHC on the activity and selectivity of the heterogeneous catalyst is presented by a hydrogenation study, finally leading to an NHC-enabled tunable heterogeneous catalyst for chemoselective hydrogenation.

A simple and efficient synthetic method for preparing high-surface-area perovskites was investigated by focusing on the importance of the formation of an amorphous precursor. Hexagonal SrMnO 3 with high surface area was successfully synthesized by simple calcination of the amorphous precursor prepared using aspartic acid and metal acetates instead of metal nitrates, without pH adjustment. The specific surface area reached up to ca. 50 m 2 g −1 , which is much larger than that for SrMnO 3 synthesized by previously reported methods. The catalytic activity for heterogeneous liquid-phase aerobic oxidation was significantly improved in comparison with the polymerized complex method, and the present catalytic system was applicable to the oxidation of various substrates. ■ INTRODUCTIONPerovskite-type oxides with the general formula ABO 3 are a class of mixed oxides that exhibit compositional and structural varieties. The versatility and accessibility of perovskite-type oxides have attracted significant interest in broad fields of piezoelectric, ferroelectric, (anti)ferromagnetic, catalytic, and semiconducting materials. 1 A number of methods for the synthesis of perovskites, such as solid-state, coprecipitation, sol−gel, hydrothermal, freeze/spray drying, and microwave methods, have been developed. 2 In particular, an increase of surface area is important for catalytic applications, and many efforts have been made to synthesize nanoperovskites with high surface areas. The sol−gel methods represented by the Pechini method and polymerized complex (PC) method are among the most studied and frequently used techniques for the preparation of nanoperovskites because these methods can accurately control the final composition and yield pure and homogeneous perovskites. 3 However, these methods have some disadvantages in that they are (i) complicated procedures that include complex and polymer gel formation, pyrolysis to an amorphous precursor, and calcination and they require (ii) the use of toxic ethylene glycol and significant amounts of organic reagents and (iii) high-temperature calcination to remove carbonates formed from the carbonaceous precursors, which results in low specific surface area. In addition, the combustion of carbon species elevates the temperature of the material itself and further sinters the material, which decreases the surface area. Therefore, the development of simple and efficient synthesis methods to obtain highly homogeneous and dispersed perovskite nanomaterials with high surface area is still strongly required and a challenging research subject.We have recently reported that hexagonal SrMnO 3 (SMO-PC) synthesized by the PC method with a surface area of 25 m 2 g −1 can act as an efficient reusable heterogeneous catalyst for the selective liquid-phase oxidation of various organic substrates with O 2 . 4 The synthesis of high-surface-area SMO can improve its catalytic activity. Teraoka and co-workers reported La 0.8 Sr 0.2 MO 3 (M = Mn and Co) with high surface area (37 and 20 m 2 g −1 , respectively)...

Electronic conductivity of molecular wires is a critical fundamental issue in molecular electronics. pi-Conjugated redox molecular wires with the superior long-range electron-transport ability could be constructed on a gold surface through the stepwise ligand-metal coordination method. The beta(d) value, indicating the degree of decrease in the electron-transfer rate constant with distance along the molecular wire between the electrode and the redox active species at the terminal of the wire, were 0.008-0.07 A(-1) and 0.002-0.004 A(-1) for molecular wires of bis(terpyridine)iron and bis(terpyridine)cobalt complex oligomers, respectively. The influences on beta(d) by the chemical structure of molecular wires and the terminal redox units, temperature, electric field, and electrolyte concentration were clarified. The results indicate that facile sequential electron hopping between neighboring metal-complex units within the wire is responsible for the high electron-transport ability.

Surface junction effects on the electron conduction of p-phenylene-bridged bis(terpyridine)iron oligomers terminated with a ferrocene moiety were quantitatively analyzed by employing three different surface-anchoring terpyridine ligands. The dependence of the electron-transfer rate constant for oxidation of the ferrocene moiety, k(et), on the distance between the electrode surface and the ferrocene moiety, x, showed that the attenuation factor, beta(d), which indicates the degree of reduction of k(et) with x, was approximately 0.018 in all cases. However, the absolute k(et) value depended strongly on both electronic and steric factors of the surface-anchoring ligand.

We synthesized ferrocene-attached dimethyldihydropyrene (DHP) derivatives and investigated their photochemical and redox behaviors. For bis(ferrocenylethynyl)dimethyldihydropyrene (1), reversible photoisomerization between the closed DHP form (1c) and the open CPD form (1o) occurred in high yields upon alternate irradiation of visible (578 nm) light and UV (303 nm) light, whereas no photoisomerization proceeded for bis(pentamethylferrocenylethynyl)dimethyldihydropyrene (2). 1 exhibited reversible switching of electronic communication between the ferrocene (Fc) moieties by photoisomerization of the DHP moiety and demonstrated a novel ring closing reaction induced by oxidation of the Fc moieties. The magnitude of electronic communication, deltaE0' (the difference between the redox potentials of two Fc's), was 63 mV in 1c and 16 mV in 1o, indicating that the electronic communication through the spacer is enhanced in the more developed pi-conjugation of the DHP moiety. The rate constants of the ring closing reaction from 1o+ to 1c+ and from 1o2+ to 1c2+ were estimated at 3.7 and 0.50 s(-1), respectively, by the simulation of cyclic voltammograms.