Azacrown[N,S,O]-modified porphyrin sensor for detection of Ag+, Pb2+, and Cu2+.

One new azacrown[N,S,O]-modified metal-free porphyrin derivative, H2Por-azacrown (1), with the central tetrapyrrole moiety as signaling fluorophore and/or metal ion receptor has been designed, synthesized, and characterized. Addition of Ag(+) into this novel metal-free porphyrin compound induces a fluorescence ON-OFF process, while adding Pb(2+) leads to absorption/emission-ratiometric signals. Quite interestingly, blue-shift of the Soret band, ratiometric change of Q bands, and dual-signal changes (absorption ratio and fluorescence ON-OFF) associated with the Cu(2+) displacement from the 1-Pb(2+) system were observed upon addition of Cu(2+). These results render this H2Por-azacrown compound a porphyrin-based multi-responsive optical sensor towards Ag(+), Pb(2+), and in particular Cu(2+) with dual-mode detecting potential.