PUB - Publikationen an der Universität Bielefeld

In order to further optimize our triplesalen-based single-molecule magnets, we have synthesized the triplesalophen ligand H(6)baron(Me), where the completely sp(2)-hybridized ligand backbone should enable almost planar complexes. Here, we report the new complexes [(baron(Me)){(FeCl)-Cl-III}(3)], [(baron(Me)){Fe-III(CN)(2)}(3)](3-), and [(baron(Me)){Cr-III(CN)(2)}(3)](3-). As intended the local anisotropy axes, defined by the cyanide ligands, deviate only by ten degrees from the molecular C-3-axis. The exchange coupling in [(baron(Me)){Fe-III(CN)(2)}(3)](3-) is ferromagnetic with J = 2.2 cm(-1) but antiferromagnetic in [(baron(Me)){Cr-III(CN)(2)}(3)](3-) with J = -1.76 cm(-1). The ferromagnetic coupling in the Fe-III low-spin complex is rationalized by a good pi overlap of the d(yz) magnetic orbital with the O(p(z)) orbitals of the central phloroglucinol unit. The three unpaired electrons of the Cr-III ions in [(baron(Me)){Cr-III(CN)(2)}(3)](3-) provide competing spin-delocalization and spin-polarization pathways, which explains the overall antiferromagnetic coupling. These two complexes are the first l.s. Fe-III and Cr-III complexes of triplesalen-like ligands and emphasize the strong impact of the specific electronic configuration on the spin-polarization mechanism via the central phloroglucinol. The potential of [(baron(Me)){Fe-III(CN)(2)}(3)](3-) and [(baron(Me)){Cr-III(CN)(2)}(3)](3-) as molecular building blocks for nonanuclear complexes by coordination to the six cyanides is discussed.