Chemoselective detection of 2,4,6-trinitrophenol by ground state adduct formation via protonation of quinoline moiety of non-heme ligands with structural evidence

Abstract

Four quinoline based non-heme tetradendate ligands viz. N,N'-di(quinolin-8-yl)ethane-1,2-diamine (BQENH sub(2)) 1 , N,N'-di(quinolin-8-yl)propane-1,3-diamine 2 (BQPNH sub(2)), N,N'-di(quinolin-8-yl)butane-1,4-diamine (BQEBNH sub(2)) 3 and N,N'-di(quinolin-8-yl)hexane-1,6-diamine (BQEHNH sub(2)) 4 are structurally characterized and used in selective detection of 2,4,6-trinitrophenol (TNP) with high quenching constants. The plausible reaction mechanism involves ground state protonation of quinoline nitrogen atoms in compounds 1-4 by TNP with formation of picrate adducts (1 a -4 a ). The protonation of 1-4 is confirmed by infrared, sup(1) H-NMR spectroscopies, powder XRD and the single crystal structure analysis of 1 a and 4 a . Crystal structures further infer that after protonation, 1 a and 4 a are stabilized by intramolecular hydrogen bonding.