Squarephaneic Tetraanhydride: A Conjugated Square-Shaped Cyclophane for the Synthesis of Porous Organic Materials

Aromatic carboxylic anhydrides are ubiquitous building blocks in organic materials chemistry. In particular, dianhydrides and their conversion into imides have received considerable attention in the synthesis of organic semiconductors, pigments, and battery electrode materials. Here we extend the family of aromatic carboxylic anhydrides with a unique new member, a conjugated cyclophane with four anhydride groups. The cyclophane, named squarephaneic tetraanhydride due to its square shape, is obtained in a three-step synthesis; the anhydride groups are located at the corners and allow for efficient functionalisation, as shown by the conversion into imides and carboxylates. The crystal structures of the tetraanhydride and one of the imides demonstrate the high degree of porosity achievable with the new building block. Electrochemical measurements in solution and solid state are also presented. Considering the short synthesis and unique properties, we expect widespread use of the new building block in the development of organic materials.