Quinazoline copper(II) ensemble as turn-on fluorescence sensor for cysteine and chemodosimeter for NO

A fluorescent quinazoline based chemosensor QHYN had been designed and synthesized. It exhibits high sensitivity and selectivity towards Cu2+ over other metal ions in DMSO:H2O (1:9, v/v) at pH = 7.4 [HEPES buffer] by fluorescence quenching. Addition of nitric oxide to a solution of this QHYN·Cu(II) restores the fluorescence. This is attributed to the reduction of the Cu(II) centre by nitric oxide to diamagnetic Cu(I). The fluorescence response of QHYN·Cu(II) to NO is direct and specific, which is a significant improvement over commercially available small molecule-based chemodosimeter probe that are capable of detecting NO. The QHYN·Cu(II) also acts as an efficient “off–on” fluorescent sensor for cysteine with high sensitivity.