Photochromism of a naphthalene-bridged imidazole dimer constrained to the "anti" conformation.

Anti-1,8-bisTPI-naphthalene in which two imidazole rings are constrained to an anti-conformation leading to the first-formed 1,4'-isomer of the bridged imidazole dimer has been synthesized. The color of the radicals is different from that of the previously reported bridged-imidazolyl radicals because the intramolecular interaction between the radicals becomes weak due to the anti-conformation. This molecular design would be a profitable strategy to control the color of the radicals of the bridged imidazole dimer for application in ophthalmic lenses.