The M(H) curves are quite typical for Er III complexes with approximate C3 symmetry. The curves for all three states of compound 1 and for the two states of 2 are nearly identical and differ only in the level of the quasi-plateau reflected by the maximum magnetization value at 7 T: 14.4 N for 1, 15.1 N for 1UV, 14.7 N for 1vis and 4.9 N for 2 and 5.0 N for 2UV. The changes within the 11UV1vis sequence seem to be systematic and might be associated with the influence of the dtepy reversible photocyclization. The magnetic hysteresis could not be observed for any of the compounds even after irradiation.