Triimidosulfonates as Acute Bite-Angle Chelates: Slow Relaxation of the Magnetization in Zero Field and Hysteresis Loop of a CoII Complex

Starting from a polyimido sulfonate the four-coordinate, N,N-chelated Co-II complex [Co{(NtBu)(3)SMe}(2)] (1) was synthesized, and its molecular structure was elucidated by single-crystal X-ray structural analysis. The acute N-Co-N bite angle imposed by the N,N-chelating ligand (NtBu)(3)SMe- leads to pronounced C-2v distortion of the tetrahedral coordination environment and thus to high anisotropy of the Co-II ion (D approximate to-58cm(-1)), favorable for single-molecule-magnet (SMM) properties. Magnetic measurements revealed a high barrier to spin reversal (U-eff=75cm(-1)) that gives rise to the observation of slow relaxation of the magnetization in zero field and a hysteresis loop at 2K for this unique complex.