Photo-reactions of molecules with two [2π + 2π]-cycloaddition sites in the solid state are reported. Four thyminyl stilbazoles having both a stilbazole olefin and a thyminyl olefin were synthesized using the Heck reaction of halo-pyridine substrates with vinylbenzyl thymine or methylated vinylbenzylthymine. Only one of them, methylated vinylbenzylthymine with 4-pyridine, was photoreactive and formed a head-to-tail stilbazole dimer. The crystal structures of thyminyl stilbazoles and the stilbazole dimer were used to investigate the structure-reactivity relationships.