Photogeneration of an ADADA H-bonding cleft based on a naphthopyran-decorated triazine

Bis-capped DAD H-bonding triazine units have been designed and synthesized, the two masking building blocks being 3,3-diphenyl-3H-naphtho[2,1-b]pyrans. Upon photoirradiation, the ring opening of both photochromic units leads to the formation of a five ADADA H-bonding site molecule. The conversion between the closed, mono-open and bi-open forms has been elucidated using NMR technique which has allowed to assign the corresponding rotamers and isomers, and their relative abundance. No self-aggregation has been observed for the closed form but more importantly also for the photogenerated structures.