Photochromic Properties of Spiro[fluorene-chromenes]

Two annelated spiro[fluorene-chromene] structures, spiro[2H-benzo[h]chromene-2,9'-fluorene], C₂₅H₁₆O, and 9,10,11,12-tetrahydrospiro[3H,8H-cyclohepta[4,5]furano[3,2-f]chromene-2,9'-fluorene], C₂₈H₂₂O₂, have been analysed in order to define the effect of introducing a spiro-C atom into the pyran ring on the photochromic properties of the chromenes. The results are compared with those obtained for previously studied non-spiro 2,2-substituted chromenes.

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