Structure and magnetic properties of (meso-tetraphenylporphinato)manganese(III) bis(dithiolato)nickelates

The crystal structures of MnTPP]{NiS2C2H(CN)]2} MnTPP = (meso-tetraphenylporphinato)manganese(III)] and MnTPP]{NiS2C2(CN)2]2} have been determined. These salts possess trans-mu-coordination of S = 1/2 {NiS2C2H(CN)]2}*- and {NiS(2)C(2)(CN)(2)](2)}*- to Mn(III) and form parallel 1-D coordination polymer chains exhibiting nu(CN) at 2210 and 2200 and 2220 and 2212 cm(-1), respectively. The bis(dithiolato) monoanions are planar and bridge two cations with MnN distances of 2.339(16), and 2.394(3) A, respectively, which are comparable to related MnN distances observed for MnTPP]TCNE].x(solvates). In addition, MnTP'P]{NiS2C2(CN)2]2} {H2TP'P = meso-tetrakis3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin] and MnTP'P(OH2)]{NiS2C2(CN)2]2} were prepared. The latter forms isolated paramagnetic ions. The room-temperature values of chiT for 1-D MnTPP]{NiS2C2H(CN)]2}, MnTPP]{NiS2C2(CN)2]2}, and MnTP'P]{NiS2C2(CN)2]2} are 2.55, 3.28, and 2.86 emu K/mol, respectively. Susceptibility (chi) measurements between 2 and 300 K reveal weak antiferromagnetic interactions with theta= -5.9 and -0.2 K for MnTPP]{NiS(2)C(2)H(CN)](2)} and MnTPP]{NiS2C2(CN)2]2}, respectively, and stronger antiferromagnetic coupling of -50 K for MnTP'P]{NiS2C2(CN)2]2} from fits of chi(T) to the Curie-Weiss law. The 1-D intrachain coupling, J(intra), of MnTPP]{NiS2C2H(CN)]2} and MnTPP]{NiS2C2(CN)2]2} was determined from modeling chiT(T) by the Seiden expression (H = -2JSi.Sj) with J/kB = -8.00 K (-5.55 cm(-1); -0.65 meV) for MnTPP]{NiS2C2H(CN)]2}, J/kB = -3.00 K (-2.08 cm(-1); -0.25 meV) for MnTP'P]{NiS2C2(CN)2]2}, and J/kB = -122 K (-85 cm(-1)) for MnTP'P]{NiS2C2(CN)2]2}. These observed negative J(intra)/kB values are indicative of antiferromagnetic coupling. These materials order as ferrimagnets at 5.5, 2.3, and 8.0 K, for MnTPP]{NiS2C2H(CN)]2}, MnTPP]{NiS2C2(CN)2]2}, and MnTP'P]{NiS2C2(CN)2]2}, respectively, based upon the temperature at which maximum in the 10 Hz chi'(T) data occurs. MnTP'P]{NiS2C2(CN)2]2} has a coercivity of 17,700 Oe and remanent magnetizations of 7250 emu Oe/mol at 2 K and 17 Oe and 850 emu Oe/mol at 5 K; hence, upon cooling it goes from being a soft magnet to being a very hard magnet.