A novel fluorescent chemosensor for Cu(II) in aqueous solution based on a β-aminobisphosphonate receptor

A novel β-aminobisphosphonate receptor has been combined with naphthalene in the fluorophore–spacer–receptor format of a typical photoinduced electron transfer (PET) based sensor. The sensor was synthesised in two steps by first reacting aminomethylnaphthalene with diethyl vinylphosphonate to produce the parent tetraester, followed by deprotection with bromotrimethylsilane to afford the desired sensor. The fluorescence emission of the sensor was observed to remain ‘On’ over a wide pH range (2–10). Cu(II) was found to bind strongly to the sensor resulting in an ‘On–Off’ fluorescent response with sensitivity in the μM range.