A tetra-nuclear Cu( ii ) complex of amide-imine conjugate: highly-selective ESIPT-based probe for OCl −

Single crystal X-ray structurally characterized, tetra-nuclear Cu( ii ) complex (C1) experiences turn ON fluorescence in presence of OCl as low as 13.87 nM. The proposed H-bond-assisted inhibition of the ESIPT provides the binding constant, 1.52 × 10 5 M −1 .