C59N magnetic fullerenes were formed inside single-wall carbon nanotubes by vacuum annealing functionalized C59N molecules encapsulated inside the tubes. A hindered, anisotropic rotation of C59N was deduced from the temperature dependence of the electron spin resonance spectra near room temperature. Shortening of the spin-lattice relaxation time T-1 of C59N indicates a reversible charge transfer toward the host nanotubes above similar to 350 K. Bound C59N-C-60 heterodimers are formed at lower temperatures when C-60 is coencapsulated with the functionalized C59N. In the 10-300 K range, T-1 of the heterodimer shows a relaxation dominated by the conduction electrons on the nanotubes.