An alternating-current (ac) magnetic susceptibility measurement for the [(Pc)(2)Tb-III](0) complex (Pc = phthalocyaninato) has shown that ligand oxidation of the anionic [(Pc)(2)Tb-III](-) complex gives rise to a significant upward shift of the temperature range where the magnetization response shows a phase lag behind the time-varying external magnetic field. The peaks of the out-of-phase component of the ac susceptibility of the pi-radical [(Pc)(2)Tb-III](0) were observed at 50, 43, and 36 K with ac magnetic fields of 10(3), 10(2), and 10 Hz, respectively, which were more than 10 K higher than the corresponding values of the anionic complex with a closed-shell.7r-system. The ac susceptibility measurements on the complex with octa(dodecoxy) -substituted Pc ligand, which is readily dilutable in diamagnetic media, proved that the significant rise of the temperatures occurs as an intrinsic single-molecular property of the complex possessing both J = 6 and S = (1)/(2) systems, and is not due to long-range magnetic order or interactions between adjacent unpaired pi-electrons.