Octahedral-Tetrahedral Systems [Co( dppm O, O)3]2+[CoX4]2- Showing Slow Magnetic Relaxation with Two Relaxation Modes.

Three compounds with octahedral-tetrahedral Co(II) moieties of [Co( dppm O, O)3][CoX4] type, where X = SCN (1), Cl (2), or I (4) have been synthesized and characterized by the X-ray structure analysis (1 and 4), and spectroscopic methods. The dc magnetic measurements show high magnetic anisotropy for octahedral centers whereas tetrahedral sites possess moderate D values. These results are confirmed by the ab initio calculations. The ac susceptibility data reveals a slow magnetic relaxation for 2 and 4, similar to that of the X = Br analogue (3), whereas 1 displays no ac-absorption signal. There are two relaxation channels; the slower for 2 (4) possesses a relaxation time as long as τLF= 178 (588) ms at T = 1.9 K and Bdc = 0.7 T. Also, the half-Zn analogue, [Co( dppm O, O)3][ZnI4], shows slow magnetic relaxation with two relaxation channels conditioned by the cationic unit [Co( dppm O, O)3]2+.