Trans - and cis -1, 2-bis (3-aminophenyl)-1, 2-diphenylethens, tr -3DA and cs -3DA, were synthesized via four steps and isolated using a middle pressure liquid chromatograph. The structures were elucidated by NMR and the absolute configurations were determined by single crystal X-ray structure analysis. The tr -3DA and the cs -3DA molecules possess four twisted benzene rings like a propeller and have many itropisomers. They underwent an isomerization reaction each other under light irradiation.