Selective colorimetric sensing and perfect linear recognition of azide: Formation of Cu-azide-Cu cascade complex within the cavity of cryptand.

Bis-trpn [tris(3-aminopropyl)amine], capped dicopper complex of bicyclic cryptand L, 1, became a potential selective colorimetric chemosensor for azide anion. Complex 1 is generating a space inside the cylindrical cavity which will be opt for perfect linear recognition of azide anion through as N-Cu⋯N⋯Cu-N axle. Naked eye colorimetric and UV-Vis spectrometric investigations shows the complex 1 has the capability of selective sensing of azide anion. The association constant and limits of detection (LoD) of complex 1 towards azide are found to be 2.754 × 10 M and 1.91 × 10 M. To the best of our knowledge, this is the first example of selective colorimetric sensing of azide by a bis‑copper cryptate 1 via ideal linear orientation of N-Cu⋯N⋯Cu-N axle inside the cylindrical shaped cavity.