Influence of weaker interactions on the self-assembly of rigid molecular scaffolds based on tetraarylbimesityls

We have explored how weak interactions would manifest in three-dimensional (3D) rigid scaffolds based on tetrarylbimesityls in which the close packing is likely to be more decisive. While the crystal structure of tetrapyridyl bimesityl (3,3',5,5'-tetrakis(4-pyridyl)bimesityl, 2) is found to be a close-packed one devoid of any perceptible interactions, that of 3,3',5,5'-tetrakis(3-pyridyl)bimesityl (1) is found to reveal a novel ring motif based on C-H···N hydrogen bonds, which serves to organize the molecules into a cubic α-Po-like network. The cyano-substituted derivative (3,3',5,5'-tetrakis(4-cyanophenyl)bimesityl, 3) is found to exhibit a helical organization as a result of C-H···N interactions and electrophile-nucleophile type pairing. Evidently, the interactions due to groups that interact weakly appear to be exploited in the crystal packing of 3D scaffolds only when their existence can be accommodated by a molecular packing that leads to overall crystal lattice stabilization as in 1 and 3. The crystal structures of 1 and 2 suggest a strong dependence on the location of weakly interacting sites. In the crystal structures of 3D rigid scaffolds, the close packing appears to dictate the manifestation or otherwise of the weak interactions and their association patterns/motifs