Phenothiazine-pyridyl chalcone: an easily accessible colorimetric and fluorimetric ‘on–off’ dual sensing probe for Cu2+

Phenothiazine-pyridyl chalcone, a new internal charge transfer (ICT) probe, has been designed that allows naked eye detection and a reversible, ratiometric ‘on–off’ sensing capability for biologically and environmentally significant Cu2+ in CH3OH–H2O (4:1 v/v) under buffered conditions. The association constants determined using spectrophotometric and the fluorimetric techniques follow the order Cu2+ > Ni2+ > Co2+ > Zn2+ > Cd2+ > Mg2+ ≈ Ba2+ ≈ Ca2+ ≈ K+≈ Na+ ≈ Li+.