A density functional theory- and atoms in molecules-based study of NiNTA and NiNTPA complexes toward physical properties controlling their stability. A new method of computing a formation constant

dc.contributor.authorCukrowski, Ignacy
dc.contributor.authorGovender, Krishna Kuben
dc.contributor.emailignacy.cukrowski@up.ac.zaen_US
dc.date.accessioned2011-02-22T09:37:02Z
dc.date.available2011-02-22T09:37:02Z
dc.date.issued2010-08
dc.description.abstractThe log K1 value of analytical quality was obtained for the NiNTPA complex using the density functional theory (DFT)-computed (at the B3LYP/6-311þþG(d,p) level of theory in solvent, CPCM/UAKS) G(aq) values of the lowest-energy conformers of the ligands, nitrilotriacetic acid (NTA) and nitrilotri-3-propanoic acid (NTPA), and the Ni(II) complexes (NiNTA and NiNTPA). The described mathematical protocol is of a general nature. The topological analysis, based on the quantum theory of atoms in molecules (QTAIM) of Bader, was used to characterize coordination bonds, chelating rings, and additional intramolecular interactions in the complexes. The topological data, but not the structural analysis, explained the observed difference in stability of the NiNTA and NiNTPA complexes. It was found that the structural H 3 3 3 H contacts (classically regarded H-clashes, a steric hindrance destabilizing the complex) are in fact the H-H bonds contributing to the overall stability of NiNTPA. Also a CH-O bond was found in NiNTPA. The absence of intramolecular bonds between the atoms that fulfill a distance criterion in NiNTPA is explained by the formation of adjacent intramolecular rings that have larger electron density at the ring critical points when compared with the rings containing these atoms. It is postulated that the strength of a chelating ring (a chelating effect) can be measured by the electron density at the ring critical point. It was found that the strain energy, Es, in the as-in-complex NTPA ligand (Es is significantly lowered by the presence of the intramolecular bonded interactions found by QTAIM) is responsible for the decrease in strength of NiNTPA; the Es ratio (NTPA/NTA) of 1.9 correlates well with the experimental log K1 ratio (NTA/NTPA) of 1.98.en
dc.description.sponsorshipFinancial support of the National Research Foundation of South Africa and the University of Pretoria.en_US
dc.identifier.citationCukrowski, I & Govender, KK 2010, 'A density functional theory- and atoms in molecules-based study of NiNTA and NiNTPA complexes toward physical properties controlling their stability. A new method of computing a formation constant', Inorganic Chemistry, vol. 49, no. 15, pp. 6931-6941. [http://pubs.acs.org/journal/inocaj]en
dc.identifier.issn0020-1669
dc.identifier.issn1520-510X (online)
dc.identifier.other10.1021/ic100453v
dc.identifier.urihttp://hdl.handle.net/2263/15915
dc.language.isoenen_US
dc.publisherAmerican Chemical Societyen_US
dc.rights© 2010 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/journal/inocaj.en_US
dc.subjectDFT calculationen
dc.subjectQTAIM critical point analysisen
dc.subjectFormation constanten
dc.subjectChelating effecten
dc.subjectStrain energyen
dc.subjectH–H bondingen
dc.subjectCH–O bonden
dc.subjectDensity functional theory (DFT)
dc.subjectNitrilotriacetic acid (NTA)
dc.subjectNitrilotri-3-propanoic acid (NTPA)
dc.subject.lcshDensity functionalsen
dc.subject.lcshFunctional analysisen
dc.subject.lcshNickel (Ni)en
dc.subject.lcshCarboxylic acidsen
dc.titleA density functional theory- and atoms in molecules-based study of NiNTA and NiNTPA complexes toward physical properties controlling their stability. A new method of computing a formation constanten
dc.typePostprint Articleen

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