Selective photosensitization through an AND logic response: optimization of the pH and glutathione response of activatable photosensitizersElectronic supplementary information (ESI) available: Additional analytic and spectral data, and synthesis procedures. See DOI: 10.1039/c5cc01261a

A series of pH and GSH responsive photosensitizers were designed and synthesized. p K a values were optimized by adjusting the inductive contribution of substituents to reach a pH range (6.0-7.4) relevant to the tumour microenvironment. pH-Activatable behaviour and redox mediated release of the quencher from the PS by GSH allow the construction of an AND logic operator for selective photodynamic action in aqueous solutions. A molecular AND logic gate, which is an activatable photosensitizer, requires above-threshold values of acidity (pH) and GSH for full activity.