N4-dibenzosuberene substituted thiosemicarbazones based targetable fluorescent probe for multi-anion recognition

Two novel N4-suberene substituted thiosemicarbazone chemosensors (SATSC 1 and SATSC 2) designed and synthesised for the colorimetric and optical response towards anions were studied. Dimethylsulphoxide solution of SATSC 1-2 show bands in 350-400 nm region that are tuned for major π interactions in the heterocyclic system. Among the various anions only fluoride, acetate and cyanide exhibit good sensing responses. From the UV spectrum analysis, the emergence of a new red-shifted band with the colour change of solutions from yellow to dark yellow or orange due to the deprotonation is witnessed. Here, two processes occur mainly i.e., in the first step comes with the formation of a stable complex and a second step in which the sensor is deprotonated by the anions. These non-fluorescent sensors display fluorescent enhancement after binding with the F/AcO/CN ions. The fluorescent studies which are in good agreement with the observed changes in that of UV experiments. The stoichiometric ratio was calculated for all the receptors with anions and found it as in a 1:1 ratio. The sensor SATSC 2 shows a better binding affinity towards fluoride anion than SATSC 1. The binding mechanism and H-donating ability of the receptors are evaluated based on the observed fluorescence enhancement and H NMR titrations experiments with the fluoride. Constructed Logic gate behaviour over the reversibility experiments of the sensors SATSC 2 with the addition of fluoride and calcium ion. Graphic abstract: [Figure not available: see fulltext.] Synopsis This article reports two novel N4 suberene substituted thiosemicarbazone probes for the optical detection of some biologically and environmentally active anions like F-/AcO-/CN- ions. Studied the acidic –N-H proton triggered photo physical changes by UV, Luminescence and NMR spectroscopy. Logic operations were performed with binary inputs produced from reversibility study.