Efficient Sensitized Z→E Photoisomerization of an Iridium(III)-Azobenzene Complex over a Wide Concentration Range.

To improve the sensitized Z -> E photoisomerization of azobenzenes, and circumvent the threshold concentration necessary for the bimolecular photoinduced electron transfer reaction to generate the rapidly isomerizing Z-azo-benzene radical anion, an Ir-III complex with a covalently tethered azobenzene fragment was synthesized. Selective irradiation of the (MLCT)-M-1 band of the Ir-III complex induced an efficiently sensitized photoswitching of the dyad over a wide concentration range and even at high dilution.