Switching by Photochemical trans–cis Isomerization of Azobenzene Substituents in Organoplatinum Complexes

A diimine ligand, LL = 2-C₅H₄NCHN-4-C₆H₄NNPh, which carries a trans-azobenzene substituent, forms the dimethylplatinum­(II) complex [PtMe₂(LL)], which undergoes trans oxidative addition with MeI, PhCH₂Br, Br₂, and I₂ to give the corresponding organoplatinum­(IV) complexes [PtIMe₃(LL)], [PtBrMe₂(CH₂Ph)­(LL)], [PtBr₂Me₂(LL)], and [PtI₂Me₂(LL)], respectively. The ligand and the platinum­(II) and platinum­(IV) complexes are shown to undergo trans–cis isomerization of the azobenzene substituent upon irradiation, and the cis isomers then underwent slow thermal isomerization back to the more stable trans isomers.