1H NMR investigation of the magnetic spin configuration in the molecule-based ferrimagnet [MnTFPP][TCNE] -: art. no. 064422

H-1 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 H-1 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.