title: The conformation effect of the diamine bridge on the stability of dinuclear platinum(II) complexes and their hydrolysis.
abstract: In this paper, the hydrolysis process of a bisplatinum complex containing the flexible chain 1,6-hexanediamine between the two metal centers was investigated through the use of density functional theory (DFT) with the analysis of the role of the spacing group arrangement on the values of free energy activation barrier. All structures were fully optimized in aqueous solution using implicit model for solvent at DFT level. The energy profiles for the hydrolysis reaction were determined by using the supermolecule approach. Five transition states were proposed differing by the conformation of the bridge group, and the activation free energy calculated as a weighted average within the selected forms. The Gibbs population for reactant was used as a statistical weight leading to the predicted value of 23.1kcalmol(-1), in good accordance with experiment, 23.8kcalmol(-1). Our results suggests that for 1,6-hexanediamine bridge ligand, the extend forms with average torsional angle over the carbon chain larger than 130° have the greatest contribution to the hydrolysis kinetics. The results presented here point out that the hydrolysis mechanism might follow different paths for each conformation and each of these contributes to the observed energy barrier.
authors: NEQC (Núcleo de Estudos em Química Computacional), Departamento de Química, ICE, Universidade Federal de Juiz de Fora, Campus Universitário Martelos, 36036-900 Juiz de Fora, MG, Brazil.
authors: Lucas F
authors: LF
authors: Esteves
authors: NEQC (Núcleo de Estudos em Química Computacional), Departamento de Química, ICE, Universidade Federal de Juiz de Fora, Campus Universitário Martelos, 36036-900 Juiz de Fora, MG, Brazil.
authors: Hélio F
authors: HF
authors: Dos Santos
authors: NEQC (Núcleo de Estudos em Química Computacional), Departamento de Química, ICE, Universidade Federal de Juiz de Fora, Campus Universitário Martelos, 36036-900 Juiz de Fora, MG, Brazil. Electronic address: luiz.costa@ufjf.edu.br.
authors: Luiz Antônio S
authors: LA
authors: Costa
mesh_terms: D002413:Cations, Divalent; D056831:Coordination Complexes / Q000737:chemistry*; D003959:Diamines / Q000737:chemistry*; D004355:Drug Stability; D006868:Hydrolysis; D007700:Kinetics; D008024:Ligands; D008968:Molecular Conformation; D009944:Organoplatinum Compounds / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D056831:Coordination Complexes; D003959:Diamines; D008024:Ligands; D009944:Organoplatinum Compounds; D014867:Water; D010984:Platinum; C007297:1,6-diaminohexane
keywords: Conformation effects; Hydrolysis; Platinum complexes; Rate constants