Studies on the acidity properties of Eu(III) complexes with α-amino acids by 13C NMR

The C-13 NMR spectra of Eu(III) complexes with alanine and histidine were investigated respectively. An interesting regularity of C-13 NMR shifts was revealed. The relationship between the structure of the obtained complexes and pH condition was discussed in detail. It was pointed out that the variations in 13C NMR shifts were resulted from the change of the complex structure. The possibility of coordination through the nitrogen in alpha-amino group under a weak acidic condition was also discussed. In addition, a calculation gave a further support to this view point.