Adenine-linked naphthalimide: A case of selective colorimetric as well as fluorometric sensing of F- and anion-activated moisture detection in organic solvents and CO2-sensing.

Abstract

Compounds 1, 2 and 3 with a common strategy of variation of substituent at the 4-position of naphthalimide have been designed and synthesized. Of the three structures, compound 1 has been established as F- sensor in CH3CN involving a color change from colorless to pink. The pink color is discharged in the presence of water or any polar protic solvent. By comparison, while compound 3 did not show any response towards anions, compound 2 under identical conditions exhibited color change from light yellow to pink in presence of several basic anions such as F-, AcO- and H2PO4-. This emphasizes the importance on structural tuning in establishing a new effective sensor for a particular anion. F--induced deprotonation of 1 and its reprotonation with water has been employed as the working principle to detect the moisture content in various organic solvents. In addition, F--activated CO2 sensing via color and fluorescence changes have been demonstrated using chemosensor 1. Compound 1 and F- coated paper exhibit color change on heating and cooling. Writing on this 1.F- coated paper using AcO- ion as ink and its appearance/disappearance on heating/cooling has been possible successfully.