A novel pyromellitic diimide derivative: Synthesis, gelation and spontaneous colorimetric sensing of dihydroxybenzene isomers

We report on the synthesis and self-assembly of a new hydrazide derivative N′, N′-bis[4-octadecyloxybenzamido]pyromellitic diimide (compound 1) which formed gels in several apolar organic solvents such as benzene and 1, 2-dichloroethane. 1H NMR, and FT-IR spectroscopy studies confirmed that the intermolecular hydrogen bonding and van der Waals interactions were major driving forces for the formation of self-assembling gels. The gelator can form noncovalent interactions with dihydroxybenzenes, exhibiting different colors when it complexes with different positional isomers, and thus can be used to sense the positional isomers of dihydroxybenzenes by the naked eyes. This sensing property was further investigated by UV/Vis, 1H NMR, and 1H NMR NOESY spectroscopy which revealed that the charge–transfer interaction between hydroxyl groups of the dihydroxybenzene isomers (donor) and compound 1 (acceptor) accounted for this property.