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

The title complex has been obtained from the solution of 4-methylphenol and piperazine, and the crystal structure has been determined by X-ray diffrac tion analysis. The complex crystallizes in space group P-l, each piperazine molecule linking two 4-methylphenol molecules via H-bonding between the am ine N atoms and the phenol hydroxyl group. H-1 NMR spectra indicate that th e 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-methylphe nol 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 fa st proton exchange process. The ESI-MS spectrum of the solution of the titl e complex also provides evidence for the existence of the 2:1 complex in th e solution. (C) 2001 Elsevier Science B.V. All rights reserved.