A Mercurated Azobenzene Complex for Photoswitching between trans and cis Forms

A pro-mesogenic compound based on an ortho-mercurated derivative of the azobenzene chromophore undergoes reversible trans-cis photoisomerization. By exploiting the spectral features of the orthometalated cis and trans isomers it is possible to produce photostationary states containing 78 and 90% of trans (rod-like, bright yellow) and cis (bent, colourless) isomers, respectively, which may be the basis for an efficient all-optical control of ON/OFF liquid crystalline behaviour.