The relationship between aromaticity and hydrogen bonding in the self-assembly of a supramolecular polymer is examined. Partially aromatic bis(squaramide) bolaamphiphiles were designed to self-assemble through a combination of hydrophobic, hydrogen-bonding and aromatic effects into long fibrillar architectures. Electronic and geometric changes within the squaramide ring indicative of strong hydrogen bonding and aromatic gain of the monomer units were observed using IR and UV-vis spectroscopy. Greater aromatic character upon polymerization, at least 30 percent of the interaction energy in a pentamer, was determined computationally using nucleus-independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) indices. A significant increase in thermodynamic stability and a striking difference in the morphology of the self-assembled bis(squaramide) bolamphiphiles was observed in comparison to isosteres that cannot access the aromatic gain-hydrogen bonding effect.

Synergy between aromatic gain and hydrogen-bonding in a supramolecular polymer

251st National Meeting (2016)

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