Photophysics and photochemistry of naphthoylnaphthvalene, and photoinduced valence isomerization of highly strained aromatic compounds (Or Quinones) yielding the valene-type isomers as well as related photochromism and photo-electro dualchromism

The lowest excited singlet state of naphthoylnaphthvalene (NNV) undergoes valence isomerization yielding ground-state naphthoylnaphthalene (NN) finally. Neither the lowest excited singlet nor triplet state of NN is formed upon excitation of NNV, and of particular interest in photoinduced NNV→NNV valence isomerization is the existence of an intermediate which is probably either a bond-cloven species or a valence isomer of NNV. The lowest excited triplet state of NNV populated in benzene deactivates to its ground state, but that populated in ethanol abstracts a hydrogen atom from the solvent molecule generating the NNV ketyl radical. Interestingly, this radical also undergoes rapid valence isomerization and recombination of two NN ketyl radicals thus formed yields naphthopinacol. Synthesis of poly-tert-butylpolyacenes, tri-tert-butylisobenzofuran and tri-tert-butylpolyacenequinones, and furthermore, their photoinduced valence isomerization yielding the valene-type isomers as well as related photochromism and photo-electro dualchromism are presented.