We report the synthesis, structures, and magnetic properties of two novel linear tetranuclear complexes with the general formula [Dy4(Hheb)2(heb)4X2(MeOH)4] (X- = NO3-, OAc-; H2heb = (E)-N'-(1-(2-hydroxyphenyl)ethylidene)benzohydrazide, OAc- = acetate). The rigid ligands (Hheb-/heb2-) incorporate phenoxide groups and bridge the Dy3+ ions in an unusual tetranuclear linear assembly. Notably, we demonstrate through magnetic measurements and theoretical calculations how the anion (X) coordinated at the peripheral Dy3+ centers acts as a switch, significantly changing the magnetic anisotropy of the entire complex. This control over magnetic anisotropy through the selection of the coordinated anion offers a promising avenue for tailoring the functionality of single-molecule magnets.