Coumarine–imino–C2-glucosyl conjugate as receptor for Cu2+ in blood serum milieu, on silica gel sheet and in Hep G2 cells and the characterization of the species of recognition

• Water soluble and biologically benign coumarine–imino–glycoconjugate (L) is reported.
• L is selective for Cu2+ in aqueous HEPES buffer, blood serum and on silica gel.
• The minimum detection concentration of Cu2+ by L in HEPER buffer is 110 ± 16 nM.
• L enters into living cells and can be imaged by fluorescence spectroscopy.
• The dinuclear Cu(II) complex is studied by absorption, FTIR, P-XRD, ESI-MS and DFT.

A coumarine–imino–C2-glucosyl conjugate (L) was synthesized and characterized. The conjugate L is found to recognize Cu2+ in aqueous HEPES buffer by exhibiting a 95% fluorescence quenching in pH range 7–10 even in the presence of several biologically and ecologically relevant metal ions. Fluorescence on–off behavior has been clearly demonstrated on the basis of the binding variability of Cu2+ to L. The binding has been elicited through the changes observed in fluorescence, absorption, ESI-MS and 1H NMR titrations. All the other thirteen metal ions studied did not show any change in the fluorescence emission. These ions do not interfere with the recognition of Cu2+ by L. The structural features of [CuL]2 complex in both the isomeric forms were established by DFT computational calculations. The utility of L has been demonstrated by showing its sensitivity toward Cu2+ on a thin layer of silica gel. The L gives sensitive fluorescence signals for Cu2+ even in blood serum and exhibits appropriate fluorescence responses in living cells.

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