Photoisomerization of a fullerene dimer

A photo-switchable fullerene dimer and its analogous nitrogen endohedral species have been synthesized and characterized. Irradiation by ultraviolet and visible light has been used to switch between the trans and cis isomers of both the C60- and N@C60- based dimers. Environmental perturbations experienced by the encapsulated nitrogen atom upon switching between the two isomers in degassed carbon disulfide has been determined by pulse electron paramagnetic resonance. Both T1 and T2 electron spin relaxation times of the two isomers of the endohedral fullerene containing dimer revealed a biexponential decay. Although the zero field splitting parameter Deff for both isomers in solution was similar, around 13.0 MHz, the molecular rotation correlation time τC of the trans and cis isomers was calculated to be 37.2 ± 1.6 and 34.8 ± 2.7 ps, respectively. © 2008 American Chemical Society.