Observation of Magnetic Ordering as high as 28 K for meso-tetrakis(4-halophenyl)porphyrinatomanganese(III) Tetracyanoethenide, [MnTXPP][TCNE] (X = F, Br, I), D. K. Rittenberg, J. S. Miller, Inorg. Chem. 38, 4838-4848 (1999).

The toluene solvates of meso-tetrakis(4-halophenyl)manganese(III) tetracyanoethenide, [MnTFPP][TCNE] (1F), [MnTBrPP][TCNE] (1Br), and [MnTIPP][TCNE] (1I) have been prepared and the magnetic and thermal properties have been determined and compared to [MnTClPP][TCNE] (1Cl). 1Br and 1I form uniform 1-D chains with each [TCNE]^.- being trans-µ-N-s-bound to Mn^III with Mn-N distances of 2.293 (1Br), 2.276 (1I) , which are a bit longer than 2.267 Å observed for 1Cl. The Mn-N-C angles are 167.2, 168.1 and 158.7, while intrachain Mn^...Mn separations are 10.189, 10.277 and 10.101 Å. The magnetic susceptibilities for 1Br and 1I can be fit by the Curie-Weiss expression with high temperature (T > 200 K) q and low temperature (T < 110 K) effective q' values of —53 and 13 K and —79 and 30 K, respectively, compared to —60 and 13 K in 1Cl. q is not observed for 1F; however, q' is 70 K. The magnetic data are consistent with linear chain ferrimagnets comprised of antiferromagnetically coupled S = 2 Mn^III sites and S = 1/2 [TCNE]^.- sites with the antiferromagnetic intrachain coupling, Jintra/kB (kB = Boltzmann's constant) determined from fits to the Seiden expression, of -225, -33, -30, and -53 K for the 1F, 1Cl, 1Br, and 1I, respectively. Hysteresis with coercive fields at 2 K of 20.0, 6.7, 4.0, and 15.9 kOe was observed for the 1F, 1Cl, 1Br, and 1I, respectively. Metamagnetic behavior is observed below 10 K for 1F, and below 5 K for both 1Br and 1I. The observed critical fields of 21.8, 6.8, 4.1, and 15.8 kOe, were observed for 1F, 1Cl, 1Br, and 1I at 2 K, respectively. The ordering temperatures, T_c, determined from the maxima in the c'(T) data taken at 10 Hz, are 28.0, 8.8, 8.0, and 6.5 K for 1F, 1Cl, 1Br, and 1I, respectively. The 28 K T_c for 1F is the highest reported for this family of magnets.