Halogen–halogen interactions and halogen bonding in thiacalixarene systems

Abstract

Crystals of 5,11,17,23-tetraiodo-25,26,27,28-tetrapropoxythiacalix[4]arene (2) exhibited I⋯I halogen–halogen interactions between each of the thiacalixarene molecules, the distance of which is ca. 2% shorter than the sum of the respective van der Waals atomic radii. Further support for S–π and C–H⋯I interactions and hydrogen bonding was provided by the formation and characterization of a three-dimensional supramolecular assembly of 2via preferential intermolecular I⋯I interactions. In contrast, crystals of 5,11,17,23-tetraiodo-25,26,27,28-tetrabutoxythiacalix[4]arene (3) were identified to have S⋯I halogen bonds that are ca. 4.5% shorter than the sum of the respective van der Waals atomic radii. The extended structure of 3 also formed a three-dimensional supramolecular assembly exhibiting S⋯I halogen bonding and hydrogen bonding, in addition to ancillary S–π and C–H⋯I interactions. We have also elucidated I⋯I and S⋯I interactions by computational approaches.