Synthesis and metal binding properties of N -alkylcarboxyspiropyrans.

Spiropyrans bearing an N -alkylcarboxylate tether are a common structure in dynamic, photoactive materials and serve as colourimetric/fluorimetric cation receptors. In this study, we describe an efficient synthesis of spiropyrans with 2-12 carbon atom alkylcarboxylate substituents, and a systematic analysis of their interactions with metal cations using ¹ H NMR and UV-visible spectroscopy. All N -alkylcarboxyspiropyrans in this study displayed a strong preference for binding divalent metal cations and a modest increase in M ²⁺ binding affinity correlated with increased alkycarboxylate tether length.