Photocatalytic 2‐Iodoethanol Coupling to Produce 1,4‐Butanediol Mediated by TiO₂ and a Catalytic Nickel Complex

Abstract

Photocatalytic 2-iodoethanol (IEO) coupling provides 1,4-butanediol (BDO) of particular interest to produce degradable polyesters. However, the reduction potential of IEO is too negative (À 1.9 vs NHE) to be satisfied by most of the semiconductors, and the kinetics of transferring one electron for IEO coupling is slow.Here we design a catalytic Ni complex, which works synergistically with TiO 2 , realizing reductive coupling of IEO powered by photo-energy. Coordinating by terpyridine stabilizes Ni 2 + from being photo-deposited to TiO 2 , thereby retaining the steric configuration beneficial for IEO coupling. The Ni complex can rapidly extract electrons from TiO 2 , generating a low-valent Ni capable of reducing IEO. The photocatalytic IEO coupling thus provides BDO in 72 % selectivity. By a stepwise procedure, BDO is obtained with 70 % selectivity from ethylene glycol. This work put forward a strategy for the photocatalytic reduction of molecules requiring strong negative potential.