Figure 7. Demonstration of light-controlled phase transfer.

Dynamic phase transfer of compound 8 in a toluene/aqueous NaHCO₃ (pH=9) mixture. The independent switching and phase-transfer events can be monitored by phase-colour (a) and ultraviolet-visible spectroscopy (b). Stage I: initial conditions, compound 8 resides in the organic phase (purple colour). Stage II: the azobenzene part of compound 8 was switched with irradiation at λ=365 nm. The DASA part remains untouched. Stage III: irradiation with white light results in the cyclization of the DASA moiety, decolouration and phase transfer of compound 8. Stage IV: separating the layers and back-extraction of the aqueous layer with dichloromethane results in back-transfer of compound 8 to the organic phase, as can be observed by the recolouration of this phase (purple colour). The presence of compounds in the different phases is schematically depicted (c).