Rare earth complexation with 1,3,5-trideoxy-1,3,5-tris(2-hydroxybenzyl)amino-cis-inositol

The protonation constants of 1,3,5-trideoxy-1,3,5-tris(2-hydroxyl-benzyl)amino-cis-inositol (thci) in I = 1 M (NaClO4) were determined to be: pKa1 5.96 ± 0.03, pKa2 7.21 ± 0.01, pKa3 8.32 ± 0.07, pKa4 8.95 ± 0.06. The solvent extraction studies were consistent with the formation of the Ln(thci)3+ and Ln(thci)23+ complexes. The log of the stability constants (log β1 and log β2) at 25 °C in 1 M (NaClO4) at pH 4 for formation of these complexes are reported. Laser luminescence measurements of the 7F0–5D0 transition of Eu(III) complexed by thci indicated two species. The shifts in the peaks relative to that of Eu(aq)3+ were comparable to the values reported for other complexes of Eu(III) with organic ligands, but the intensities were greater. Luminescence lifetime measurements of the fluorescence spectra indicated that the Eu(thci)23+ complex has 5 inner sphere water molecules bound to the Eu(III) cation at pH 6.71–8.52. This was consistent with bidentate chelation of Eu(III) with each thci molecule. gaussian view energy calculations indicated bonding for M(III) to the amino and hydroxyl groups of the cyclohexanetriol and (2-hydroxybenzyl)amino moieties in the Ln(thci)3+ complex.

Graphical abstractRare earth complexation with 1,3,5,-trideoxy-1,3,5-tris(2-hydroxybenzyl)amino-cis-inositol and the lanthanide metals Pm(III), Eu(III), and Y(III) were studied. The protonation constants and the stability constants log β1 and log β2 at pH 4.00, l were determined in 1.00 M NaClO4. Laser luminescence measurements of the 7F0–5D0 transition indicated two species.Figure optionsDownload full-size imageDownload as PowerPoint slide