Hydrogen-bonding interactions between 1-methylindole and alcohols

A theoretical and experimental FTIR study has been undertaken to analyse the pi-hydrogen-bonding interactions between 1-methylindole (1MI), and the alcohols trifluoroethanol, and hexafluoroisopropanol. Experimental IR measurements performed on the OH stretching band of the alcohols, in hexane as solvent, showed that, after the addition of 1MI, a composite associated red-shifted band is formed. Ab initio calculations (DFT/B3LYP) performed with different starting geometries and stoichiometries led us to propose the initial formation of 1:1 T-shape OH-pi hydrogen-bonded complexes which, furtherly, are stabilised by hydrogen-bonding interaction with a second alcohol molecule, giving ternary 1:2 complexes. (C) 2004 Elsevier B.V. All rights reserved.