2:1 Complex of 4-methylphenol with piperazine, structure in the solid and solution state

Abstract

The title complex has been obtained from the solution of 4-methylphenol and piperazine, and the crystal structure has been determined by X-ray diffraction analysis. The complex crystallizes in space group P-1, each piperazine molecule linking two 4-methylphenol molecules via H-bonding between the amine N atoms and the phenol hydroxyl group. 1H NMR spectra indicate that the complex formed with the aid of H-bonding exists also in the solution. The proton peaks assigned to the hydroxyl and amine groups in pure 4-methylphenol and piperazine merge into one in the title complex, which implies that the H-bond between the hydroxyl O and the amine N atoms is involved in a fast proton exchange process. The ESI-MS spectrum of the solution of the title complex also provides evidence for the existence of the 2:1 complex in the solution.