The effect of electron withdrawing ligands on the energy barriers of Single-Molecule Magnets (SMMs) is investigated. By introducing highly electron withdrawing atoms on targeted ligands the energy barrier was significantly enhanced. The structural and magnetic properties of five novel SMMs based on a dinuclear {Dy2} phenoxo-bridged motif are explored and compared with a previously studied {Dy2} SMM (1). All complexes share the formula [Dy2(valdien)2(L)2]•Solvent where H2valdien = N1,N3-bis(3- methoxysalicylidene) diethylenetriamine, the terminal ligand L = NO3 - (1), CH3COO- (2), ClCH2COO- (3), Cl2CHCOO- (4), CH3COCHCOCH3 - (5), CF3COCHCOCF3 - (6) and Solvent = 0.5 MeOH (4), 2 CH2Cl2 (5). Systematic increase of the barrier was observed for all complexes with the most drastic increase seen in 6 when the acac ligand of 5 was fluorinated resulting in a 7-fold enhancement of the anisotropic barrier. Ab initio calculations reveal more axial g-tensors as well as higher energy first excited Kramers doublets in 4 and 6 leading to higher energy barriers for those complexes.