1-(2-Naphthyl)benzimidazolium based tripod for fluorescence enhancement based recognition of surfactants in water

Abstract

1-(2-Naphthyl)benzimidazolium based fluorogenic tripod TRI-BINAP-1 exhibits highly selective and sensitive recognition of surfactants SDBS and SDS in water amongst a series of inorganic and organic anions. The titration studies, Job's plot, ¹H NMR studies and HRMS conspicuously reveal the co-operative participation of the three arms of the tripod for encapsulation of SDS or SDBS in the tripod cavity. The long chain carboxylates exhibit change in fluorescence at much higher concentrations and Job's plot shows the non-cooperative binding of the three arms of the tripod to form a 1 : 3 (tripod : carboxylate) stoichiometric complex. The lowest detection limit for SDBS and SDS by fluorescence is 0.25 μM. The reduced flipping of the naphthyl rings on complexation of TRI-BINAP-1 with SDBS or SDS decreases thermal deactivation processes and leads to enhanced fluorescence.