An investigation of the frontier orbital electron density of the antibacterial agent urotropine by electron momentum spectroscopy

The outermost valence (HOMO) orbital electron density distribution for the antibacterial agent urotropine has been studied by electron momentum spectroscopy. The experimental results are compared with quantum chemical calculations within the plane-wave impulse approximation and the target Hartree-Fock or target Kohn-Sham approximations. For the HOMO of urotropine density functional theory calculations with the B3PW91 and B3LYP functionals and 6-311++G{*}{*} and AUG-CC-PVTZ basis sets provide quite good quantitative agreement with the experimental results, while Hartree-Fock calculations fail to adequately describe the experimental momentum distributions. This indicates the importance of taking into account electron correlation for accurate predictions of the frontier (HOMO) orbital electron density and thus the reactive properties of this molecule. (C) 2001 Elsevier Science B.V. All rights reserved.