The present work reports a new mononuclear Dy(III) complex [Dy(acac)₃(dppn)]·C₂H₅OH (1) (acac = acetylacetone, dppn = benzo[i]dipyrido-[3, 2-a:2′,3′-c]phenazine). X-ray crystallography analysis reveals that compound 1 is a discrete molecular complex and the Dy(III) center lies in a square-antiprism coordination environment. Furthermore, complex 1 shows single-ion magnet (SIM) behavior. Compared to the reported complexes [Dy(dppz)(acac)₃]·CH₃OH, [Dy(dpq)(acac)₃] and [Dy(phen)(acac)₃], complex 1 exhibits a different energy barrier, which might be raised from the different coordination environment caused by the different auxiliary co-ligand dppn. The energy barrier variations of these Dy(III)-complexes are consistent with their square antiprism structural features.