Photoisomerization of cis,cis-1,4-diphenyl-1,3-butadiene in glassy media at 77 K:: the bicycle-pedal mechanism

The cis-trans photoisomerization of cis,cis-1,4-diphenyl-1,3-butadiene in a soft isopentane glass at 77 K gives significant two-bond photoisomerization in contrast to solution and hard glassy media where only one-bond photoisomerization takes place.