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 solut ion containing N,N ' -dicyano-2,5-dimethyl-1,4-benzoquinonediimine, DMe-DCN QI, results in the formation of the electron-transfer salt [Fc(Cp*)2]DMe-DC NQI. A single crystal X-ray structure determination showed that this compou nd belongs to the triclinic space group P (I) over bar with a = 8.6665(6) A ngstrom, b = 9.5552(5) Angstrom, c = 9.8392(5) Angstrom, alpha = 101.421(5) degrees, beta = 112.523(5)degrees, gamma = 106.639(6)degrees, Z = 1, R-1 = 0.0536, wR(2) = 0.1499. The solid state structure consists of an array of p arallel alternating donors, [Fe(Cp*)(2)](.+), and acceptors, DMe-DCNQI(.-), ...DADADA... stacks along [111]. At high temperatures (T > 20 K), the magn etic susceptibility obeys to the Curie-Weiss expression, with a theta value of 3.2 K, revealing the existence of dominant FM interactions. At low temp eratures a metamagnetic behavior was observed for [Fe(Cp*)(2)]DMe-DCNQI, wi th T-N = 3.9 K and H-C = 5.5 kG at 1.7 K, resulting from a high magnetic an isotropy, due to the coexistence of strong FM DA intrachain interactions an d weaker AFM (DD and AA) interchain interactions. (C) 2001 Elsevier Science B.V. All rights reserved.