For the purpose of further exploring the effect of nonperipherally attached substituents on single-ion magnet (SIMs) performance, tetrasubstituted bis[1,8,15,22-tetrakis(3-pentyloxy)-phthalocyaninato]terbium double-deckers, in both the reduced form TbH[Pc(alpha-OC5H11)(4)](2) (1) and the neutral form Tb[Pc(alpha-OC5H11)(4)](2) (2) were prepared. Single-crystal X-ray diffraction analysis for 2 unambiguously demonstrates the pinwheellike molecular structure with C-4 symmetry. Magnetic investigations of the two bis(phthalocyaninato)terbiumdouble-deckers reveal their characteristic SIM nature. 2 exhibits SIM performance superior to that of 1, as revealed by the larger energy barrier of 466 K for the former species and 431 K for the latter species due to the presence of organic radical-f (radical Tb) interactions. The enhanced SIM performance of 2 in comparison to 1 actually stems from the presence of radical-f interactions and an enhanced ligand field strength. The latter positive factor is indicated by the electrostatic potential around the terbium ion on the basis of density functional theory (DFT) calculations.