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

AbstractFour quinoline based non‐heme tetradendate ligands viz. N,N′‐di(quinolin‐8‐yl)ethane‐1,2‐diamine (BQENH2) 1, N,N′‐di(quinolin‐8‐yl)propane‐1,3‐diamine 2 (BQPNH2), N,N′‐di(quinolin‐8‐yl)butane‐1,4‐diamine (BQEBNH2) 3 and N,N′‐di(quinolin‐8‐yl)hexane‐1,6‐diamine (BQEHNH2) 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, 1H‐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.