Triazole appended mono and 1,1′ di-substituted ferrocene-naphthalene conjugates: Highly selective and sensitive multi-responsive probes for Hg(II)

A couple of triazole-tethered simple colorimetric, electrochemical and fluorescent chemosensors, based on ferrocene-naphthalene conjugates, C24H21ON3Fe (1) and C38H32O2N6Fe (2), have been designed and synthesized. The interactions of 1 and 2 with several metal ions have been investigated systematically which show their strong binding affinity towards Hg2+ ion selectively. The binding incident of both the receptors can be established either from a striking shift in redox potential (1: Delta E-1/2 = 76 mV and 2: Delta E-1/2 =43 mV for Hg2+) or from a highly visual output response (colorimetric) for Hg2+ cation. The limit of detection with Hg2+ cation was found as low as 2.6 parts per billion (ppb) and 4.5 ppb for 1 and 2 respectively, which is well below of the maximum level of Hg2+ cation in drinking water defined by EPA guidelines. Furthermore, the sensors exhibit good sensitivity and selectivity for Hg2+ cation on paper-made test kits and on supported solid silica in aqueous environment. The probable binding modes of these receptors with Hg2+ have also been suggested on the basis of the H-1 NMR titration, ESI-MS and computational (DFT) studies along with electrochemical and spectro-photochemical data. (C) 2016 Elsevier B.V. All rights reserved.