|Name||Mr. Will Henderson|
|Organization or Institution||University of Florida|
EXPANDING THE FAMILY OF SELF-ASSEMBLING PARACYCLOPHANES
Will R. Henderson, Danielle E. Fagnani, Yu Zhu, Guancen Liu, and Ronald K. Castellano
University of Florida
Paracyclophanes are an exciting class of macrocyclic molecules possessing one or more aromatic rings incorporated into a larger ring system. The most well-studied of these molecules is [2.2]paracyclophane. Since its discovery, it has fascinated chemists including Nobel laureate Donald J. Cram. Its unique properties, including non-planar aromaticity, planar chirality, and potential for through-space conjugation remain attractive. [2.2]paracyclophane however, is not well studied in the realm of supramolecular chemistry. We sought to make use of the rigid nature of the paracyclophane skeleton, to create a supramolecular polymer that would self-assemble through intra- and intermolecular amide hydrogen bonding. The molecular building block which fulfilled the original design was [2.2]paracyclophane -tetracarboxamide ([2.2]pCpTA). The synthesis and characterization of the [2.2]pCpTA supramolecular polymer led to more questions about the role of the intramolecular amide hydrogen bond as well as the rigidity of the [2.2]paracyclophane skeleton in the assembly process. To address the intramolecular hydrogen bond we recently synthesized comparator molecules including [2.2]paracyclophane diamide regioisomers. Their study allowed us to conclude that the intramolecular hydrogen bond is necessary for the preorganization of the amide groups for intermolecular hydrogen bonding. [2.2]Paracyclophane possesses some 31.6 kcal/mol of strain energy, but its three-carbon bridge homolog [3.3]paracyclophane boasts only 11 kcal/mol of strain energy. By synthesizing the [3.3]paracyclophane variant of our original system([3.3]pCpTA), the effect of ring strain and dynamics on self-assembly could be revealed. The synthesis and preliminary investigation of [3.3]pCpTA will be presented.