Synthesis, photochromic properties, and light-controlled metal complexation of a naphthopyran derivative.

A light-controlled reversible binding switch based on photochromic 3H-naphtho[2,1-b]pyran is under development for studying cellular oscillatory calcium signals. The binding affinities of the closed and open forms of substituted naphthopyran 1 for Ca(2+), Mg(2+), and Sr(2+) in buffer were determined. The photochemically ring-opened form of the receptor exhibited increased affinity compared to the thermally stable closed form of the receptor. The binding affinity difference for Ca(2+) was approximately 77-fold at pH 7.6.