Phosphorus-supported multidentate coumarin-containing fluorescence sensors for Cu2+

Phosphorus hydrazides PhP(O)[N(Me)NH2]2, (S)P[N(Me)NH2]3, and N3P3[N(Me)NH2]6 were condensed with 7-diethylaminocoumarin-3-aldehyde (RCHO) to afford the corresponding hydrazones PhP(O)[N(Me)Ndouble bond; length as m-dashCHR]2 (1), (S)P[N(Me)Ndouble bond; length as m-dashCHR]3 (2), and N3P3[N(Me)Ndouble bond; length as m-dashCHR]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 ZnII is encapsulated by the ligand utilizing a 3N, 3O coordination set.