Photoinduced isomerisation of cis-[M(L-S,O)2](M = PtII and PdII) complexes of N,N-diethyl-N-3,4,5-trimethoxybenzoylthiourea: key to preparation of the trans isomer

In acetonitrile solutions at room temperature, cis-[M(L-S,O)2] PtII and PdII complexes of N,N-diethyl-Nʹ-3,4,5trimethoxybenzoylthiourea undergo reversible photoinduced isomerisation to the corresponding trans isomer upon irradiation with visible light in the 320–570 nm range, the rate and extent of isomerisation being significantly higher for the cis-[Pd(L-S,O)2] complex compared to the PtII analogue; in the dark trans-[M(L-S,O)2] cleanly reverts back to the cis complex at a rate dependent on the solution temperature, indicating a thermally controlled reverse process.