A phosphorus-supported fluorescent probe N3P3(O2C12H8)(2)[N(Me)N=CHR](2) (RCHO = 7-diethylamino-coumarin-3-aldehyde) has been synthesized by the condensation of gem-N3P3(O2C12H8)(2)[N(Me)NH2](2) with 7-diethylamino-coumarin-3-aldehyde. This compound has been shown to be an excellent fluorescence-based chemosensor of Cu2+ and Ag+ ions in aqueous solution.