Low-melting cationic 3d-transition metal complexes of azole-based ligands

Ligands N-methylimidazole (MIm) and N-ethylimidazole (EIm) were used for the preparation of [FeII(L)6](NTf2)2·0.5EtOH·0.5H2O. With Tfus = 83 °C, the EIm complex was characterised as paramagnetic MeIL. Using bidentate imidazole ligands 2-(2-pyridyl)-1-ethylimidazole (L1) and 2-(2-pyridyl)-1-(2-methoxyethyl)imidazole (L2) 3:1 type complexes [MII(Li)3]X2 (M = Fe; Li = L1; X = ClO4, BF4, NTf2; M = Fe; Li = L2, X = ClO4, BF4; M = Co; X = ClO4; Li = L1, L2; M = Ni; X = ClO4; Li = L1, L2) were prepared. All complexes of L2 and complex [FeII(L1)3](NTf2)2 were low-melting with Tfus < 200 °C. Complexes of L2 additionally had glass transition temperatures below 75 °C upon reheating.

Even L1 [2-(2-pyridyl)-1-ethylimidazole] with the relatively short ethyl tag, in combination with NTf2−, is able to form low-melting complexes. Also most complexes of the methoxyethyl-tagged ligand L2 [2-(2-pyridyl-1-(2-methoxyethyl)imidazole] are low-melting with Tfus < 200 °C and have glass transitions below 75 °C upon reheating.Figure optionsDownload as PowerPoint slide