Cavitand and Flexible Amphiphilic Resorcin[4]arenes: Structural Characterization and Supramolecular Interactions in Crystal Networks

Crystal structures of two resorcinarene units, namely, a cavitand type upper periphery in which the upper rims are functionalized with hydroxyl groups (RCOH4) and a similarly substituted resorcinarene analogue with non-rigid and flexible upper portion (ROOH4)-are discussed. The functionalization is symmetrical with all of the four upper rim positions being derivatized. The molecular structure of RCOH4 obtained from single crystal diffraction is consistent with the cone conformation, whereas that of ROOH4 possesses a boat conformation at the head position. The boat conformation of ROOH4 is further confirmed by low temperature NMR analysis. The presence of four OH functional groups in the head position enable these resorcinarene units to form efficient H-bonds with neighboring resorcinarene moieties or solvent molecules. The alkyl groups at the tail portions are also involved in C-H center dot center dot center dot C or C-H center dot center dot center dot O type weak hydrophobic intermolecular interactions. Hirshfeld surface analysis mapped with dnorm plots and the related 2D fingerprint diagrams also indicate the presence of H center dot center dot center dot O and H center dot center dot center dot C intermolecular interactions within these crystals. The supramolecular interactions in RCOH4 have resulted in an ordered bilayer type of packing with separated polar and non-polar parts in its crystal. However, the packing pattern in the ROOH4 crystals is quite different from that of RCOH4 in which each row is aligned with resorcinarenes of alternating upper and lower rims. [GRAPHICS] .

Automated summary

The crystal structures of two resorcinarene units, RCOH4 and ROOH4, with different functional groups at their upper rims are discussed. The presence of hydroxyl groups allows for efficient hydrogen bonding interactions, while alkyl groups participate in weak hydrophobic interactions. The supramolecular interactions in RCOH4 result in an ordered bilayer packing, while ROOH4 crystals have a different packing pattern with alternating upper and lower rim alignment.