| Abstract
| - Mononuclear complexes of formula M(L)m(X)2 (M = Zn, Cd; L = PNN, PN; X- = N3-, NCS-; m = 2, 4) were synthesized and structurally and magnetically characterized. As suggested by the magnetic behavior of the compounds, the low-temperature X-ray structures show a clear structural change with respect to the room-temperature structures explaining the sudden breaks observed in the χMT versus T curves. The experimental magnetic behaviors were perfectly reproduced by a dimer model and an alternating chain model. For all these complexes the crystal structures favor significant overlap between molecular magnetic orbitals leading to rather strong intermolecular antiferromagnetic interactions.
- Four new mononuclear complexes of formula Cd(PN)4(NCS)2 (A), Cd(PNN)4(N3)2(B), Zn(PNN)4(N3)2(C), andZn(PNN)2(NCS)2(D), where PNN stands for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and PN for2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl, were synthesized and structurally and magnetically characterized.The X-ray structures of compounds B and C were also determined at 90 K. Compounds A−C crystallize in thetriclinic space group P1̄ (No. 2), and D crystallizes in the monoclinic space group P21/m (No. 11). A−C adopt acentrosymmetric distorted octahedral geometry in which the metal ions are bonded to four radical ligands throughthe nitrogen atom of the pyridyl rings and the azido or thiocyanato ligands occupy the apical positions. CompoundD adopts a distorted tetrahedral geometry in which the zinc ion is bonded to two radicals and two thiocyanatoligands. As suggested by their magnetic behavior, the low-temperature X-ray structures of B and C show thatthese compounds undergo a clear structural change with respect to the room-temperature structures. The experimentalmagnetic behaviors were perfectly reproduced by a dimer model for A−C and an alternating chain model for Dwhile the sudden breaks observed in the χMT versus T curves for B and C were well accounted for by the high-and low-temperature X-ray structures. For all these complexes the crystal structures favor significant overlap betweenmolecular magnetic orbitals leading to rather strong intermolecular antiferromagnetic interactions.
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