This value is close to those derived from the experimental magnetic data and points out the importance of balancing the active space. Finally, similar calculations were done for molecular structures derived from X-ray data acquired at higher temperatures to investigate how temperature-induced structural changes (Figure ) influence the properties. Again, the results are summarized for the CASSCF/QD-NEVPT2 method in Figure for the largest active space CAS (9e,12o). Obviously, the ( 4 ) -( 6 ) energy gap decreases with increasing temperature of the crystal data acquisition, which also reflects an increase of the D-parameter from 7.85 cm -1 to 10.08 cm -1 .