Matrix Isolation Infrared Spectroscopic and Theoretical Study of the Interaction of Water with Dimethyl Methylphosphonate

Authors

Bruce S. Ault, Department of Chemistry, UniVersity of Cincinnati, P.O. Box 210172, Cincinnati, Ohio
Alex Balboa, Edgewood Chemical Biological Center, Aberdeen ProVing Ground, Maryland
David Tevault, Edgewood Chemical Biological Center, Aberdeen ProVing Ground, Maryland
Margaret Hurley, Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen ProVing Ground, Maryland

Document Type

Article

Date of this Version

2004

Comments

Published in J. Phys. Chem. A 2004, 108, 10094-10098.

Abstract

Matrix isolation infrared spectroscopy has been combined with theoretical calculations for the characterization of the 1:1 hydrogen-bonded complex between H₂O and dimethyl methylphosphonate (DMMP). The symmetric O-H stretching mode was observed to shift 203 cm^-1 to lower energy upon hydrogen bond formation, while a 32 cm^-1 blue shift was noted for the H-O-H bending mode of the H₂O subunit in the complex. These values compare extremely well with the (unscaled) shifts of -203 and +32 cm^-1, respectively, that were calculated theoretically at the MP2/6-31+G** level. Additional perturbed modes of the DMMP subunit were observed, shifted relative to the parent band position. The greatest perturbation was to the P=O stretching mode near 1270 cm^-1, where a shift of -17 cm^-1 was observed (-21 cm^-1 calculated theoretically). This suggests that the site of hydrogen bonding in the complex is at the P=O group, in agreement with theoretical calculations. The binding energy ΔE° for the 1:1 complex was calculated to be -7.7 kcal/mol.