Orthogonal sample design scheme for two-dimensional synchronous spectroscopy: Application in probing lanthanide ions interactions with organic ligands in solution mixtures

Weak interactions between lanthanide (III) ions and organic ligands in solution mixtures are studied by using two-dimensional synchronous spectroscopy together with “Orthogonal Sample Design” (OSD) scheme that can effectively remove the interfering cross peaks in 2D synchronous spectrum. Two representative chemical systems are investigated and discussed here: (1) PrCl3/butanone in ethanol solution, where weak coordinative interaction between Pr3+ and carbonyl group from butanone is characterized by using 2D UV/IR heterogeneous spectroscopy; and (2) NdCl3/5-sulfosalicylic acid in aqueous solution, where the interaction between Nd3+/5-sulfosalicylic acid is investigated by using 2D UV spectra. The cross peaks occurred in the 2D spectra confirm the weak interactions between lanthanide (III) ions and corresponding molecules where no observable variation occurs in conventional 1D spectra.