Aromatic embedding wins over classical hydrogen bonding - a multi-spectroscopic approach for the diphenyl ether-methanol complex

Dispersion interactions are omnipresent in intermolecular interactions, but their respective contributions are difficult to predict. Aromatic ethers offer competing docking sites for alcohols: the ether oxygen as a well known hydrogen bond acceptor, but also the aromatic pi system. The interaction with two aromatic moieties in diphenyl ether can tip the balance towards pi binding. We use a multi-spectroscopic approach to study the molecular recognition, the structure and internal dynamics of the diphenyl ether-methanol complex, employing infrared, infrared-ultraviolet and microwave spectroscopy. We find that the conformer with the hydroxy group of the alcohol binding to one aromatic pi cloud and being coordinated by an aromatic C-H bond of the other phenyl group is preferred. Depending on the expansion conditions in the supersonic jet, we observe a second conformer, which exhibits a hydrogen bond to the ether oxygen and is higher in energy.