Photophysics and photochemistry of naphthoylnaphthvalene, and photo-induced valence isomerization of highly strained aromatic compounds (or quinones)yielding the valene-type isomers as well as related photo-chromism and photo-electro dual-chromism

The lowest excited singlet state of naphthoylnaphthvalene (NNV) undergoes v alence isomerization yielding ground-state naphthoylnaphthalene (NN) finall y. Neither the lowest excited singlet nor triplet state of NN is formed upo n excitation of NNV, and of particular interest in photoinduced NNV-->NNV v alence 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 m olecule generating the NNV ketyl radical. Interestingly, this radical also undergoes rapid valence isomerization and recombination of two NN ketyl rad icals thus formed yields naphthopinacol. Synthesis of poly-tert-butylpolyac enes, tri-tert-butylisobenzofuran and tri-tert-butylpolyacenequinones, and furthermore, their photoinduced valence isomerization yielding the valene-t ype isomers as well as related photochromism and photo-electro dualchromism are presented.