Molecular Magnetism ofVanadium (II), Nickel (II) and Cobalt (II) Compounds with Tetracyanoethylene and Nickel bis(maleonitriledithiolate) Bridging Groups
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The ferromagnetically ordered magnetic material Ni[TCNEh·zCH2Ch (z ~ 0.5) with transition temperature Tc = 13 K (e = 2.44 K) is reported for the first time from the reaction ofNi(CO)4 and TCNE. A new family of room temperature molecular magnets of composition VxNiI_x[TCNEh·zCH2Ch (0 < x < 1) with transition temperatures up to Tc = 391 K have been characterized by infrared spectroscopy and elemental analysis. Herein we report the alternating and direct current magnetic properties of this material. Substitution of NiII for VII is not shown to significantly change Tc for x ~ 0.05, but is shown to increase random site occupancy resulting in spin glass behavior. Her increases as x ~ 0, 1; Hrem locally increases as x ~ 0.1 and globally increases as x ~ 1, though all solid solutions are shown to be soft magnets. A coupling mechanism is proposed based on direct exchange. Thus the magnetic properties of V[TCNEh·zCH2Ch may be tuned via synthetic chemistry methodology making this material more amenable to future technology. The reaction ofx TBA[Ni(mnt)2] and M(NCMe)6(SbF6)2 (M = Co, Ni; x = 2, 3) has been observed. For M = Co, the product Co(NCMe)2[Ni(mnt)2h is presumed, though for M = Ni, infrared spectroscopy indicates co-crystalization of the product with (TBAt and (SbF6f or a more complex product incorporating both counter ions to maintain charge neutrality. Temperature dependent magnetization indicates neither product magnetically orders. Finally, single crystals of TBA[Ni(mnt)2] suitable for polarized neutron diffraction (~50 mg) were grown by slow ether diffusion to determine the spin density ofthe ligand.
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