Novel and effective calcium ionbinding molecular fluorescent probes have been developed by systematic structural modification of BAPTA ionophore. The comprehensive computational studies suggested the role of the coordination number in the chelator moiety.
N′-tetraacetic acid (H4bapta), in which the distance between the chelating functions is changed, have been synthesized. The structure–interaction relationships of their complexation behavior with alkalineearth metal ions are discussed from the viewpoint of their acidity constants and stability constants of their chelate-complexes.