1H NMR investigation of the magnetic spin configuration in the molecule-based ferrimagnet [MnTFPP][TCNE]

1H NMR line-shape measurements have been performed in the linear chain molecule-based ferrimagnet [MnTFPP][TCNE].xPhMe (TFPP=tetrakis(4-fluorophenyl)porphinato; TCNE=tetracyanoethylene) as a function of temperature. Hyperfine shifts of opposite sign were observed indicating the presence of two oppositely hyperfine couplings, predominantly between the Mn ions and the 1H nuclei of the planar ring of the [MnTFPP]+ unit. The observation of the hyperfine shifts strongly suggests the existence of two oppositely directed [MnTFPP]+ sites. Since there is no direct exchange coupling between adjacent [MnTFPP] spins, then it can be argued that an ordered spin configuration with antiparallel components may arise from antisymmetric spin-spin exchange interactions. The field independence of the hyperfine shifts at low temperatures and for applied magnetic fields in the range 2-5 T, indicates the presence of ferromagnetic interactions in the ground state of the ferrimagnetic chain.