Transition Metal Ion Directed Self‐Assembly of Polynuclear Coordination Complexes: Structural Characterization and Magnetic Properties

The reactions of different transition metals with the multidentate ligand N , N ′‐bis(1,3,4‐thiadiazol‐2‐yl)‐2,6‐pyridinedicarboxamide (btapca) afford six new polynuclear complexes: the hexanuclear complexes [{Zn 6 (O) 2 (btapca) 4 }·3DMF·2H 2 O] ( 1 ) and [{Zn 6 (O) 2 (btapca) 4 }·DMF·MeOH·H 2 O] ( 2 ); the pentanuclear complexes [{Zn 5 (OH) 2 (btapca) 4 }·4DMF·H 2 O] ( 3 ), [{Co 5 (OH) 2 (btapca) 4 }·4DMF·MeOH·H 2 O] ( 4 ) and [{Ni 5 (OH) 2 (btapca) 4 }·4DMF·MeOH] ( 5 ); and the trinuclear complex [{Fe 3 (OH)(btapca) 3 }·2DMF·2MeOH] ( 6 ). The dominant characteristic of these polynuclear complexes is that there are μ 3 ‐ or μ 4 ‐oxygen atoms in the metal polyhedrons. The hexanuclear complexes 1 and 2 show similar octahedral features based on zinc centers. The five metal centers in complexes 3 , 4 and 5 arrange into two triangles with one common vertex. As for complex 6 , three iron( II )/iron( III ) atoms form a plane with a μ 3 ‐OH − in the center. We also report the magnetic properties of complexes 4 , 5 and 6 . Complex 4 exhibits intramolecular antiferromagnetic exchange, while the analogous complex 5 is dominated by very strong intramolecular ferromagnetic coupling. The trinuclear complex [{Fe 3 (OH)(btapca) 3 }·2DMF·2MeOH] ( 6 ) shows comparable weak antiferromagnetic coupling. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)