Abstract/Summary

We herein report two salicyaldehyde-quinoxaline (HQS and HQSN) conjugates and a benzaldehyde-quinoxaline (QBN) conjugate to fabricate selective chemosensors for F− and Hg2+ in the micromolar range. This work demonstrates how sensing outcomes are affected by modulating proton acidity by introducing an electron donating group, −NEt2, in the probe backbone. Interestingly, the un-substituted probe HQS can selectively detect F−, whereas HQSN and QBN are selective for Hg2+. In order to gain insights into the mechanism of sensing, geometry optimizations have been carried out on QS(−1), QS(−1)⋅⋅⋅HF, QSN(−1) and QSN(−1)⋅⋅⋅HF and the experimental data are validated in terms of free energy and pKa values. Detailed DFT and TD-DFT analyses provide ample support towards the mechanism of sensing of the analytes.