339151-44-9Relevant academic research and scientific papers
Solvent dependence of the structure and magnetic ordering of ferrimagnetic manganese(III) meso-tetraphenylporphyrin tetracyanoethenide, [MNTPP]+[TCNE]?-·x(solvent). Evidence for orientationally disordered [TCNE]?-
Hibbs,Rittenberg,Sugiura,Burkhart,Morin,Arif,Liable-Sands,Rheingold,Sundaralingam,Epstein,Miller
, p. 1915 - 1925 (2001)
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. All form 1-D chain structures with intrachain Mn···Mn separations ranging from 9.202 to 10.218 A. The 173 K crystal structure of [MnTPP][TCNE]·2PhMe has been rerefined, revealing that the [TCNE]?- is 2-fold-disordered and coordinated to MnIII by a pair of trans cyano nitrogen atoms to form parallel one-dimensional chains. The two orientations of [TCNE]?- are related by a 180° rotation about the diagonal axis joining the trans nitrogen atoms bound to MnIII. The major form has an occupancy of 83.3(4)% with a Mn-NTCNE distance of 2.328(3) A and a MnNC angle of 146.8(8)°. The minor form, with 16.7(4)% occupancy, has a Mn-NTCNE distance of 2.176(15) A and a MnNC angle of 152.3(39)°. 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 °C), n-dodecane (216 °C), and/or vacuum thermolysis (175 °C) leads to numerous different desolvated materials with differing magnetic properties. At higher temperatures the magnetic susceptibility can be fit by the Curie-Weiss expression, X ∝ (T - θ)-1, with θ = 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 Tc's were taken as the maximum in 10 Hz X′(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 Tc'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/kb = -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, φ, (ΔTf/Tf)/Δ(log ω) 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.
