Ferromagnetism in CuII4 and CoII4 Complexes Derived from Metal‐Assisted Solvolysis of Di‐2,6‐(2‐pyridylcarbonyl)pyridine: Syntheses, Structures, and Magnetic Properties

Abstract

AbstractMetal‐assisted solvolysis of di‐2,6‐(2‐pyridylcarbonyl)pyridine (pyCOpyCOpy, dpcp) by M(O2CMe)2·xH2O (MII = CuII, CoII) led to complex [Cu4{pyC(O)2pyC(O)(OEt)py}(O2CMe)5(EtOH)2] (1), when the reaction was carried out in EtOH, and to complex [Co4{pyC(O)(OMe)pyC(O)(OMe)py}2(O2CMe)2(N3)2] (2), when the reaction was carried out in MeOH in the presence of azide anions. Complex 1 consists of four CuII ions bridged by the hemiacetal‐gem‐diol form of the ligand, which is found in a μ4‐η2:η2:η2:η1:η1:η1 coordination mode. It exhibits ferromagnetic couplings among all nearest neighbors and antiferromagnetic next‐nearest‐neighbor interactions (J12 = J1 = 48.0 cm–1, J23 = J2 = 20.4 cm–1, J34 = J3 = 16.9 cm–1, J24 = J4 = –10.0 cm–1, H = –2ΣJiJj spin Hamiltonian formalism), which stabilize an S = 1 ground state and an S = 2 state lying closely above it. Complex 2 consists of four CoII ions bridged by the bis(hemiacetal) form of the ligand, which is found in a μ3‐η2:η2:η1:η1:η1 coordination mode, and by μ3‐azido ligands. It also exhibits ferromagnetic interactions due to the μ3–1,1,1 bridging mode of the azido ligands, which is known to promote ferromagnetic interactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)