UV photoelectron spectra, reduction potentials and MO calculations of intramolecularly hydrogen-bonded naphtoquinones

¹ Dipartimento di Scienze Chimiche, Università di Catania, Viale A Doria 8, 95125 Catania, Italy
² Istituto di Chimica dell'Università della Basilicata, 85100 Potenza, Italy

Abstract

Ionization and reduction potentials of 1,4-naphtoquinone, 4- and 2-hydroxynaphtoquinones and their corresponding methoxy derivatives have been measured by gas phase U.V. photoelectron spectroscopy and a.c. voltammetry in acetonitrile solutions. Experimental findings were compared with the results of theoretical calculations by employing semiempirical, ab initio and DV-Xα methods. Intramolecular hydrogen bonds stabilize the n- and n+ orbital energies and lead to enhanced electron affinities. The photoelectron spectra are satisfactorily reproduced by the HAM/3 and DV-Xα calculations. HAM/3 and MNDO methods are the more successful in reproducing quantitatively changes in the solution electron affinities.