Concomitant Photochemical and Phase Rearrangements 2. Luminescent and X-Ray Studies on Photochemistry of Cis- and Trans-1,2-Di-(1 -Naphthyl)ethylenes in the Crystalline State

Abstract It is shown that topochemically controlled cis-trans-photoisomerization in crystals of cis-DNE 2-5 μm in size occurs without single crystal destruction. The energy of the newly formed trans-crystal structure is lowered by ca. 5.6 kcal · mole−1. In larger monocrystals the isornerization is accompanied by sample cracking. Photolysis of trans-crystals in the presence of oxygen results in photocyclization and picene formation. The concomitant dimerization and cyclization reactions are not observed in crystalline cis- and trans-DNE which was accounted for by the particular features of the crystal lattice.