Dechlorination of DDT catalyzed by visible-light-driven system composed of vitamin B₁₂ derivative and Rhodamine B

Abstract

The visible-light-driven dechlorination of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) was carried out in the presence of a hydrophobic vitamin B12 , heptamethyl cobyrinate perchlorate and Rhodamine B . DDT was successfully dechlorinated to form 1,1-bis(4-chlorophenyl)-2,2-dichloroethane (DDD) as the mono-dechlorinated product upon visible light irradiation with a tungsten lamp (λ > 440 nm). Upon prolonged visible light irradiation to DDT, DDMU (1-chloro-2,2-bis(4-chlorophenyl)ethylene), DDMS (1-chloro-2,2-bis(4-chlorophenyl)ethane) and DCS (trans-4,4′-dichlorostilbene) were obtained as the di- and tri-dechlorinated products. The use of the photostable organic sensitizer enabled prolonged photocatalysis via a noble-metal-free process. The vitamin B12 derivative was replaced by an imine/oxime-type cobalt complex although the cobalt complex system showed a lower catalytic activity than the B12 derivative system. The dechlorination mechanism in the B12 -Rhodamin B system was investigated by various methods such as UV-vis absorption and fluorescence quenching.

Vitamin B12catalysed reactions

“…This reaction can be achieved in EtOH, ionic liquid, and in heterogenic reaction with B 12 and Ru catalysts supported on a metal-organic framework (MOF) under mild conditions (Scheme 12). [23][24][25] Hisaeda then superseded that work by using cobyrinic acid as both a catalyst and a photosensitiser under UV irradiation. 23 Note that here, the catalyst must already be in the reduced Co(II) form.…”