π−π Interactions and Solid State Packing Trends of Polycyclic Aromatic Bowls in the Indenocorannulene Family: Predicting Potentially Useful Bulk Properties

Abstract

Solid state crystal structures are discussed and compared for all seven members of the indenocorannulene family that have been recently synthesized by iterative microwave-assisted intramolecular arylations and characterized by single crystal X-ray diffraction. These bowl-shaped polyaromatic hydrocarbons include monoindenocorannulene (C26H12), two isomers each of diindenocorannulene (C32H14) and triindenocorannulene (C38H16), tetraindenocorannulene (C44H18), and pentaindenocorannulene (C50H20), with all molecules mapping onto the geodesic framework of the C60-fullerene. This extended family of π-bowls represents a unique case of a stepwise build-up of size, curvature, and strain at the corannulene core. It allows the first evaluation of the effects of controlled extension of nonplanar π-aromatic surfaces on the solid state structures of the resulting crystalline solids. First, a face-to-face π−π alignment of individual bowls to form 1D stacks is considered and compared for all the above indenocorannulenes having different numbers and different positioning of indeno-groups fused to the corannulene core. Second, the orientations of these 1D columns with respect to each other and their secondary interactions are analyzed. Interesting packing trends and crystal structure variations are found as the size and the curvature of the π-bowls increase. These large π-conjugated carbon-rich systems constitute promising new materials for applications in molecular electronics, with the key to unlocking their specific and unique properties lying in the solid state packing and intermolecular interactions of the individual π-bowls. A thorough analysis of the crystalline structures of the indenocorannulene family, augmented by DFT calculations, has allowed the first predictions of their bulk materials properties.