Novel photochromic spiroheterocyclic molecules via oxidation of 1,8-diaminonaphthalene

[reaction: see text] Novel spiroheterocyclic molecules, namely, 2,3-dihydro-2-spiro-7'-[8'-imino-7',8'-dihydronaphthalen-1'-amine]perimidine, PNI, and 2,3-dihydro-2-spiro-4'-[8'-aminonaphthalen-1'(4H)-one]perimidine, PNO-p, were obtained by oxidation of 1,8-diaminonaphthalene using manganese dioxide. These molecules exhibit thermally reversible photochromism with good photofatigue resistance, and their photogenerated forms possess broad absorption in the visible region.