A non-rotatory isomerization path in ethene derivatives? Investigation of a stilbenophane and protonated azobenzenophanes (pseudo-stilbenophanes)

A stilbenophane and protonated azobenzenophanes (pseudo-stilbenes) with four -CH2-S-CH2- bridges in all meta-positions were synthesized. The spectroscopic and photochemical properties were investigated: excited dimer absorption spectra and for the stilbenophane also emission spectra were observed. Photochemical reactions could be identified as the [2+2] photocycloaddition for the stilbenophane; the nature of the photoproducts in the case of pseudo-stilbenes could not be established. Photo-isomerizations could not be observed which gives a negative answer to the title question.