Linear Chain Ferromagnetic Charge Transfer Compounds

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(C 5 Me 5 ) 2 ] + ·[TCNQ] − · exhibits metamagnetic behavior. The similarly structured [TCNE] − · and [C 4 (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] − ·, [C 4 (CN) 6 ] − ·, and [TCNQ] − · salts, respectively. The ferromagnetic [TCNE] − · salt exhibits zero field Zeeman split 57 Fe 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.