A Porphyrin-based NIR Fluorescent Probe for Bi and Potential Applications.

Herein, we have prepared a 5,10,15,20-Tetrakis(4-hydroxyphenyl) porphyrin (P) which acts as a probe for selective and sensitive detection of Bi ions. Probe P was obtained by reacting pyrrole with 4-hydroxyl benzaldehyde and characterized by NMR, IR, and ESI-MS. All photo-physical studies of P were tested in DMSO:HO (8:2, v/v) media by spectrophotometry and spectrofluorometry respectively. The selectivity of P was tested with different metal ions in solution as well as in the solid phase, only Bi showed red fluorescence quenching while with other metal ions, no such effect was observed. The Job's plot unveiled the 1:1 stoichiometric binding ratio of the probe with Bi and anticipated association constant of 3.4 ×10 M, whereas the Stern-Volmer quenching constant was noticed to be 5.6 ×10 M. Probe P could detect Bi down to 27 nM by spectrofluorometric. The binding mechanism of P with Bi was well supported with NMR, mass, and DFT studies. Further, the P was applied for the quantitative determination of Bi in various water samples and the biocompatibility of P was examined using neuro 2A (N2a) cells. Overall, probe P proves promising for the detection of Bi in the semi-aqueous phase and it is the first report as a colorimetric and fluorogenic probe.