Magnetic Properties of a New Er(III) Macrobicyclic Complex Studied by EPR

The macrobicyclic ligands of a Schiff base form complexes with various lanthanide metal cations, where the lanthanide ion can be coordinated in the mono- or binuclear systems. As a result of the Schiff-base condensation, a new erbium cryptate complex has been synthesized and investigated by electron paramagnetic resonance EPR technique. The measurements in the 3.9–300 K temperature range confirmed the presence of the 1:1 macrobicyclic Schiff base–Er³⁺ complex. Computer simulations of the registered EPR spectra have revealed the existence of low-symmetry crystal field at the Er(III) site. The complicated EPR spectra of Er(III) complex with an effective spin S = 1/2 in low magnetic fields (<200 mT) were observed only below 60 K. At 5 K the anisotropic g-factors and the integrated intensity reached local maximum values. In the 5–13 K temperature range the line width and g-factors remained constant, while the integrated intensity strongly decreased with increasing temperature. Above 13 K a strong increase of g _y -factor and ΔB _y line width was observed. The observed peak in integrated intensity indicates that the EPR signal is produced by the excited state that lies 6.3 K above the nonmagnetic ground state. Authors' address: Sławomir M. Kaczmarek, Institute of Physics, Szczecin University of Technology, Al. Piastów 48, 70-310 Szczecin, Poland