Photoactive chemosensors 3For Photoactive Chemosensors 1 : see ref. 13.For Photoactive Chemosensors 2: Subodh Kumar, Sukhdeep Kaur, Gurpreet Singh, Supramolecular Chemistry, 2002, in press. : a unique case of fluorescence enhancement with Cu(ii)Electronic supplementary information (ESI) available: 1. synthetic methodology and characterization of compounds. 2. Photophysical information: (a) pH titration, (b) fluorescence measurements, (c) absorption measurements. 3. Stoichiometric determination. Fig. S1: estimation of Cu(ii) in the presence of Ni(ii), Cd(ii) and Zn(ii) (10000 ??M). See http://www.rsc.org/suppdata/cc/b2/b209053h/