Porphyrin-based multi-signal chemosensors for Pb2+ and Cu2+

Two metal-free tetra(aryl) porphyrin derivatives modified by one and four N, N-bis(2-pyridylmethyl)amino group(s), namely porphyrin-1-DPA (1) and porphyrin-4-DPA (2) respectively, have been designed, synthesized, and characterized. Binding with Pb2+ induces a significant change in their solution color and in the ratio of two absorption/fluorescence signal peaks, rendering them the first example of porphyrin-based triple-signal optical sensors for Pb2+. Their dual-mode Cu2+-selective sensing properties via either the porphyrin fluorescence ON-OFF mechanism or metal displacement from the 1-Pb2+ complex that results in a triple-signal change clearly reveals their potential application as excellent and versatile sensors.