Molecular structure and infrared spectra of 2-hydroxy-1,4-naphthoquinone; Experimental matrix isolation and theoretical Hartree-Fock and post Hartree-Fock study

The infrared spectra of 2-hydroxy-1,4-naphthoquinone (HNQ) isolated in low-temperature Ar and N-2 matrices are reported. The calculations of electronic energies for possible tautomers of HNQ (performed at RHF/6-31 + + G** and MP2/6-31 + + G** levels of theory) and the comparison of the experimental spectra with those theoretically calculated (at the RHF/6-31 + + G** and DFT(B3-LYP)/6-31 + + G** levels) show that the molecules of the compound isolated in low-temperature matrices exist in the form with intramolecular hydrogen bond. Theoretical results reproduce well the experimental infrared spectra of the matrix isolated HNQ. The assignment of the infrared absorption bands due to monomers of the compound isolated in Ar and N-2 matrices to the theoretically predicted normal modes is presented. (C) 1998 Elsevier Science B.V. All rights reserved.