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Computational Insights into the Isomerism of Hexacoordinate Metal-Sarcophagine Complexes: The Relationship between Structure and Stability
Stockholm University, Faculty of Science, Department of Organic Chemistry.
2015 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 3, 503-511 p.Article in journal (Refereed) Published
Abstract [en]

The hexacoordinate complexes that the macrobicyclic ligands {(NH3)(2)sar)(2+) and {NMe3)(2)sar}(2+) (sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) form with transition metals such as Co-III, Co-II and Cu-II can adopt several isomeric structures. In this article, we have firstly employed DFT methods lo compute the relative stability of their Delta-ob(3), Delta-ob(2)lel, Delta-lel(2)ob and Delta-lel(3) isomers, as well as the activation barriers for their interconversion. In agreement with the experimental data, the results show that, in general, the different isomers of the Co-III and Co-II complexes present similar free energies, whereas the Cu-II complexes show a strong tendency towards the lel(3) form. In addition, the interplay between the structure and stability of these species has been studied by combining shape maps with a distortion/interaction energy analysis. In contrast to the geometries close to the ideal octahedron that all the studied Co complexes present, the le)3 structures of [Cu{(NH3)(2)sar}](4+) and [Cu{(NMe3)(2)sar](4+) are better described. as trigonal prisms. In such structures the ligand adopts a conformation significantly more stable than in the other isomers, and this drives the formation of lel(3)-[Cu{(NH3)(2)sar}](4+) and lel(3)-[Cu{(NNe3)(2)sar}](4+). Overall, the results show a clear relationship between the stability of a given isomer and its degree of distortion with respect to the ideal octahedron (or trigonal prism), with the latter being ultimately dependent on the transition metal and its radius.

Place, publisher, year, edition, pages
2015. no 3, 503-511 p.
Keyword [en]
Density functional calculations, Energy analysis, Macrocycles, Transition metals, Isomers
National Category
Organic Chemistry
URN: urn:nbn:se:su:diva-115446DOI: 10.1002/ejic.201402984ISI: 000349153500017OAI: diva2:798936


Available from: 2015-03-27 Created: 2015-03-24 Last updated: 2015-03-27Bibliographically approved

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