A multifaceted ferrocene-benzobisimidazole derivative: fluorogenic probe for Pb(2+) and Zn(2+) cations and unconventional fluorescence behaviour towards Cu(2+) metal cations.

The ferrocene-benzobisimidazole derivative shows high affinity for Pb(2+) and Zn(2+) metal cations over a range of other metal cations examined. In the presence of Pb(2+) the emission spectrum is red-shifted by 13 nm with an important chelation-enhanced fluorescence effect (CHEF) CHEF = 55. The presence of Zn(2+) cations also induced a perturbation of the emission spectrum although to a lesser extent than that found for Pb(2+) cations (CHEF = 37). Upon complexation with Cu(2+) cations, not only is the emission band red-shifted (Deltalambda = 67 nm) with a noticeable CHEF = 20, but also the maximum of such fluorescence emission exhibits a concomitant shift towards higher wavelengths when the excitation wavelength is gradually shifted to the red-edge of the absorption band (red-edge effect).