A novel julolidine-based terpyridine derivative as a hydrogen bonding-induced fluorescence smart sensor for detecting methanol impurities in biodiesel

Abstract

Aiming to develop a novel fluorescent detection probe for methanol content in biodiesel, a julolidine fragment has been assembled into a terpyridine group to obtain an augmented electronic donor–π–acceptor (D–π–A) compound (A1), and in addition, the tetraphenylethylene-based terpyridine derivative (A2) was synthesized for comparison to research the photoelectric properties of A1. Molecule A1 exhibited solvatofluorochromism properties that other reported terpyridine derivatives do not possess. Furthermore, methanol might form a complex with nitrogen atoms in the julolidine part in compound A1 to disrupt the intramolecular charge transfer (ICT) process, and quench the fluorescence properties of the system. Therefore, compound A1 can serve as an “on–off” fluorescent sensor for the detection of methanol impurities in commercial biodiesel. Finally, interference research indicated that the presence of afterproducts and catalysts, such as glycerol, acid and alkali, causes no interference in methanol detection by sensor A1.