Figure 4.

Cyclam-based metal ion probes that incorporate a ‘click’-derived triazole as both a linker between receptor and reporter, and an additional metal-binding ligand (i.e., part of the receptor). The simple naphthalimide systems 6 and 8 respond to Zn²⁺ while coumarin 7 is a Cu²⁺/Hg²⁺ probe. The bis-naphthalimides 9 and 10 are also ‘off-on’ probes for Zn²⁺, but their fluorescence properties display markedly different solvent-dependence. Note the difference in triazole connectivity between 6 and 9 in which the naphthalimide is attached to triazole N1, versus 7, 8 and 10, in which the fluorophore is linked to C4 of the triazole.