Rhodamine-based Cu2+-selective fluorosensor: synthesis, mechanism, and application in living cells.

A rhodamine B-based fluorescence probe (1) for the sensitive and selective detection of Cu(2+) ion has been designed and synthesized using pyridine moiety. The optical properties of this compound have been investigated in acetonitrile-water binary solution (7:3 v/v). Compound 1 is found to be an excellent sensor for a biologically/physiologically very important transition metal ion (Cu(2+)) using only the two very different modes of measurements (absorption and emission); one case displayed intensity enhancement whereas in other case showed intensity depletion (quenching). A mechanistic investigation has been performed to explore the static nature of quenching process. The sensor has been found to be very effective in sensing Cu(2+) ion inside living cells also.