Phosphorus-supported multidentate coumarin-containing fluorescence sensors for Cu

Phosphorus hydrazides PhP(O)N(Me)NH₂]₂, (S)PN(Me)NH₂]₃, and N₃P₃N(Me)NH₂]₆ were condensed with 7-diethylaminocoumarin-3-aldehyde (RCHO) to afford the corresponding hydrazones PhP(O)N(Me)NCHR]₂ (1), (S)PN(Me)NCHR]₃ (2), and N₃P₃N(Me)NCHR]₆ (3). The structural characterization of 1-3 was carried out by their HRMS, ¹H and ³¹P{¹H} NMR spectra. The molecular structure of 2 was established by a single-crystal X-ray analysis. Interaction of 1 and 2 with various transition metal ions revealed substantial fluorescence enhancement upon interaction with Cu²⁺ enabling a selective detection mechanism for this metal ion. However, such a fluorescence enhancement was not observed in the case of 3. A 1:1 complex 2·Zn]ClO₄]₂·4CH₂Cl₂ was isolated in the reaction of 2 with Zn(ClO₄)₂·6H₂O. The molecular structure of this complex revealed that the Zn^II is encapsulated by the ligand utilizing a 3N, 3O coordination set.