NEW PHOTOCHROMIC BIS-SPIROCYCLIC SYSTEMS

Novel photochromic bis-spirocyclic compounds, derivatives of di(4-cycl ohexa-2,5-dien-1-one)benzimidazole 5a and di(4-cyclohexa-2,5-dien-1-on e)perimidine 8a have been synthesized. Under UV-irradiation of their t ol;ene solutions compounds 5a (lambda(max) = 474 - 502 nm) undergo the rmally irreversible rearrangement to the isomeric bis-quinoneimines 5b (lambda(max) = 593 - 602 nm). When treated with trifluoroacetic acid in toluene 5a and 8a form monoprotonated cations 5aH(+) and 8aH(+)(lam bda(max)=375 - 384 nm) which reveal photocromic properties. The photoi somers of the cations 5aH(+) and 8aH(+) possess long-wave absorption b ands properties (lambda(max)=766 - 810 nm). Quantum yields fall into t he range of 0.13-0.17.