Acyclic polyorganochalcogenoethers and their functional activities: Synthesis of sterically encumbered hexakis(alkylchalcogenomethyl)benzenes [(RECH2)6C6] [E=S or Se] and their potential as selective ionophores for Hg2+ ions

An efficient synthesis of hexakis(alkylthio/selenomethyl)benzenes [(RSCH2)6C6 and (RSeCH2)6C6] (1-14) (where, R= nPr, iPr, nBu, iBu, sBu, tBu, nPent, iPent, and 2-Methyl-1-butyl) by the reaction of hexakis(bromomethyl)benzene with alkylthio or alkylseleno (RS-/RSe-) anions are demonstrated. They have been characterized by physicochemical and spectroscopic methods including single crystal X-ray crystallography. The balances between multiple [C(sp3)-H…S] or [C(sp3)-H…Se] intramolecular interactions in these species appear to decide their stability. Preliminary spectroscopic (UV-vis. and fluorescence) data on the behavior of alkylchalcogeno substituted hexa-benzenes in solution revealed their potential as ion-sensing species and function as highly selective ionophores for Ag+ and Hg2+ ions recognition. In situ, (Hg-S) and (Hg-Se) bond formation on interaction with the chosen hexa-species (2 and 10) and Hg2+ cation revealed a unique ‘turn-off’ or ‘turn-on’ emissive behavior and these function act as reporting fluorescent tool for Hg2+ quantification without use of any external fluorophore. The present study describes an efficient and simple route for the synthesis of sterically encumbered poly-alkylthio/seleno benzenes in high purity and good yields.