Three-Dimensional Supramolecular Architectures with Mn-II Ions Assembled from Hydrogen Bonding Interactions: Crystal Structures and Antiferromagnetic Properties

Two novel cocrystal Mn-II compounds were successfully synthesized. The composition of two kinds crystals correspond to [Mn(hfac)(2)L-2(a)center dot Mn(hfac)(2)L-a(H2O)center dot Mn(hfac)(2)(H2O)(2)] (1) and [Mn(hfac)(2)L-2(b)center dot Mn(hfac)(2)(H2O)(2)center dot 0.5(C6H14)] (2) [L-a = 1,3-bis(1'-oxyl-3'-oxido-4',4',5',5'-tetramethyl-4,5-dihydro-1H-imidazol-2-y1) benzene; L-b = 1-(1'-oxyl-4',4',5',5'-tetramethylimidazolin-2-yl)-3-(1'-oxyl-3'-oxo-4',4',5',5'- tetramethylimidazolin-2-yl)benzene; hfac = hexafluoroacetylacetonato). Surprisingly, the compounds were not polymeric or clusters but, more interestingly, different ratio biradical-metal coordination compound cocrystals. The extensive intramolecular H-bonds are the cause of formation of the cocrystal structures by assembly in the two manganese(II) derivatives; and another factor is the halogen bonds between CF3 of hfac groups. Furthermore, three-dimensional supramolecular architectures were formed. The magnetic susceptibility of both compounds showed strong antiferromagnetic interactions involving the coordinated radical unit and the metal and lesser contribution from ferromagnetic interactions between the radical units. For compound 1, a good fit was obtained for g(Mn) = 2.08, g(rad) = 2.00 (fixed), J(1) = -294.3 cm(-1), J(2) = 6.2 cm(-1) and J(3) = 10.8 cm(-1). A reasonable fit for compound 2 was obtained for g(Mn) = 2.04, g(rad) = 2.00 (fixed), J(1)' = -273.4 cm(-1) and J(2)' = 8.6 cm(-1).