A dual functional colorimetric and fluorescence chemosensor based on benzo[f]fluorescein dye derivatives for copper ions and pH; kinetics and thermodynamic study

[Display omitted] •New derivatives of Xanthene dyes (BFFNH) was prepared and fully characterized.•The prepared compound showing high selectivity and sensitivity in micro-mole to Cu+2.•The BFFNH considered as a duel functional chemosensor to heavy metal and pH.•Thermodynamics and kinetics study of the coordinated sensor was investigated.•The application of BFFNH for monitoring of Cu2+ ions in water was studied. A new dual functional fluorescein-based colorimetric chemosensor 3′,6′-dihydroxy-2-(((2-hydroxynaphthalen-1-yl)methylene)amino)-6-methyl-4-(p-tolyl)spiro[benzo[f]isoindole-1,9′-xanthen]-3(2H)-one (BFFNH) derived from benzo[f]fluorescein was synthesized. Spectroscopy analysis confirmed the structures of the prepared compounds. BFFNH shows the colorimetric selectivity and sensitivity towards the aqueous solution of Cu2+ ions with a detection limit in the micromolar range (0.5μM). The applications of BFFNH was extended for the detection of Cu2+ ions in real water samples (tab and synthetic water) with a high recovery%. Also, BFFNH appeared to be highly sensitive with a quick response as fluorescence probe to alkaline pH hence its pKa value calculated as 7.91. Thermodynamic parameters ΔS, ΔH and ΔG investigated at four temperatures (15, 20, 25 and 30°C). Kinetic study showed a first-order reaction with respect to the ligand. Also, the association constant (Ka) of BFFNH which binding with Cu2+ ions based on 1:1 stoichiometry was calculated.