Mononuclear High-spin Octahedral Cobalt(II) Complex with Positive Axial Magnetic Anisotropy: Synthesis, Crystal Structure, and DFT Studies

This article outlines the magnetic features of a new six-coordinate high-spin cobalt(II) complex cis-[Co-II(tmphen)(2)(NCS)(2)] (1) achieved via the reactions of cobalt(II) thiocyanate with 3,4,7,8-tetramethyl-1,10-phenanthroline. The complex 1 was thoroughly characterized by different analytical and spectroscopic techniques and further confirmed by single X-ray crystal diffraction pattern. Complex 1 is a neutral molecule and adopt highly distorted six-coordinate CoN6 octahedral coordination sphere surrounded by two thiocyanate N atoms in cis locations and the equatorial plane is occupied by two imine N atoms from the two tmphen ligand while the remaining two imine N atoms reside in the axial positions. Magnetic susceptibility data of complex 1 revealed that the chi T-M values decrease significantly to a value of 1.49 cm(3)center dot K center dot mol(-1) at 2.0 K on decreasing temperatures below 100 K, mainly ascribed to the significant spin-orbit coupling (SOC) of six-coordinate Co-II ions. Furthermore, a field-dependence measurement was performed at 2 K, which shows a positive curvature up to 27 kOe, while it becomes linear up to 2.01 N mu(B), which authenticated the fact that only the lowest Kramers doublet of ground state is appreciably populated.