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)] Pt-II and Pd-II complexes of N,N-diethyl-N'-3,4,5-trimethoxybenzoylthiourea 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.