title: A solid chelating ligand: periodic mesoporous organosilica containing 2,2'-bipyridine within the pore walls.
abstract: 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.
authors.affiliation: Toyota Central R&D Laboratories., Inc. and ‡Japan Science and Technology Agency (JST)/ACT-C, Nagakute, Aichi 480-1192, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Waki
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Maegawa
authors.forename: Kenji
authors.initials: K
authors.lastname: Hara
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Goto
authors.forename: Soichi
authors.initials: S
authors.lastname: Shirai
authors.forename: Yuri
authors.initials: Y
authors.lastname: Yamada
authors.forename: Norihiro
authors.initials: N
authors.lastname: Mizoshita
authors.forename: Takao
authors.initials: T
authors.lastname: Tani
authors.forename: Wang-Jae
authors.initials: WJ
authors.lastname: Chun
authors.forename: Satoshi
authors.initials: S
authors.lastname: Muratsugu
authors.forename: Mizuki
authors.initials: M
authors.lastname: Tada
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukuoka
authors.forename: Shinji
authors.initials: S
authors.lastname: Inagaki