Supporting Information for: Photo-Triggered Self-Assembly of Hydrogen-Bonded Rosette Shiki Yagai,* Toshiharu Nakajima, Takashi Karatsu, Akihide Kitamura Department of Materials Technology, Faculty of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. Synthesis. Scheme S1 outlines the synthesis of melamine−azobenzene−TDP conjugate M2 and barbituric acid−TDP conjugate B2. Melamine M2 was prepared starting from the reaction of 4-hydroxy-4'-nitroazobenzene (1) 1 with 3,4,5-tri(n-dodecan-1-yloxy)benzyl chloride 2 in a standard etherification condition. Selective reduction of the nitro group of the resulting 2 was accomplished by Na 2 S in water-dioxane mixtures to afford the corresponding amino derivative 3 in moderate yield (74 %). Introduction of the aminoazobenzene-TDP conjugate 3 into triazine functionality was done according to the literature. 3 Namely, cyanuric trichloride was treated with 2 equiv. of 3 to give 4, which was subsequently treated with a mixture of aqueous ammonia and dioxane at 117 °C to give M2. Due to the low nucleophilicity of the amino group of azobenzene derivative 3, the former reaction was done in relatively high temperature (reflux in THF) as compared to standard conditions (room temperature). Another target compound, merocyanine type barbiturate B2, were prepared via the reaction of tris(n-dodecan-1-yloxy)benzaldehyde 5 2 with barbituric acid according to the literature procedures. 4