Imino–phenolic–azodye appended rhodamine as a primary fluorescence “off–on” chemosensor for tin (Sn4+) in solution and in RAW cells and the recognition of sulphide by [AR–Sn]

Abstract

A new azo-rhodamine based species, AR was developed to act as an ‘off–on’ reversible luminescent probe for Sn⁴⁺ detection. The chemosensing behavior of the AR has been demonstrated through fluorescence, absorption, visual fluorescence color changes, ESI MS and ¹H NMR titrations. This chemosensor AR shows a significant visible color change and displays a remarkable luminescent switch on (>2300 fold) in the presence of Sn⁴⁺ ions. The chemosensor can be used as a ‘naked eye’ sensor. The roles of the fluorophore–photochrome (azodye) dyad platform as well as the iminophenolic binding core in AR's selective recognition of tin have been demonstrated by studying appropriate control molecules. Importantly, AR can selectively recognize Sn⁴⁺ in organo-aqueous media in the presence of other cations. The biological applications of AR were evaluated in RAW cells and it was found to exhibit low cytotoxicity and good membrane permeability for the detection of Sn⁴⁺. The development of practically viable colorimetric test strips of the chemosensor AR to detect Sn⁴⁺ was also reported. It has been possible to build an INHIBIT logic gate for two binary inputs viz., Sn⁴⁺ and S²⁻ by monitoring the fluorescence emission band at 582 nm as output.