3-(2-Hydroxyphenyl)imidazo[5, 1-a]isoquinoline as Cu(II) sensor, its Cu(II) complex for selective detection of CN- ion and biological compatibility

The heterocyclic probe 3-(2-hydroxyphenyl)imidazo[5, 1-a]isoquinoline (LH) has exhibited specific recognition of Cu2+ ion by forming a complex of formula [Cu(L)(2)], which in turn showed recognition for CN- ions in CH3CN/aqueous HEPES-buffer solution (5 mM, pH = 7.4, 6:4, v/v). The selective colorimetric and fluorescence response of LH towards Cu2+ was achieved over other competing metal ions. Change of color from colorless to yellowish green upon incremental addition of Cu2+& nbsp;into LH solution can be easily observed with naked-eye. Emission intensity of LH was quenched in presence of Cu2+ ion due to chelation enhanced quenching (CHEQ) process. From Job's plot and mass spectral analysis the binding stoichiometry was found to 2:1 between LH and Cu2+. Binding of the probe LH with Cu2+& nbsp;ion can be reversed by sequestering Cu2+& nbsp;ion using Na(2)EDTA solutions. Red shift in UV-visible spectrum upon addition of Cu2+& nbsp;ion into LH solution was a consequence of decrease in HOMO-LUMO energy gap. From life time decay curve the average fluorescence life time (r) was found to be 3.8 ns for free LH whereas in presence of Cu2+& nbsp;r decreased to 2.4 ns. In addition, so formed [Cu(L)(2)] complex was able to detect cyanide ion over other anions through removal of copper from the complex, as insoluble [CuCN](x). Limit of detection of LH for Cu2+ and [Cu(L)(2)] for CN- were found to be 0.45 mu M and 0.30 mu M respectively. Detection of Cu2+& nbsp;and CN- were also performed in environmental real water samples. Based on the cytotoxic analysis, 5 mu M of LH was selected for determining its fluorescence attributes in cellular imaging in MDA-MB-231 and HDF cells. The cell images showed that intracellular Cu2+& nbsp;and CN- can be detected using LH and [Cu(L)(2)] complex respectively.

Automated summary

In this study, a heterocyclic probe LH was designed for specific recognition of Cu2+ ion and CN- ion. LH showed selective colorimetric response towards Cu2+ and recognition for CN- was achieved through formation of a specific complex. The results demonstrated the potential applications of LH and [Cu(L)(2)] complex in environmental water analysis and cellular imaging.