| This research used molecular modeling to predict the geometry and the properties of atrazine. The initial investigation is a semi-empirical (PM3) study of atrazine dimer hydration in which the supermolecule approach is used to simulate a solvent sheath of water molecules varying from 7 to 24 H 2O's around an atrazine dimer. In the case of the atrazine dimer hydrated with 21 water molecules, the removal of one water molecule results in rearrangement of the majority of the solvent sheath. This is accompanied by a change in the number of hydrogen bonds and the average hydrogen bond distance between water molecules, ring chlorines, a ring nitrogen and other water molecules. A semi-empirical (PM3) study of atrazine dimer formation and atrazine monomer and dimer complexes containing Mg2+, Ca2+, Cd 2+, Pb2+, or Zn2+ is also reported. The atrazine molecules in metal ion-atrazine dimer complexes provide ring and sidechain nitrogens that bind to Mg2+, Ca2+, Cd2+, Pb2+, or Zn2+. The majority of metal ion sidechain nitrogen interactions involve the -N-i-propyl rather than the -N-ethyl sidechain nitrogen. The results from the direct implementation of gauge-including atomic orbital (GIAO) methods for calculating nuclear magnetic shielding tensors at both the Hartree-Fock and density functional level of theory (DFT) are presented. Isotropic 1H and 13C magnetic shielding constants for atrazine and atrazine dimers are reported and compared with experimental results. |
