Pyrrolo-benzodiazepine fluorophore for trace amount detection of Cu2+ and application in living cells

Abstract In general, paramagnetic ions serve as fluorescence quencher. Very few fluorogens are known who could enhance emission on binding with paramagnetic transition metal ions. In this work, a novel (3-methoxy-7-pyridin-2-yl-5, 6, 8, 13-tetrahydro-7H-8, 13a-diaza-benzo [f]naphtho [2,1-a]azulen-14-yl)-acetic acid methyl ester (HPBD) is characterized by spectroscopic techniques who selectively senses Cu2+ ions with the ‘turn-on’ fluorescence enhancement at 463 ​nm over 25 metal ions. Limit of detection is as low as 35.58 ​nM (EPA recommended tolerance limit, 20 ​μM) in buffered (HEPES, pH, 7.4) acetonitrile (MeCN)/H2O (v/v, 19:1) medium. The 1:1 composition of [Cu-PBD]+ complex is supported by fluorometric Job's plot, mass spectra and Bensei-Hildebrand plot (association constant Ka ​= ​ 5.2 × 10 4 M − 1 ). It is further studied to monitor Cu2+ ions in Hep G2 cells by fluorescence microscope.