title: Exploring structure and dynamics of the diaquotriamminezinc(II) complex by QM/MM MD simulation.
abstract: The structural and dynamical properties of the cis-(O-Zn-O angle approximately 90 degrees) and trans-(O-Zn-O angle approximately 180 degrees) isomers of the model diaquotriamminezinc(II) complex in aqueous solution have been evaluated using the hybrid quantum mechanical/molecular mechanical molecular dynamics simulation approach at ab initio Hartree-Fock level. In both complexes, the first hydration shell contains five ligands (two water and three ammonia molecules) arranged in a trigonal bipyramidal geometry. In the metastable cis-isomer two different bond lengths of 2.34 and 2.13 A are observed for the Zn-Oax and Zn-Oeq bonds, respectively. The trans-isomer shows the maximum of the Zn-O distance at 2.26 A. The Zn-N bond distances in both cases are approximately 2.12 A. A geometrical transformation of the cis-isomer into the trans-isomer was observed after 11.5 ps of simulation, and the trans-isomer then remained stable throughout the whole simulation time of 30 ps. A comparative study for both isomers has been performed in terms of radial distribution functions, coordination number distributions, angular distribution functions, tilt and theta angle distributions, ligands' mean residence time, ion-ligand stretching frequencies, and the vibrational and librational motions of water ligands. The results are compared with the data for the previously studied zinc-monoamine and -diamine complexes.
authors.affiliation: HEJ Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan.
authors.forename: M Qaiser
authors.initials: MQ
authors.lastname: Fatmi
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hofer
authors.forename: Bernhard R
authors.initials: BR
authors.lastname: Randolf
authors.forename: Bernd M
authors.initials: BM
authors.lastname: Rode
mesh_terms: D000588:Amines / Q000737:chemistry*; D003198:Computer Simulation; D007477:Ions / Q000737:chemistry; D007536:Isomerism; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D010100:Oxygen; D011789:Quantum Theory; D012996:Solutions; D013057:Spectrum Analysis; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D000588:Amines; D007477:Ions; D008024:Ligands; D012996:Solutions; D017967:Zinc Compounds; D010100:Oxygen