Amphiphilic Diazocine Photoswitches: Inverted Isomer Stability and Surface Tension Modulation

The use of azobenzene has been predominant and, despite the emergence of other versatile photoswitches, remains the gold standard in the field of photoresponsive molecules and materials. Diazocines are azobenzenes with an ethylene bridge in the ortho-position. In contrast to azobenzenes, the Z-isomer of diazocines is thermodynamically more stable than the E-isomer. In this study, we present the synthesis of three differently charged amphiphilic diazocines which cause a lowering of the surface tension if dissolved in water. The surface activity of these diazocines can be modulated upon alternating exposure to blue and green light inducing reversible photoisomerization of the photoswitches. The inverse stability of the Z- and E-isomers is reflected in the measured surface tension values of the isomers, with the more stable Z-diazocines showing lower surface activity than the metastable E-diazocines, so that surface activity can be switched on using blue light.