Solvent dependence of the structure and magnetic ordering of ferrimagnetic manganese(III) meso-tetraphenylporphyrin tetracyanoethenide, [MnTPP]+[TCNE]•-•x(solvent).: Evidence for orientationally disordered [TCNE]•-

Tetraphenylporphinatomanganate(III) tetracyanoethenide, [MnTPP][TCNE]: is the prototype of a growing family of linear chain (1-D) coordination polymers that magnetically order as ferrimagnets. [MnTPP][TCNE]. xS [S = PhMe (x = 2), 1,2-C6H4Me2 (X = 1), 1,2-C6H4Cl2 (X = 3), 1,2,4-C6H3Cl3 (x = 2), and 1,3-C6H4Cl2 (x = 2)] have been prepared and structurally and magnetically characterized. Ail form 1-D chain structures with intrachain Mn Mn separations ranging from 9.202 to 10.218 Angstrom. The 173 K crystal structure of [MnTPP][TCNE]. 2PhMe has been rerefined, revealing that the [TCNE](.-) is 2-fold-disordered and coordinated to Mn-III by a pair of trans cyano nitrogen atoms to form parallel one-dimensional chains. The two orientations of [TCNE](.-) are related by a 180 degrees rotation about the diagonal axis joining the trans nitrogen atoms bound to Mn-III. The major form has an occupancy of 83.3(4)% with a Mn-N-TCNE distance of 2,328(3) Angstrom and a MnNC angle of 146.8(8)degrees. The minor form, with 16,7(4)% occupancy, has a Mn-N-TCNE distance of 2.176(15) Angstrom and a MnNC angle of 152.3(39)degrees Lattice packing and molecular bonding imply static as opposed to dynamic disorder. The magnetic properties depend on the type and quantity of the solvent present in the structure. Desolvation via heating in n-octane (127 degreesC), n-dodecane (216 degreesC), and/or vacuum thermolysis (175 degreesC) leads to numerous different desolvated materials with differing magnetic properties. At higher temperatures the magnetic susceptibility can be fit by the Curie-Weiss expression, chi proportional to (T - theta)(-1), with theta = 44, 52, 72, 55, and 77 K for the toluene, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene solvates, respectively. The T-c's were taken as the maximum in 10 Hz chi'(T) and are 7.8, 9.2, 11.3, 10.8, and 8.2 K for the PhMe, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene solvates, respectively. Upon desolvation the T-c's increase for the PhMe, 1,2-xylene, 1,2,4-trichlorobenzene solvates and decrease for the 1,2- and 1,3-dichlorobenezene solvates. The compounds show one-dimensional ferrimagnetic exchange behavior at high temperatures with intrachain exchange of J/k(o) = -63, -99, -234, -100, and -200 K for toluene, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene solvates, respectively, as determined from fits to the Seiden expression, which models isolated 1-D interactions among alternating S = 2 classical and S = (1)/(2) quantum spins. For variation in the temperature at which the peak occurs per decade of frequency, phi, (DeltaT(f)/T-f)/Delta (log omega) is 0.167, 0.168, 0.066, 0.171, and 0.024 for toluene, 1,2-xylene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, and 1,2,4-trichlorobenzene, respectively, typical of spin glass behavior. Since [TCNE](.-) is only disordered for the PhMe solvate and all five solvates exhibit spin glass behavior, the spin glass behavior cannot be attributed to this disorder.