Unidirectional translocation of associated protons (with respect to the hemi-indigo scaffold) takes place during this cycle. Future efforts in our lab will focus on immobilization in porous materials and membranes of these N-heterocyclic hemi-indigos, in addition to time-resolved spectroscopic studies. Furthermore, we envision that the selective inhibition of either forwards or backwards photoisomerization paths by binding of a substrate 42 can be applied as a general approach for directional transport and pumping of that substrate. This is a tantalizing prospect, as it would give the ability to effectively generate concentration gradients in artificial systems using (solar) light as the energy source.