from first principles PP-I-1

PP-V-3Dioxo-Mo(VI) - Complexes Anchored on Titania as Catalystsin Photo-Oxidative Decomposition of Some Aromatic OrganochlorineCompounds by DioxygenBakhtchadjian R.H. 1 , Tsarukyan S.V. 1 , Manucharova L.A. 1 , Tavadyan L.A. 1 , Barrault J. 21 A.B. Nalbandian Institute of Chemical Physics, NAS of Armenia, Yerevan, Republic of Armenia2 Laboratoire de Catalyse en Chimie Organique, CNRS, UMR 6503, Poitiers, Franceloriettam@yandex.ruRecently synthesized and fully characterized dioxo-Mo(VI)-dihalo[4,4’-dicarboxylato-2,2’-bypiridine] complexes anchored on the surface of titania with different characteristicparameters (specific area, porosity, size of grains) have been tested in the photochemicaloxidative decomposition of aromatic organochlorine hydrocarbonssuch as 1-chloro-4-ethylbenzene and 4,4’-dichloro-diphenylmethane.These oxidation processes under UV-irradiation or visible light maybe considered as model reactions for the degradation of persistentorganic compounds (pesticides and other organochlorine POP’s).Studies have been carried out using a photochemistry installation and elaborating a specialprotocol of reaction allowing the separation of the period of reaction between the anchoredcomplex and the substrate under UV-irradiation (λ = 254 nm) in the absence of O 2 , from theperiod of regeneration reaction between the anchored complex and O 2 in the dark. Theoxidative decomposition occurs mainly by an oxo-atom transfer to the benzylic carbon ofchlorinated aromatic hydrocarbon. In the case of 1-chloro-4-ethylbenzene, the intermediate is4’-chloroacetophenone that undergoes further decomposition to chlorobenzene, forming alsosmall amounts of oxygen-containing organochlorine compounds, CO 2 and H 2 O. Supportingevidence was obtained by submitting 4’-chloroacetophenone to the same reaction conditionsand observing the formation of chlorobenzene as a main product of its decomposition. Theratio of [final product]/ [Mo-complex] increases during the reaction up to 350–400%, whichprovides evidence of a catalytic process. It has been suggested that oxo and oxo-peroxo-Mo(VI) moieties are active centers of the reaction.The overall catalytic mechanism can be summarized as follows:1. L-(Cl) 2 Mo VI O 2 + CH 3 CH 2 C 6 H 4 Cl → L-(Cl) 2 Mo IV O + CH 3 C(OH)C 6 H 4 Cl2. L-(Cl) 2 Mo VI O 2 + CH 3 C(OH)C 6 H 4 Cl → L-(Cl) 2 Mo IV O + CH 3 C(O)C 6 H 4 Cl + H 2 O3. L-(Cl) 2 Mo IV O +O 2 → L-(Cl)2(O-O) Mo VI O (in the dark)4. L-(Cl)2(O-O) Mo VI O + CH 3 CH 2 C 6 H 4 Cl → L-(Cl) 2 Mo IV O + CH 3 C(O)C 6 H 4 Cl + H 2 O| → C 6 H 5 Clwhere L is [4,4’-dicarboxylato-2,2’-bypiridine]/TiO 2 .This work was supported by the CNRS-SCS Franco-Armenian Scientific Program.312