Dual colorimetric and fluorescent chemosensor of Fe3+ and Cu2+ based on 2,5-bis[(4-carboxylic-piperidylamino)thiophenyl]-croconine

A croconium dye, 2,5-bis[(4-carboxylic-piperidylamino)thiophenyl]-croconine (BCTC) based dual signaling probe was found to exhibit colorimetric and fluorescent properties on selective binding towards Fe3+ and Cu2+ in ethanol/water (4:1, v/v) solution, respectively. The binding constants were determined to be 2.12×104 M−1 and 8.58×104 M−1 for Fe3+ and Cu2+, respectively. Most importantly, the 1:1 stoichiometry of the host-guest complexation was confirmed by Job's method. This result was further confirmed by 1H NMR analysis. Meanwhile, the selectivity experiments revealed that the colorimetric and fluorescent sensor were specific for Fe3+ and Cu2+ even with interference by high concentrations of other metal ions. Moreover, the sensing abilities of the receptor toward Fe3+ and Cu2+ were also investigated by electrochemical technique. The present results indicated that the BCTC chemosensor could be adopted as a selective, sensitive and reversible colorimetric and fluorescent sensor for Fe3+ and Cu2+.