Visible Light Responsive B12-TiO2 Hybrid Catalyst Composed of Interfacial Complexation

Wednesday, 27 May 2015: 08:45
PDR 5 (Hilton Chicago)
H. Shimakoshi, S. Yonemura, and Y. Hisaeda (Kyushu University)
The CoI species of the cobalamin derivative (B12) is widely known as a supernucleophile that forms an alkylated complex by reaction with an alkyl halide.  The alkylated complex is a useful reagent for forming radical species as the cobalt-carbon bond is readily cleaved homolytically.1  Our research interest is focused on the application of this catalytic system to various molecular transformations.2  Recently, we have reported the unique catalysis of the cobalamin derivative (B12)-titanium oxide (TiO2) hybrid catalyst in which the B12 complex, cyanoaquacobyrnic acid (CoIII oxidation state), is immobilized on the surface of TiO2 and the B12 complex is reductively activated to form the CoI species by electron transfer from TiO2 under UV-light irradiation.3  The hybrid catalyst mediated the dehalogenation of various organic halides and was applied to the radical-mediated organic reaction via an alkylated complex as a catalytic intermediate.  Though the great advantage of the catalyst is the facile and efficent formation of CoI species by light irradiation, UV light irradiation was required for band gap excitation of TiO2 semiconductor.  To overcome this problem, we synthesized new B12-TiO2 hybrid catalyst (B12-TiO2-Cat) composed of interfacial complexation with catechol as shown in Figure 1a.  As a charge transfer band ascribed to catechol to TiO2 appear in visible region,4 this new hybrid catalyst is expected to work under visible light irradiation.  Futhermore, exploiting the interparticle electron transfer process in the B12-TiO2 and Cat-TiO2 combination system as shown in Figure 1b was investigated.


1. (a) Brown, K. L. Chem. Rev., 2005, 105, 2075; (b) Hisaeda, Y.; Shimakoshi, H., in Handbook of Porphyrin Science, Kadish, K. M.; Smith, K. M.; Guilard, R., Eds. World Scientific: Singapore, 2010; Vol. 10, pp 313-370.

2. (a) Jing, X.; Shimakoshi, H.; Hisaeda, Y. J. Organomet. Chem., 2015, in press; (b) Zhang, W.; Shimakoshi, H.; Houfuku, N.; Song, M.; Hisaeda, Y. Dalton Trans., 2014, 2014, 43, 13972.

3. Shimakoshi, H.; and Hisaeda, Y. et al, (a) ChemPlusChem, 2014, 79, 1250-1253 (Back cover article); (b) Chem. Commun., 2011, 6427-6429; (c) Dalton Trans, 2010, 39, 3302-3307; (d) Chem. Lett., 2009, 38, 468-469; (e) Bull. Chem. Soc. Jpn., 2010, 83, 170-172.

4. (a) Ikeda, S.; Abe, C.; Torimoto, T.; Ohtani, B. J. Photochem. Photobiol. A: Chem. 2003, 160, 61; (b) Tae, E. L.; Lee, S. H.; Lee, J. K.; Yoo. S. S.; Kang, E. J.; Yoon, K. B. J. Phys. Chem. B 2005, 109, 22513; (c) Varaganti, S.; Ramakrishna G. J. Phys. Chem. C 2010, 114, 13917; (d) Kamegawa, T. Seto, H.; Matsuura, S.; Yamashita, H. ACS Appl. Mater. Interfaces, 2012, 4, 6635.