An acyclic, dansyl based colorimetric and fluorescent chemosensor for Hg(II) via twisted intramolecular charge transfer (TICT)

An efficient fluorescent chemosensor for Hg(2+) ion, based on 5-(dimethylamino)-N-(2-mercaptophenyl)naphthalene-1-sulfonamide, has been developed. It exhibits Hg(2+)-selective on-off fluorescence quenching behavior via twisted intramolecular charge transfer (TICT) mechanism, which is rationalized by time dependent density functional theory (TD-DFT) calculations. The system exhibits visible color change from colorless to gray upon Hg(2+) binding with very high selectivity and sensitivity (as low as 5.0×10(-10)molL(-1)) over other metal ions such as K(+), Na(+), Ag(+), Mn(2+), Ca(2+), Ba(2+), Fe(2+), Zn(2+), Pb(2+), Cu(2+), Sn(2+), Cd(2+), Ni(2+) and Co(2+). The present sensing system is also successfully applied for the detection of Hg(2+) ion in real samples.