Dielectric behavior and molecular structure of inorganic complexes

Sorriso, Salvatore

doi:10.1021/cr60326a003

Cited by 6 publications

(1 citation statement)

References 25 publications

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“…The electric dipole moment method can provide an effective means for establishing the geometric structure of metal chelate compounds for investigating the spatial conformation of metal complexes, and also for detecting complexation stability with metal ions. , For these charged metal complexes, the absolute value of the dipole moment depends on the origin of the spatial reference system and the dipole moments are obtained by placing the metal ion at the origin of the coordinates. To describe how the dipole moment changes when going from hydrated to chelated metal complex, we define the dipole moment change as Δμ = μ [M(EDTA)] 2− or [M( S , S -EDDS)] 2− − μ [M(H 2 O) 6 ] 2− , where the values of μ [M(H 2 O) 6 ] 2− are almost zero because of the high symmetries of the hydrated metal complexes.…”

Section: Resultsmentioning

confidence: 99%

Metal Complexation and Biodegradation of EDTA and S,S-EDDS: A Density Functional Theory Study

Chen

Liu

2009

J. Phys. Chem. A

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The complexation reactions of ethylenediaminetetraacetate (EDTA(4-)) and S,S-ethylenediaminedisuccinate (S,S-EDDS(4-)) with Co(2+), Ni(2+), Cu(2+), Zn(2+), and Cd(2+) cations are investigated by using the DFT/B3LYP method. The hydration reaction of each metal ion with solvent water cluster is considered with a mixed cluster/continuum model. The subsequent metal complexation is treated as a substitution reaction of the coordinated water molecules by the amino polycarboxylic acid ligand. Thermodynamic cycles are schemed to evaluate the free energy changes for both hydration and complexation processes. The values of complexation free energy changes show that the stabilities of metal complexes with the isomeric ligands follow the order of [M(S,S-EDDS)](2-) in trans(O(6))-conformer < [M(S,S-EDDS)](2-) in trans(O(5))-conformer < [M(EDTA)](2-), implying that the failure to observe the trans(O(6)) conformer under experimental conditions is attributed to its inherent instability. The same trend appears in our steric strain analysis on the various chelate rings in complexes. Because the [M(S,S-EDDS)](2-) in trans(O(6)) complex is not available, we focus on the other two series of complexes with concerned metal ions. The stabilities decrease in the order Cu(2+) > Ni(2+) > Co(2+) > Zn(2+) > Cd(2+) and Cu(2+) > Ni(2+) > Co(2+) > Cd(2+) > Zn(2+) for trans(O(5))-[M(S,S-EDDS)](2-) and [M(EDTA)](2-), respectively. These two tendencies are shown to be consistent with the decrease in the metal-to-ligand charge transfer. Meanwhile, a good quantitative correlation is found between the complexation free energies and the dipole moments for all complexes (excluding the case of Cu(2+)). The far-infrared spectra are present to investigate the characteristics of metal-dependent vibrations, and the further natural bond orbital (NBO) method is taken to show the nature of metal-ligand bonding interactions. Finally, and perhaps most importantly, degrading products of both amino polycarboxylic acids are successfully predicted through calculating the dissociation energies of all C-N bonds in free EDTA, S,S-EDDS, and their successive products. Degradation mechanisms with intramolecular hydrogen transfer are proposed for the biodegradation reactions of S,S-EDDS and its product N-(2-aminoethyl) aspartic acid (AEAA).

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Section: Resultsmentioning

confidence: 99%