A new pyridine-dicarbohydrazide-based turn-off fluorescent and colorimetric chemosensor for selective recognition of Cu2+

Abstract

A novel indole-containing 2,6-pyridinedicarbohydrazide P3 was easily synthesized and well-characterized employing NMR, ESI+-MS, FT-IR, and elemental analyses. The synthesized compound was examined as an efficient turn-off fluorescent and colorimetric cation receptor. The P3 receptor exhibits a remarkable rapid color change from colorless to brown in the presence of the Cu2+ cation. P3 displayed selective fluorescence quenching and a UV-vis redshift only in the presence of Cu2+ ion. Job’s plot, NMR titration, and ESI+-MS data were used to determine the complex's 1:2 stoichiometry between P3 and Cu2+. Fluorescence titration was used to calculate the association constant (Ka) as (2.9–3.5) ×1011 M− 2 and LOD as \(\tilde\) 4.2 ×10−9 M. P3-based test strips were developed, which might be used as a simple and effective Cu2+ test kit. This design, which incorporates a functional group on the upper rim of the 2,6-pyridinedicarbohydrazide platform, is expected to provide another avenue for the development of chemosensors.