A multifunctional colorimetric chemosensor for cyanide and copper(II) ions

•A new and highly selective colorimetric sensor for CN− and Cu2+ was developed.•Test kit provided a convenient and reliable detection of CN− in practical application.•Sensing mechanisms for CN− and Cu2+ was supported by theoretical calculations. We designed and synthesized a new asymmetric chemosensor 1 based on the combination of salicylaldehyde moiety and 2-amino-3-(((E)-(8-hydroxy-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-9yl)methylene)amino)maleonitrile followed by the condensation reaction of julolidine and 2,3-diaminomaleonitrile. The sensor 1 exhibited definite color changes from violet to pale yellow for CN− and Cu2+ separately in different solvent systems. The phenomena possibly originated from blue shift generated by the intramolecular charge transfer (ICT) transition. The complex formations were proposed to be in 1:1 ratio, based on Job plot, 1H NMR titration and ESI-mass spectrometry analysis. Furthermore, the multifunctional colorimetric sensing ability of 1 was theoretically explained by DFT and TDDFT calculations.