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- A molecular 'LEGO®' approach to high-spin triangular {MnIIILn2} clusters from {MnIII} and {Ln2} metalloligandsPublication . Pantelis, Konstantinos N.; Cunha-Silva, Luís; Saber, Mohamed R.; Dunbar, Kim R.; Alexandropoulos, Dimitris I.; Stamatatos, TheocharisABSTRACT: A stepwise "LEGO (R)-brick" strategy has been employed for the targeted assembly of rare low-nuclearity MnIII/LnIII clusters from preformed molecular building units. The mononuclear MnIII metalloligand (Pr2NH2)[MnIII(sacb)2] (1; sacbH2 = N-salicylidene-2-amino-5-chlorobenzoic acid) was combined with newly isolated dinuclear lanthanide complexes [Ln2(sacb)(sacbH)3L(MeOH)] [LnIII = Dy (2), Gd (3); L- = 2-amino-5-chlorobenzoate], affording the trinuclear heterometallic compounds [MnIIILn2(sacb)3(sacbH)2L] [LnIII = Dy (4), Gd (5)]. Single-crystal X-ray diffraction studies revealed that 4 and 5 possess triangular {MnIIILn2(mu-O2CR)3}6+ cores, representing the first structurally characterized triangular {MnIIILn2} complexes and rare examples of triangular {MLn2} (M = any 3d-metal ion) clusters. Magnetic studies have demonstrated that the MnIII-free {Dy2} precursor 2 displays weak field-induced slow relaxation of magnetization, whereas incorporation of the Jahn-Teller active MnIII ion leads to ferromagnetically coupled {MnIIILn2} species. In particular, the {MnIIIGd2} analogue 5 exhibits a high-spin ground state of S = 9, with weak ferromagnetic MnIII & ctdot;GdIII and GdIII & ctdot;GdIII exchange interactions. Although no slow magnetic relaxation was observed for the trinuclear complexes, the results demonstrate that controlled integration of a MnIII metalloligand can promote ferromagnetic exchange in preassembled {Ln2} units and provide a direct route to structurally defined high-spin 3d/4f triangles.