Molecular/Organic Ferromagnets

摘要: Quantitative bulk ferromagnetic behavior has been established for the molecular/organic solid [Fe(III)(C(5)Me(5))(2)].(+)[TCNE].(-). Above 16 K dominant magnetic interactions are along a 1-D chain and, near T(c), 3-D effects as evidenced by value of critical exponents dominate susceptibility. The extended McConnell model was developed and provides synthetic chemist with guidance making new molecular materials to study cooperative coupling in systems. Assuming electron-transfer excitation arises from POMO, mechanism requires stable radicals (neutral, cations/anions, or ions small diamagnetic counterions) non-half-filled POMO. lowest excited state formed via virtual charge transfer (retro forward) must also have same spin multiplicity mix ground state. These requirements limit structure radical D(2d) C>/=(3) symmetry where breaking distortions do not occur. Intrinsic doubly triply degenerate orbitals necessary accidental degeneracies suffice. To achieve ferromagnetism, be throughout microscopic discussed. met Additionally this suggests that Ni(III) Cr(III) analogs should antiferromagnetic ferrimagnetic, respectively, preliminary data suggest. Additional studies test further develop consequences these concepts. Some solids comprised linear chains alternating metallocenium donors (D) cyanocarbon acceptors (A) S = 1/2 (...D.(+)A.(-)D.(+)A.(-)...) exhibit phenomena, is, ferro-, antiferro-, ferri-, metamagnetism. For [Fe(III)(C(5)Me(5))(2)].(+)[TCNE](-). (Me methyl; TCNE tetracyanoethylene), is observed below Curie temperature 4.8 K. A configuration mixing charge-transfer understand function electron direction transfer. This predicts valence orbital mixes Ferromagnetic all directions ferromagnet. Thus, primary, secondary, tertiary structures crucial considerations design ferromagnets.