Results in Chemistry (Jan 2022)
Squaramide-naphthalimide conjugates – Exploiting self-aggregation effects in acetate recognition
Abstract
The synthesis of three squaramide-containing bis-naphthalimide conjugates (1–3) are reported where the structures differ by the length of the carbon chain between the squaramide core and the 1,8-naphthalimide fluorophores. All compounds displayed weak fluorescence properties and self-aggregation as studied by UV/Vis, 1H NMR spectroscopy and Scanning Electron Microscopy (SEM), however it was shown that aggregation can be disrupted by increased temperature. Anion binding experiments displayed colourimetric and spectroscopic modulations in response to a variety of anions where more basic anions resulted in receptor deprotonation. However, selectivity was observed in the case of H-bonding to OAc- with binding measured by 1H NMR titration experiments. No fluorometric changes were observed for any of the anions tested and we propose that the squaramide is capable of disrupting eximer formation resulting in a reduction of emission from these systems.
