title: A Comparative Study of [CaEDTA](2-) and [MgEDTA](2-): Structural and Dynamical Insights from Quantum Mechanical Charge Field Molecular Dynamics.
abstract: Structure and dynamics of [MgEDTA](2-) and [CaEDTA](2-) complexes in aqueous solution have been investigated via quantum mechanical/molecular mechanical (QM/MM) simulations. While for the first a 6-fold octahedral complex has been observed, the presence of an additional coordinating water ligand has been observed in the latter case. Because of rapidly exchanging water molecules, this 7-fold coordination complex was found to form pentagonal bipyramidal as well as capped trigonal prismatic configurations along the simulation interchanging on the picosecond time scale. Also in the case of [MgEDTA](2-) a trigonal prismatic configuration has been observed for a very short time period of approximately 1 ps. This work reports for the first time the presence of trigonal prismatic structures observed in the coordination sphere of [MgEDTA](2-) and [CaEDTA](2-) complexes in aqueous solution. In addition to the detailed characterization of structure and dynamics of the systems, the prediction of the associated infrared spectra indicates that the ion-water vibrational mode found at approximately 250 cm(-1) provides a distinctive measure to experimentally detect the presence of the coordinating water molecule via low-frequency IR setups.
authors.affiliation: Theoretical Chemistry Division Institute of General, Inorganic and Theoretical Chemistry University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria.
authors.forename: Andreas O
authors.initials: AO
authors.lastname: Tirler
authors.affiliation: Theoretical Chemistry Division Institute of General, Inorganic and Theoretical Chemistry University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hofer