Novel Topologies in Vanadium-bis-ß-Diketone Chemistry: A [V4] and a [V6] Metallacyclophane

Exploring the chemistry of vanadyl ions (VO2+) with bis-β-diketone ligands, in pyridine reactions of vanadyl sulfate with 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-benzene (H4L1) and 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-pyridine (H4L2), two novel clusters, [(VIVO)4(H2L1)4(py)4] (1) and [(VVO)4(VIVO)2 (O)4(L2)2(py)6] (2) were prepared and characterized. Due to the conformational flexibility of the ligands, both entities exhibit very peculiar metal topologies and composition, differing significantly from structural patterns established in the related chemistry of divalent 3d metals. Structural analysis also unveils the existence of the most complex metallamacrocycles from this family to date. Studies of the magnetic properties via bulk magnetization measurements and EPR spectroscopy confirmed the existence of uncoupled long-distant S = 1/2 metal centers and the spin ground states S = 2 and S = 1 of the clusters.