Photocatalytic Hydroxylation of Benzene by Dioxygen to Phenol with a Cyano-Bridged Complex Containing Fe(II) and Ru(II) Incorporated in Mesoporous Silica-Alumina.
Photocatalytic hydroxylation of benzene to phenol was achieved by using O2 as an oxidant as well as an oxygen source with a cyano-bridged polynuclear metal complex containing Fe(II) and Ru(II) incorporated in mesoporous silica-alumina ([Fe(H2O)3]2[Ru(CN)6]@sAl-MCM-41). An apparent turnover number (TON) of phenol production per the monomer unit of [Fe(H2O)3]2[Ru(CN)6] was 41 for 59 h. The cyano-bridged polynuclear metal complex, [Fe(H2O)3]2[Ru(CN)6], exhibited catalytic activity for thermal hydroxylation of benzene by H2O2 in acetonitrile (MeCN), where the apparent TON of phenol production reached 393 for 60 h. The apparent TON increased to 2500 for 114 h by incorporating [Fe(H2O)3]2[Ru(CN)6] in sAl-MCM-41. Additionally, [Fe(H2O)3]2[Ru(CN)6] acts as a water oxidation catalyst by using [Ru(bpy)3](2+) (bpy = 2,2'-bipyridine) and Na2S2O8 as a photosensitizer and a sacrificial electron acceptor as evidenced by (18)O-isotope labeling experiments. Photoirradiation of an O2-saturated MeCN solution containing [Fe(H2O)3]2[Ru(CN)6]@sAl-MCM-41 and scandium ion provided H2O2 formation, where photoexcited [Ru(CN)6](4-) moiety reduces O2 as indicated by laser flash photolysis measurements. Thus, hydroxylation of benzene to phenol using molecular oxygen photocatalyzed by [Fe(H2O)3]2[Ru(CN)6] occurred via a two-step route; (1) molecular oxygen was photocatalytically reduced to peroxide by using water as an electron donor, and then (2) peroxide thus formed is used as an oxidant for hydroxylation of benzene.
Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency , Suita, Osaka 565-0871, Japan.
Yusuke
Y
Aratani
Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency , Suita, Osaka 565-0871, Japan.
Kohei
K
Oyama
Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency , Suita, Osaka 565-0871, Japan.
Tomoyoshi
T
Suenobu
Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University , Osaka 558-8585, Japan.
Yusuke
Y
Yamada
Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA and SENTAN, Japan Science and Technology Agency , Suita, Osaka 565-0871, Japan.|Department of Chemistry and Nano Science, Ewha Womans University , Seoul 120-750, Korea.|Faculty of Science and Engineering, Meijo University, ALCA and SENTAN, Japan Science and Technology Agency , Nagoya, Aichi 468-0073, Japan.
Shunichi
S
Fukuzumi