The sequential reaction of 2-((6-(hydroxymethyl)pyridin-2-yl)-methyleneamino)phenol (LH2), LnCl(3)center dot 6H(2)O, and 1,1,1-trifluoroacetylacetone (Htfa) in the presence of Et3N afforded [Ln(LH) (tfa)(2)] [Ln = Dy3+ (1), Ln = Tb3+ (2), and Ln = Gd3+ (3)], while under the same reaction conditions, but in the absence of the coligand, another series of mononuclear complexes, namely, [Ln(LH)(2)]-Cl center dot 2MeOH] [Ln = Dy3+ (4) and Tb3+ (5)] are obtained. Singlecrystal X-ray diffraction analysis revealed that the former set contains a mono-deprotonated [LH](-) and two tfa ligands, while the latter set comprises of two mono-deprotonated [LH](-) ligands that are nearly perpendicular to each other at an angle of 86.9 degrees. Among these complexes, 2 exhibited a ligand-sensitized lanthanide-characteristic emission. Analyses of the alternating current susceptibility measurements reveal the presence of single-molecule magnet behavior for 1 and 4, in the presence of direct-current field, with effective energy barriers of 4.6 and 44.4 K, respectively. The enhancement of the effective energy barrier of the latter can be attributed to the presence of a large energy gap between the ground and first excited Kramers doublets, triggered by the change in coordination environments around the lanthanide centers.