Synthesis, structural and magnetic characterization of the metamagnet [Fe(C5Me5)2]DMe–DCNQI

The addition of a solution of decamethylferrocene, [Fe(Cp*)2], to a solution containing N,N′-dicyano-2,5-dimethyl-1,4-benzoquinonediimine, DMe–DCNQI, results in the formation of the electron-transfer salt [Fe(Cp*)2]DMe–DCNQI. A single crystal X-ray structure determination showed that this compound belongs to the triclinic space group P1̄, with a=8.6665(6) Å, b=9.5552(5) Å, c=9.8392(5) Å, α=101.421(5)°, β=112.523(5)°, γ=106.639(6)°, Z=1, R1=0.0536, wR2=0.1499. The solid state structure consists of an array of parallel alternating donors, [Fe(Cp*)2]radical dot+, and acceptors, DMe–DCNQIradical dot−, ⋯DADADA⋯ stacks along [111]. At high temperatures (T>20 K), the magnetic susceptibility obeys to the Curie–Weiss expression, with a θ value of 3.2 K, revealing the existence of dominant FM interactions. At low temperatures a metamagnetic behavior was observed for [Fe(Cp*)2]DMe–DCNQI, with TN=3.9 K and HC=5.5 kG at 1.7 K, resulting from a high magnetic anisotropy, due to the coexistence of strong FM DA intrachain interactions and weaker AFM (DD and AA) interchain interactions.