Theoretical study of effective exchange integrals for ferromagnetic phenylenevinylene polymers with nitroxides. Possibilities of organic ferro- or ferri-magnetic solids

Molecular orbital calculations were carried out for pendant-type ferromagnetic phenylenevinylene oligomers with nitroxide groups in order to elucidate variations of the effective exchange integrals with oligomer size, conformational change and spin defects generated in the dehydrogenation process of NOH groups in the precursor oligomers. It was shown that the ferromagnetic effective exchange interactions between the nearest neighbor nitroxides are about 50-80 cm^-1, but they decrease with the internal rotation and spin defect. The interchain interactions between the oligomers are antiferrornagnetic, and therefore they should be controlled by introduction of spacer group, showing a possibility to obtain the high T_C organic ferrimagnet induced by one-electron transfer between the oligomer and spacer.