Heterometallic Mn4IIILn2 (Ln = Dy, Gd, Tb) Cross-Shaped Clusters and Their Homometallic Mn4IIIMn2II Analogues

The employment of di-2-pyridyl ketone, (py)(2)CO, in heterometallic Mn/4f and homometallic Mn cluster chemistry has yielded six Mn(4)(III)Ln(2) and two Mn-4(III) Mn-2(II) structurally related clusters, namely, [Mn(4)Ln(2)O(2){(py)(2)CO2}(4)(NO3) (2-)(RCO2)(2)(H2O)(6)](NO3)(2) (Ln = Gd, 1, 5; Dy, 2; Tb, 3; R = Et, 1-3; Me, 5), [Mn4Dy2O2{(py)(2)CO2}(4)(NO3)(4)(EtCO2) (2)(H2O)(3)(MeOH)]0.7MeOH0.8H(2)O (40.7MeOH0.8H(2)O), [Mn4Gd2O2{(py)(2)CO2}(4)(NO3)(4)(C6H4ClCO2)(2)(MeOH) (2)(py)(2)]2MeOH (62MeOH), [Mn O-6(2){(py)(2)CO2}(4)py)(4)(H2O)(4)](ClO4)(4)4H(2)O (74H(2)O), and [Mn O-6(2){(py)(2)CO2}(4)(NO3)(4)(py)(4)] (8), where (py)(2)CO22- is the dianion of the gem-diol derivative of (py)(2)CO. The compounds possess a new type of cross-shaped structural core, which in the case of 1-6 is essentially planar, whereas in 7 and 8 it deviates from planarity. Clusters 1-6 are rare examples of Mn/4f species bearing (py)(2)CO or its derivatives, despite the fact that this ligand has been well-studied and proven a rich source of more than 200 metal compounds so far. Variable-temperature, solid-state direct-current and alternating-current magnetization studies were performed on complexes 1-5, 7, and 8 revealing that the dominant exchange interactions between the metal ions are antiferromagnetic and indicating ground-state spin values of S = 5 (for 1), 6 (for 5), and 2 (for 7 and 8).