A family of molecule-based magnets of general formula M[TCNQ] y (M ) Mn, Fe, Co, Ni; TCNQ ) 7,7,8,8-tetracyano-p-quinodimethane) has been synthesized and characterized. The materials have been synthesized from both M a (CO) b and [M(NCMe) 6 ][SbF 6 ] 2 starting materials, complementing previous studies utilizing [M(NCMe) 6 ][BF 4 ] 2 . Magnetic ordering was observed for all materials with T c values between 8 K [M ) Ni from Ni(CO) 4 ] and 60 K {M ) Mn from [Mn(NCMe) 6 ][SbF 6 ] 2 }. The materials from [M(NCMe) 6 ][SbF 6 ] 2 displayed the highest critical temperatures, followed by those from M a (CO) b . With the exception of M ) Ni, the lowest T c 's are obtained from the [M(NCMe) 6 ][BF 4 ] 2 route, which was previously reported. The materials from [M(NCMe) 6 ][SbF 6 ] 2 also exhibit the highest coercivity, followed by those from [M(NCMe) 6 ][BF 4 ] 2 . With the exception of M ) Fe, the materials from M a (CO) b exhibit the lowest coercive fields. In general, magnets made from [M(NCMe) 6 ][SbF 6 ] 2 have a reduced ′′(T) frequency dependence with respect to materials from [M(NCMe) 6 ][BF 4 ] 2 ; thus, they exhibit less glassy magnetic behavior. Elemental analysis data indicate that small amounts of counterions and solvent are present in the products of these reactions, but less than better-coordinating [BF 4 ] -. Thus, the synthetic route has a significant effect on the magnetic properties of the materials, and enhanced T c 's are observed when less-coordinating anions are used. Although the structures of the materials are not known, it is proposed that the S ) 1/2 [TCNQ] •-sp-hybridized Ns bond to multiple metal ions, thereby facilitating magnetic coupling and ordering.

A new family of molecule-based magnets of general formula V[TCNQR(2)](2).zCH(2)Cl(2) has been synthesized and characterized (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane; R = H, Br, Me, Et, i-Pr, OMe, OEt, and OPh). In addition, solid solutions of V[TCNQ](x)()[TCNQ(OEt)(2)](2)(-)(x)().zCH(2)Cl(2) composition have been prepared. Except R = Br, magnetic ordering was observed for all materials, with T(c) values between 7.5 K (R = Me) and 106 K (R = OEt), with R = H at 52 K. The substitution of electron-donating OMe and OEt groups for H in TCNQ increased T(c), whereas the substitution of less electron-donating alkyl groups (with respect to alkoxy groups) decreased T(c). The results of MO calculations indicate that neither the spin nor charge densities of the disubstituted TCNQs are sufficiently different to explain the wide range of critical temperatures. Although the structures of the amorphous materials are not known, it is proposed that the oxygen atom of the [TCNQR(2)](*)(-) acceptor (R = OMe and OEt) and the V(II) interact to form a seven-membered ring. This interaction could stabilize the structure and enhance the magnetic coupling, leading to an increased T(c). The magnetic properties of V[TCNQ](x)()[TCNQ(OEt)(2)](2)(-)(x)().zCH(2)Cl(2) deviated from the expected linear relationship with respect to x, exhibiting magnetic behavior more characteristic of a step function in a plot of T(c) versus x.

A new organic-based magnet, V[TCNP]2.yCH2Cl2 (TCNP = tetracyanopyrazine), has been synthesized, and its magnetic properties have been examined. The amorphous nature of V[TCNP]2.yCH2Cl2 makes it difficult to determine the structure of the material; however, ac and dc magnetic measurements indicate that it is a ferrimagnet below 200 K with a small coercive field of 8 Oe at 5 K.

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A family of amorphous, solid-solution magnets of V x Fe 1-x [TCNE] 2 ‚zCH 2 Cl 2 (TCNE ) tetracyanoethylene; 0 e x e 1) composition has been characterized by IR spectrometry, elemental analysis, and magnetic measurements (ac and dc susceptibility). Substitution of Fe II for V II in V[TCNE] 2 ‚zCH 2 Cl 2 does not significantly alter the T c for x g 0.3, which exceeds room temperature; however, H cr is enhanced by over 2 orders of magnitude, indicating a large increase of random anisotropy. Hence, the magnetic properties of the room-temperature V[TCNE] 2 ‚zCH 2 Cl 2 magnet can be finely tuned via a synthetic chemistry methodology, making this material more amenable to future technologies.