Influence of Water Ligands on Structural Diversity: From a One-Dimensional Linear Coordination Polymer to Three-Dimensional Ferrimagnetic Diamondoid Metal−Organic Frameworks

Four three-dimensional (3D) metal−organic frameworks [Mn3(3-Me-sal)4(py)4]n (1), [Mn3(4-Me-sal)4(py)4(MeOH)]n·n(H2O) (2), [Mn3(5-Me-sal)4(py)4(H2O)2]n·n(MeOH) (3), and [Mn3(3-Me-sal)4(4-Me-py)4]n (4) and the one-dimensional (1D) coordination polymer {[Mn2(4-Me-sal)2(4-Me-py)2(H2O)2(MeOH)2][Mn(4-Me-sal)2(4-Me-py)2]}n (5) have been synthesized, where x-Me-salH2 = x-methyl salicylic acid (x = 3, 4, 5), py = pyridine, and 4-Me-py = 4-methyl-pyridine. The 3D frameworks of compounds 14 can be described as diamondoid networks. Magnetic studies show that weak MnII−MnIII antiferromagnetic interactions (in the range of −0.55 to −0.22 K) mediated by syn-anti carboxylate bridges are present in all compounds. While 5 remains paramagnetic down to 1.8 K, the 3D networks exhibit long-range ferrimagnetic ordering below 7.4 K for 1, 4.6 K for 2, 3.0 K for 3, and 7.7 K for 4. The decrease of the critical temperature reflects the increase of the coordination number around the Mn(II) site from four in 1, five in 2, and six in 3 that lower the bond strength and the magnetic interactions. This result also reinforces the hypothesis that the structures of 1 and 4 are similar as suggested by the X-ray analysis.