Two-dimensional molecular-based ferrimagnets incorporating decamethylmetallocenium cations

Four new molecular-based magnets have been synthesized, and their magnetic properties have been investigated in detail. Their formulae are [M'(C(5)Me(5))(2)](2)M(2)[Cu(opba)](3) .(DMSO)(x)(H2O)(y) with M' = Fe, M = Mn, x = 5, y = 4 (1), M' = Fe, M = Co, x = 6, y = 4 (2), M' = Co, M = Mn, x = 5.5, y = 4 (3) and M' = Co, M = Co, x = 5.5, y = 4 (4) [opba = ortho-phenylenebis (oxamato)]. The decamethylmetallocenium cations [Fe(C(5)Me(5))(2)](+) and [Co(C(5)Me(5))(2)](+) are most probably located between the anionic honeycomb-like networks Mn-2 [Cu(opba)](3) and Co-2[Cu(opba)](3). Compounds 1-4 are two-dimensional ferrimagnets exhibiting a spontaneous magnetization below a critical temperature, T-c, of 14 K for 1, 27 K for 2, 13 K for 3 and 27.5 K for 4. Compounds 1 and 3, with Mn-II ions in the layered framework structure, do not exhibit magnetic hysteresis, while 2 and 4, with Con in the layered framework structure, exhibit a wide magnetic hysteresis loop. The coercive fields at 2 K are found to be equal to 3.5 x 10(3) Oe for 2 and 5.3 x 103 Oe for 4. The latter is one of the largest values reported so far for a molecular-based magnet. The Mossbauer spectra for 1 and 2 have been recorded at various temperatures. These spectra suggest that the [Fe(C(5)Me(5))(2)](+) units occupy two sites between the layers with a 50/50 distribution, and that they are not directly involved in the long-range magnetic ordering.