Mössbauer spectra of Eu(III) and Gd(III) complexes of phosphine oxides with chelating perchlorate

The reaction of Ln(ClO4)3· nH2O with triphenylphosphine oxide (TPPO) in methanol has led to the formation of [Ln(ClO4)2(tppo)4]ClO4·MeOH (Ln = Nd, Eu, Gd, Dy, Yb), in which the perchlorate anion acts as a symmetric bidentate. The emission spectra of Eu(III)-TPPO complexes, showing enhancement in the intensity due to the phenyl group, indicate an isotropic electron distribution for the nitrato complex [Eu(NO3)3(tppo)2(EtOH)]. 151Eu and 155Gd Mössbauer spectra of the TPPO complexes also lead to the same conclusion.