Photocatalytic degradation of dichloromethane by chlorocuprate(II) ions.
Near UV irradiation of aerated solutions of (Et 4N) 2[CuCl 4] in dichloromethane causes the decomposition of CH 2Cl 2, as evidenced by the buildup of HCl, C 2H 2Cl 4, and peroxides. A net reduction to [CuCl 2] (-) occurs in the early stages, but is later reversed. In CH 2Cl 2, [CuCl 4] (2-) is in equilibrium with [Cu 2Cl 6] (2-), and only the latter species is photoactive. The decomposition is initiated by the photodissociation of chlorine atoms, which propagate to peroxy radicals, CHCl 2OO. Experimental evidence, including a linear dependence of the decomposition rate on the incident light intensity and on the fraction of light absorbed by [Cu 2Cl 6] (2-), is consistent with a mechanism in which CHCl 2OO is reduced by electron transfer from [CuCl 2] (-), following which protonation yields CHCl 2OOH. The hydroperoxide accumulates during irradiation and it too can reoxidize [CuCl 2] (-). The quantum yield for HCl production at the outset of irradiation at 313 nm is 1.3 mol/einstein, based on the fraction of light absorbed by [Cu 2Cl 6] (2-).
Doyle
Kevin J
KJ
Department of Chemistry, Santa Clara University, Santa Clara, California 95053, USA.
Tran
Huy
H
Baldoni-Olivencia
Miguel
M
Karabulut
Merve
M
Hoggard
Patrick E
PE
D000838:Anions / Q000737:chemistry; D002384:Catalysis; D002713:Chlorine / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D008024:Ligands; D008752:Methylene Chloride / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010777:Photochemistry
D000838:Anions; D008024:Ligands; D009942:Organometallic Compounds; D002713:Chlorine; D008752:Methylene Chloride; D003300:Copper