Perylene Diimide-Based Pseudo-Crown Ether I: Supramolecular Aggregates for Sensing of Pb2+ and Diethanolamine

A pseudo-Crown ether (open chained podand) containing two rigid and bulky perylene diimide units as terminal end-group (diPDI 2) has been synthesized. The diPDI 2 selectively binds with Pb2+ ions to form 2 : 1 sandwich type complex (Job's plot, NMR and SPECFIT) in solution. The complexation led to significant changes in fluorescence and absorbance; in NMR chemical shifts (Delta delta=0.5-0.6 ppm) and in size of the aggregates (DLS, AFM). We further demonstrated formation of diPDI 2-Pb2+ host-guest supramolecular complex using Cyclic voltammetry (CV), powder X-ray diffraction, thermogravimetry (TGA), Infrared, Raman spectroscopies. The Hill coefficient (n(H)) value of >3.7 indicates cooperativity in Pb2+ binding process at high concentrations. We also demonstrated utility of diPDI 2+Pb2+ complex in a 'turn-on' sensing of biological relevant amines such as spermine and diethanolamine (DEA) using displacement approach. The dissociation of diPDI 2+Pb2+ complex with these amines via sequestration of Pb2+ results in restoration of optical and NMR chemical shift signals. The reversibility of diPDI 2+Pb2+ complex with DEA offers fabrication of IMPLICATION logic gate.

Automated summary

This article describes the synthesis of a pseudo-crown ether that selectively binds with Pb2+ ions in solution, leading to significant changes in various properties and potential applications in the biological field. The complexation was characterized and demonstrated using multiple techniques, showing a potential 'turn-on' sensing approach for amines through displacement method.