EPR studies of a cyano-bridged {Fe2IIINiII} coordination complex and its corresponding FeIII mononuclear building-block

High-field/frequency electron paramagnetic resonance measurements have been performed on a cyano-bridged trinuclear Fe2IIINiII complex and an analogous mononuclear FeIII building block. The mononuclear FeIII complex exhibits a low-spin configuration resulting from a strong-field coordination environment and can be modeled as an effective s = 1/2 Kramers ion that exhibits significant g-anisotropy: gz = 3.7, gy = 2.2 and gx = 1.92. The corresponding Fe2IIINiII complex possesses an S = 2 spin ground state as a result of ferromagnetic exchange that is mediated by the bridging cyano ligands. Simulations of frequency dependent EPR data establish that the Fe2IIINiII complex exhibits easy-axis type magnetoanisotropy, with best-fit simulation parameters of: S = 2, D = −2.09 cm−1, E = 0.08 cm−1, B40 = 2.3 × 10−3 cm−1, gz = 2.4, gy = gx = 1.95.

In this study we employ high-field/frequency single-crystal and powder EPR techniques to study a low-spin FeIII mononuclear building block which is subsequently used to synthesize a trinuclear Fe2IIINiII complex. Ferromagnetic exchange between the s = 1/2 FeIII monomers and the central NiII ion yields an interesting S = 2 system that exhibits easy-axis type magnetic anisotropy.Figure optionsDownload as PowerPoint slide