Rational Self-Assembly of Tricobalt Extended Metal Atom Chains and [MF6]2– Building Blocks into One-Dimensional Coordination Polymers

Abstract

Following our recent work on the first crystallographically characterized coordination polymers based on tricobalt extended metal atom chains (EMACs), namely, [Co3(dpa)4MF6]·2DMF [M = ZrIV (1), SnIV (2), and ReIV (3); Hdpa = 2,2′-dipyridylamine; DMF = N,N′-dimethylformamide], we have generalized our synthetic approach based on robust fluoride complexes to prepare new self-assembled one-dimensional (1D) polymers formed by [Co3(dpa)4]2+ and 5d [MF6]2– [M = IrIV (4) and OsIV (5)] building blocks. These 1D complexes are isostructural and crystallize in the P4/ncc space group such that the fourfold axis is coincident with the metal axes of the rigorously linear chains. Magnetic studies reveal ferromagnetic coupling between the S = 1/2 {Co3} and [MF6]2– units in 3 and 4, whereas the nonmagnetic [MF6]2– linkers of 1 and 5 mediate antiferromagnetic coupling between the {Co3} spins. For 2, no significant exchange coupling was observed. Spin-crossover behavior, which was observed for the parent [Co3(dpa)4Cl2] complex, was not detected for 1–5 up to 300 K. This work demonstrates that EMACs and [MF6]2– complexes can be considered as appealing building blocks for the design of new functional coordination networks.