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

A diimine ligand, LL = 2-C 5 H 4 NCH═N-4-C 6 H 4 N═NPh, which carries a trans -azobenzene substituent, forms the dimethylplatinum(II) complex [PtMe 2 (LL)], which undergoes trans oxidative addition with MeI, PhCH 2 Br, Br 2, and I 2 to give the corresponding organoplatinum(IV) complexes [PtIMe 3 (LL)], [PtBrMe 2 (CH 2 Ph)(LL)], [PtBr 2 Me 2 (LL)], and [PtI 2 Me 2 (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.