The solution structures of diamagnetic lanthanide (III) complexes of DTPA-B
IN (Ln = La, Y, Lu, Sc) have been investigated by H-1 NMR, C-13 NMR and 2D
NMR. For each complex, two or more species of asymmetric conformations with
little distinction were identified at room temperature. And their solution
structures vary with the radius of the central metals. NMR spectra support
the hypothesis that Sc3+ with smaller radius formed an eight-coordinated s
tructure with DTPA-BIN, La3+ with larger radius formed nine- or ten-coordin
ated structures with DTPA-BIN, and Y (DTPA-BIN) and Lu (DTPA-BIN) had nine-
coordinated solution structures. The solution structure of Gd (DTPA-BIN) wa
s obtained from the similarity of radius between Gd3+ and Y3+, which is a n
ine-coordinated structure formed by three nitrogens, three acetate oxygens,
two acetyl oxygens, one water molecule and a gadolinium(III) cation.