Thin magnetic films are essential for many applications and this diverse new class of organic magnets [1] is ideally suited for their development due to magnetic ordering temperatures, T c , well above room temperature, [2] modulation/ tuning of properties via organic chemistry methodologies, compatibility with polymers for composites, mechanical flexibility, transparency, low temperature processability, insulating to semiconducting behavior, solubility, etc.[3]Room temperature V[TCNE] x ×yS magnets (T c~4 00 K; x2 ; y~0.5; TCNE = tetracyanoethylene; S = solvent) can be prepared under a variety of conditions via the reaction of TCNE and V(C 6 H 6 ) 2 ×[4a] or V(CO) 6 [4b] in solution (S = CH 2 Cl 2 , acetonitrile, tetrahydrofuran). These magnets, while extremely air sensitive, have numerous potential applications [3] including magnetic shielding.[5] The solvent modulates the magnetic properties by coordination to the metal ion, which blocks spin-coupling pathways and creates structural disorder, [6] suppressing T c . Herein we report the preparation and characterization of thin films of the V[TCNE] x magnet using chemical vapor deposition (CVD) [7] at low temperature.In addition to these CVD-prepared films, Langmuir±Blodgett (LB) techniques have been utilized to make magnets.[8]To form thin films, as well as eliminate the deleterious effect of the solvent, V[TCNE] x films were grown from the gas phase reaction of TCNE and V(CO) 6 (Fig. 1).[9] Film could be easily deposited on glass, quartz, mica, Teflon, NaCl, CsI, gold, silver, aluminum, Si wafer, and amorphous carbon. Typical thicknesses, as measured by optical microscopy, of films on glass substrates after deposition for 12 h were 1±5 mm depending upon the distance from the reaction zone. These substrate-containing films are sufficiently magnetic at room temperature that they are attracted to a magnet (Fig. 2). Unlike solvent-prepared V[TCNE] x ×yS, which decomposed at the diffusion rate of oxygen (sometimes in a pyrophoric manner), [4] these V[TCNE] x films were relatively air stable and could be handled in the air (Fig. 2). The V 2p spectra show that the V 2p 3/2 and V 2p 1/2 lines are split into two components at 514.0, 516.8, 521.5, and 524.3 eV representing both low and high oxidation states of V ion (Fig. 3a).[10b] The 514.0 and 521.5 eV peaks are characteristic of V II , while the 516.8 and 524.3 eV peaks correspond to V V 2 O 5 , whose presence is attributed to surface oxidation. The corresponding O 1s peak is at 532.1 eV (Fig. 3a). The best fit to experimental data was obtained for purely Gaussian peaks, implying a distribution of binding energies arising from a distribution of V±N distances. This is consistent with preliminary powder X-ray diffraction data and transmission electron micrographs, which reveal that V[TCNE] x films are amorphous. The 399.0 eV N 1s peak is asymmetric and has a weak, high-energy satellite, assigned to a shake-up process (Fig. 3b).[10c] A Gaussian deconvolution of the main peak reveals two components (~2:1) at 398.9 a...

No abstract

No abstract

[Fe(TCNE)(NCMe)2][FeCl4] is isolated from the reaction of TCNE and FeCl2(NCMe)2 and orders as a ferrimagnet below 90 K and is the initial member of a new class of magnets. It is the first metal-TCNE magnet with direct bonding between metal ion and [TCNE]*- whose structure has been determined, and it possesses a novel planar mu4-[TCNE]*- spin coupling unit bonded to four FeII's, with an axial pair of MeCNs. The [FeIIICl4]- anion occupies sites between the [FeII(TCNE*-)(NCMe)2]+ layers. [Fe(TCNE)(NCMe)2][FeCl4] has a coercive field of 1730 Oe and a remnant magnetization of 7500 emuK/mol at 50 K.