Three novel mononuclear lanthanide complexes coordinated with 1-methylimidazole [Ln(hfac)₃·(1-MeIm)₂] (Ln = Dy(1), Tb(2) and Ho(3), hfac = hexafluoroacetylacetonate, 1-MeIm = 1-methylimidazole) have been designed and characterized by single-crystal X-ray diffraction, luminescence and magnetic measurements. Studies indicate that the metal ions of all three mononuclear complexes adopt a slightly distorted D_4d [LnO₆N₂] coordination environment, which is formed by two terminal 1-methylimidazole ligands and three bischelating hfac⁻ anions. Frequency dependent out-of-phase signals were observed for complex 1 in dynamic magnetic susceptibility measurements, which indicates single-molecule magnetic behavior.