A chiral probe for the detection of Cu(ii) by UV, CD and emission spectroscopies

Abstract

The synthesis and characterization of the new chiral ligand 2, based on a BINOL–tren (tren = tris(2-aminoethyl)amine) conjugate, in enantiomerically pure form, are reported. UV-Vis spectrophotometric and spectrofluorimetric studies at variable pH show that the incorporation of a phenolic functionality in close proximity to the polyamino fragment of the molecule causes a dramatic variation of the acid–base and coordination properties of the molecule; the major role of this functionality in determining the selectivity observed in the complexation of Cu²⁺, when compared with Zn²⁺ and Ni²⁺, at pH = 5 in aqueous MeOH, has been clarified, also by comparison with the spectroscopic and coordination properties of model compound 3, bearing protected OMe functionalities. The peculiar absorbance, emission and chiroptical properties of the binaphthyl fragment incorporated in compound 2 can be used for the selective detection of Cu²⁺ using three different and potentially orthogonal techniques, namely UV, CD and fluorescence spectroscopies.