Photoswitchable Organoplatinum(IV) Complexes

Organoplatinum­(IV)
complexes, [PtBrMe2(CH2-4-C6H4-NN-Ph)­(NN)], containing trans-azobenzene
functional groups, have been prepared by trans oxidative
addition of BrCH2-4-C6H4-NN-Ph
to the corresponding platinum­(II) complexes [PtMe2(NN)],
with NN = 2,2′-bipyridine, 1,10-phenanthroline, 4,4′-bis­(ethoxycarbonyl)-2,2′-bipyridine,
1,4-di-2-pyridyl-5,6,7,8,9,10-hexahydrocycloocta­[d]­pyridazine. The complexes undergo efficient and almost quantitative trans–cis isomerization on irradiation
of dilute solutions at 365 nm, as monitored by UV–visible spectroscopy,
and somewhat less complete photolysis in concentrated solution, as
monitored by 1H NMR spectroscopy. The cis isomers undergo slow thermal isomerization back to the trans isomers, thus proving the photoswitching property of the complexes.