Helicity and Topological Chirality in Hydrogen-Bonded Supermolecules Characterized by Advanced Graph Set Analysis and Solid-State Vibrational Circular Dichroism Spectroscopy

The applicability of advanced graph set analysis and solid-state vibrational circular dichroism (SD-VCD) spectroscopy to the characterization of supramolecular chirality has been demonstrated. Recrystallization of R-(+)-1-phenylethylammonium 1-naphthoate affords two polymorphic crystals: one is composed of hydrogen-bonded (HB) 2-fold helices with helicity, while the other contains HB clusters with topological chirality. Handedness and origins of the chirality were crystallographically characterized by advanced graph set analysis. SD-VCD measurements were then recorded for these polymorphic crystals using the VCD spectrometer PRESTO-S-2007, which we developed. Unique VCD spectra were observed because of the difference in features of the chiral supramolecular structures. Enhancement of VCD signals depending on dimensionality of the supermolecules is especially noteworthy. Generality of 2-fold helices, demonstrated by statistics from the Cambridge Structural Database, and geometrical characteristics and theoretical simplicity of the HB clusters, because of their finite number of components connected by closed-hydrogen bonding networks, allowed them to become reasonable representative examples for chiral supermolecules.