Slow magnetic relaxation in two octahedral cobalt(II) complexes with positive axial anisotropy.

Two mononuclear Co(II) complexes [Co(L) 4 (NO 3 ) 2 ] (L = 3-phenylpyrazole for 1 and 4-methylpyridine for 2 ) featuring distorted octahedral geometry were prepared and structurally characterized by X-ray crystallographic analyses. Direct-current magnetic and high-frequency/field electron paramagnetic resonance measurements reveal that both complexes have the large and positive D values with the non-negligible transverse anisotropy ( E ). Slow magnetic relaxation effects were observed under the applied direct-current field in 1 and 2 by dynamic alternative-current magnetic susceptibility measurements, which provide two interesting examples of six-coordinate Co(II)-based single ion magnets constructed by nitrate groups and nitrogen heterocyclic compounds in mono-dentate coordination modes. [ABSTRACT FROM AUTHOR]