Magnetic properties of charge transfer complexes of manganese porphyrin derivatives and tetracyanoethylene

A series of charge transfer complexes between tetracyanoethylene and manganese(II) tetraphenylporphyrin derivatives with redox potentials (E ° (Mn3+/2+)) ranging from −0.23 through −0.08 V vs. SCE, were prepared. The magnitude of the charge transfer decreased with the more anodically shifted redox potentials of the porphyrins which have stronger electron withdrawing groups, in the order of phenyl, 4-methoxyphenyl, 2-thienyl, and 4-cyanophenyl substituents at meso positions. The magnitude of the charge transfer reflected in frequency shift of CN vibration of the TCNE. The magnetization curves at very low temperature showed hysteresis. The salt with cathodically-shifted E ° (Mn3+/2+) has a lower Curie temperature (Tc). In other words, the degree of the charge transfer between TCNE and Mn porphyrin responsible for the high TC value.