Magnetic behavior and crystal structure of [Fe(cyclam)(NCS)(2)](TCNQ)2: Anunusual one-dimensional (TCNQ)(2)(-) radical-ion system

The compound [Fe(cyclam)(NCS)(2)](TCNQ)(2), where cyclam is 1,4,8,11 -tetra azacyclotetradecane and TCNQ is a partially reduced 7,7,8,8-tetracyanoquino dimethane fragment, has been obtained from the corresponding thiocyanate by metathesis reaction. The compound crystallizes in the triclinic system, sp ace group P (1) over bar, a = 7.832(3) Angstrom, b = 8.008(2) Angstrom, c = 15.501(3) Angstrom, alpha = 79.85(2)degrees, beta = 85.11(2)degrees, gamma = 74.18(3)degrees, Z = 1. The crystalline lattice consists of one-dimensio nal TCNQ units, stacked along the a direction, and it is stabilized by inte ractions with the Fe(III) hexacoordinated complex cations. All of the TCNQ' s are crystallographically equivalent, with bond parameters typical of part ially reduced accepters with a formal charge of 0.5 electron. Two different distances between adjacent TCNQ units are observed, i.e., 3.29 and 3.42 An gstrom, indicating the presence of dimeric (TCNQ)(2)(-) in the chains. The temperature dependence of the magnetic susceptibility was described as due to two contributions: the first one comes from the Curie contribution of th e Fe(III) complex while the second arises from the magnetic exchange intera ctions between the nearest neighbor TCNQ anions. The latter is typical of o ne-dimensional antiferromagnetic chains of S = 1/2 spins, localized on (TCN Q)(2)(-) units, and it could be fitted according to a one-dimensional Heise nberg antiferromagnet model.