Synthesis, crystal structure and magnetic properties of [Mn((1R, 2R)-Salcy)N3/NCS] complexes: Solvent dependent crystallization of monomers, chains and dimers
Résumé
Five new chiral MnIII complexes [Mn((1R, 2R)-Salcy)N3]∞⋅CH3CN (1), [Mn((R,R)-Salcy)N3]∞ (2), [Mn((R,R)-Salcy)N3] (4), [Mn((R,R)-Salcy)(H2O)N3]⋅C4H8O (5) and [Mn((R,R)-Salcy)NCS] (6) have been synthesized and characterized by X-ray structural analysis and magnetic measurements (Salcy=N,N′-bis(salicylidene)-1,2-diaminocyclohexane. The four azido complexes have been obtained from the previously known [Mn((R,R)-Salcy)(CH3OH)N3] (3) by crystallization from various solvents. Compounds 1 and 2 are trans-μ-1,3-azide bridged coordination polymers. While 1 forms helical chains, the chain in 2 is formed via translation of a dimeric helicate repeat unit. Compound 3 is a methanol coordinated mononuclear azido complex which forms a 2D-network through H-bonding. Compounds 4 and 6 are phenoxo-bridged dimers without inversion center. Compound 5 is an aqua coordinated mononuclear azido complex, which forms a 1D-chain through O−H⋅⋅⋅N hydrogen bonding involving axial ligands. In all six compounds MnIII exhibits a characteristic Jahn−Teller elongation. The magnetic coupling in 1 and 2 leads to antiferromagnetic interaction along the chain (2 J=−11.6 cm−1 for 1 and –11.9 cm−1 for 2) through the μ-1,3-azide bridge. Compound 3 is weakly antiferromagnetic due to hydrogen bonding interactions in the lattice. The phenoxo dimers (4 and 6) do not have measurable exchange interaction, the low temperature susceptibility being influenced mainly by zero-field splitting.