Linear Chain Ferromagnetic Charge Transfer Compounds

Abstract
Charge transfer complexes possessing a … DADA … structure with both the donor, D, and acceptor, A, being S = 1/2 radicals may exhibit cooperative magnetic phenomena. The complex [Fe(C5Me5)2]+·[TCNQ]· exhibits metamagnetic behavior. The similarly structured [TCNE]· and [C4(CN)6]· complexes are ferromagnets, whereas the [DDQ]· salt is a paramagnet. The high temperature magnetic susceptibility obeys the Curie‐Weiss expression with θ = + 30, + 30, and + 3 for the [TCNE]·, [C4(CN)6]·, and [TCNQ]· salts, respectively. The ferromagnetic [TCNE]· salt exhibits zero field Zeeman split 57Fe Mossbauer spectra with an internal field of 425.6 kOe at 4.23 K. After reviewing the current papers discussing ferromagnetism in molecular (organic) compounds, a qualitative model consistent with the necessary bulk spin alignment required for a ferromagnet is presented.