2024-03-28T13:17:53Zhttp://digital.csic.es/dspace-oai/requestoai:digital.csic.es:10261/191272021-10-27T07:42:30Zcom_10261_31com_10261_3com_10261_46com_10261_10252col_10261_284col_10261_299col_10261_10253
Roques, Nans
Maspoch, Daniel
Luis, Fernando
Camón, Agustín
Wurst, Klaus
Datcu, Angela
Rovira, Concepció
Ruiz Molina, Daniel
Veciana, Jaume
2009-11-30T08:59:07Z
2009-11-30T08:59:07Z
2008
Journal of Material Chemistry 18(1): 98-108 (2008)
0959-9428
http://hdl.handle.net/10261/19127
10.1039/b713705b
1364-5501
http://dx.doi.org/10.13039/501100000780
http://dx.doi.org/10.13039/501100006280
An octahedral hexacarboxylic polychlorotriphenylmethyl radical (PTMHC) and its hydrogenated precursor (aH-PTMHC) have been reacted with Cu(II) and 4,4'-bipyridine to prepare two isomorphic three-dimensional (3-D) coordination polymers of formula [Cu6(PTMHC)2(4,4'-bipy)3(H20)12]n(1) and [Cu6(aH-PTMHC)2(4,4'-bipy)3(EtOH)6(H20)6]n (2). Both 3-D structures can be described as two interpenetrating primitive cubic nets connected through bipyridine linkers, which defines an unusual topology with Schläfi symbol of (62·81)·(66·89). Magnetic properties of both metal-organic frameworks have been studied in detail. 2 shows weak antiferromagnetic interactions between Cu(II) ions at low temperature. In contrast, 1 reveals unexpected metal-radical ferromagnetic interactions (θ=2.1 (2) K). Information on the existence of magnetic ordering and the nature of the ordered phase for 1 has been investigated via very low temperature magnetic susceptibility measurements. Surprisingly, the experimental data indicate the occurrence of 3-D antiferromagnetic ordering below 0.5 K. This latter phenomenon has been explained with specific heat measurements. Experimental results reveal the coexistence of relatively strong ferromagnetic interactions with weaker antiferromagnetic ones, mediated through the bipyridine linkers, which finally determine the low temperature magnetic structure. A deeper study of the data allows the analysis of the magnetic behavior of 1 as a 3-D antiferromagnet, with Tc = 0.39 K, with ferromagnetic exchange interactions that do not propagate with equal strength along the three crystallographic directions above this temperature.
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A hexacarboxylic open-shell building block: synthesis, structure and magnetism of a three-dimensional metal-radical framework
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