Lipophilic Ligands Derived from 1,3,5-Triamino-1,3,5-trideoxy-cis-inositol (Taci) for Trivalent Lanthanide Complexation in Aqueous and Organic Solutions

摘要

New lipophilic ligands derived from 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci), namely 1,3,5-trideoxy-1,3,5-tris-(ethylamino)-cis-inositol (L~1), 1,3,5-tris (butylamino)-1,3,5-trideoxy-cis-insitol (L~2), 1,3,5-trideoxy-1,3,5-tris (hexylamino)-cis-inositol (L~3) have been synthesized by reductive amination of taci. Their complexing properties towards trivalent lanthanide cations, together with those of 1,3,5-tris (benzylamino)-1,3,5-trideoxy-cis-inositol (L~4), have been investigated in solution using mass spectrometry. NMR spectroscopy and potentiometry. It has been shown that each ligand forms trinuclear complexes with the composition [Ln_2(LH_(-3))_2]~(3+). The stability constants (log beta_(32-6)) of these complexes have been calculated for Nd~(3+), Eu~(3+), and in some cases for Lu~(3+). The affinity for the lanthanide cations follows the sequence Lu~(3+) > Eu~(3+) > Nd~(3+), for all the ligands. Theis sequence follows the well-known electrostatic trend. The stability of the complex depends on the conjugate effects of the steric hindrance of the substituents and the basicity of the ligands: L~1 approx = L~2 taci, in water, and L~3 < L~2 L~4, in water/methanol. Among the ligands studied in this work, L~4 appears to be the most effective complexing agent for the lanthanide cations in water/methanol under slightly acidic conditions.