Quantum chemical modeling of 2,2´-bipyridine-6,6´-dicarboxylic acid diamide structures: a relationship between the extraction ability and conformational behavior of the ligands

Autor: Nataliya E. Borisova, Marina D. Reshetova
Rok vydání: 2015
Předmět:
Zdroj: Russian Chemical Bulletin. 64:1882-1890
ISSN: 1573-9171
1066-5285
DOI: 10.1007/s11172-015-1088-y
Popis: Approaches to the theoretical evaluation of a comparative affinity to metal ions of 2,2´-bipyridine-6,6´-dicarboxylic acid diamides, which are new promising extracting agents for the isolation of minor actinides from highly acidic radioactive waste, were tested in terms of the density functional theory (DFT) with the PBE0 functional in the TZ basis sets. The amides containing an aromatic substituent are more preorganized for binding with metal ion than their tetraalkyl-substituted analogs. However, the influence of substituents in the aromatic fragment of the molecule is very weak. The introduction of substituents into the pyridine or anilide fragment of the diamide molecule exerts almost no effect on the conformational dynamics and on the charges on the heteroatoms, whereas the extraction behavior depends strongly on these factors. The estimation of the affinity to metal ions by the calculation of the reorganization energy of the ligand for binding in a complex with metal gave the results differed from those calculated by the PBE0 method. The obtained values of the energies correlate well with the distribution coefficients of lanthanides for extraction from nitric acid solutions (Pearson´s coefficient is–0.86 for 0.5 M HNO3 and–0.91 for 1 M HNO3) and also are well described in the framework of the linear model. The method for the estimation of reorganization energies is more timeand labor-consuming than an analysis of the conformational behavior but gives much better results because makes it possible to evaluate qualitatively preorganization and find quantitative parameters for this estimation.
Databáze: OpenAIRE
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