Self-Assembled Thermally Highly Stable 1-Dimensional Proton Arrays

From a red proton complex of aldehyde derivatives of polyaromatic hydrocarbon with strong intermolecular hydrogen bonding, which are novel examples of intermolecular proton-bonded aldehydes of polyaromatic hydrocarbons, we find one-dimensional proton arrangement. The complex formed as 9-antraldehyde (Ant-CHO) reacts with HAuCl4 to form [(Ant-CHO)2H]+[AuCl4]− under dry condition, which are confirmed by single-crystal structure determination and infrared spectra analysis at varying temperatures. Since the compounds of distinctively hydrophobic nature are soluble only in limited organic polar solvents, the strong hydrogen bonds are clearly observed from both the electron density of X-ray analysis and the characteristic signature of the IR frequency. The proton complex units have the typical O−H+−O distance of the strong hydrogen bond similar to the Zundel-like cationic hydrogen bond (where two O atoms share a proton in the midpoint of the short O−O distance of ∼2.4 Å). The chemical shift of 20.18 ppm originated from the protons of the O−H+−O hydrogen bonds would be the largest downfield shifted value among those of protons in O−H···O bonds reported in various solid materials, indicating very short strong hydrogen bonds for the O−H+−O. The complexes are stabilized with the π−π intermolecular interactions of the polyaromatic hydrocarbon ligands, resulting in layered structures. The spectral signatures around ∼900, ∼1200, and ∼1700 cm−1 for the Zundel-like proton bond are clearly characterized.