For the purpose of engineering magnetic anisotropy, chiral binaphthyl substituents with slight electron-withdrawing ability and dibutylamino substituents with intense electron-donating nature are incoporated onto the periphery of each phthalocyanine ligand in the bis(phthalocyaninato) terbium double-decker compound, resulting in the chiral heteroleptic bis(phthalocyaninato) terbium complex (R)/(S)-[Pc(OBNP)(4)]Tb{Pc[N(C4H9)(2)](8)} (R/S-1) {Pc(OBNP)(4) = {tetrakis(dinaphtho[1,2-e:1,2-g]-1,4-dioxocine)[2,3-b;2,3-k;2,3-t;2,3-c]phthalocyanine}; Pc[N(C4H9)(2)](8) = [2,3,9,10,16,17,23,24-octakis(dibutylamino)phthalocyanine]}. Magnetic studies reveal the typical single-ion magnet (SIM) nature of this chiral bis(phthalocyaninato) terbium double-decker with spin reversal energy barrier of 638 K. A butterfly-shaped magnetic hysteresis loop was observed at even 25 K for R-1 under the sweep rate of 500 Oe s(-1). The performance of this SIM is well rationalized on the basis of theoretical analysis of the electrostatic potential according to calculations using the density functional theory method.