The goal of this work was to explore the chemistry and the physics of a family of molecule-based magnets containing three spin carriers, with a fully interlocked structure. The main emphasis was on the coercivity of these magnets, which confers a memory effect on the materials. stands for the radical cation 2-(1-ethylpyridinium-4-yl)-4,4,5,5-tetramethylimidazolin-1-oxyl-3-oxide, and opba stands for ortho-phenylenebis-(oxamato). The crystal structures of the three compounds have been determined. The structure of 1 consists of planar Cu(opba) units with one of the radical cations weakly bound to the Cu 2 ion, the other radical cation being rather isolated. Compounds 2 and 3 are isomorphous. Their structure consists of two interpenetrating graphitelike networks with edge-sharing hexagons. The magnetic properties of the three compounds have been investigated in detail. For compounds 2 and 3 the temperature dependences of the direct current (dc) and alternating current (ac) magnetic responses have been measured along with the field dependence of the magnetization. Both compounds exhibit a long-range magnetic ordering with a spontaneous magnetization. The critical temperatures are 22.8 K and 37 K for 2 and 3, respectively. While 2 is a soft magnet, 3 has been found to be a very hard magnet, with a coercive field depending on the particle size. This coercive field may reach 24 kOe at 6 K for a sample consisting of very small crystals. Mixed materials with the abbreviated formula [Etrad 2 Mn 2À2x Co 2x Cu 3 ] (4Àx) have also been synthesized. Their critical temperatures have been found to vary almost linearly with x. The x dependence of the coercive field has also been investigated and analyzed.

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