Abstract
The conformational behavior of ten diheteroaryl ketones and thioketones is investigated using various quantum chemical methods. These ketones and thioketones are formed by the disubstitution of formaldehyde and thioformaldehyde with such a heteroaryl group as 2-furanyl, 2-thiophenyl, 2-selenophenyl, 2-pyrrolyl or 1-methyl-2-pyrrolyl. For these compounds, their conformational preference and the energetic ordering of their conformers are determined at the MP2 and B3LYP levels of theory. Energetic barriers resulting from the interconversion between conformations are also estimated. The natural bond orbital (NBO) and interacting quantum atoms (IQA) methods are used to study fundamental intramolecular energetic effects influencing the stability of individual conformers. The results of the two methods indicate the great significance of the effect associated with electron delocalization (in the form of either NBO donor–acceptor interactions or the IQA interatomic exchange–correlation interaction energy) in governing the conformational behavior of the investigated diheteroaryl ketones and thioketones.
Highlights
Chemical compounds exhibit many physical, chemical and biological properties that are closely related to the molecular structure of the compounds
The results of the two methods indicate the great significance of the effect associated with electron delocalization in governing the conformational behavior of the investigated diheteroaryl ketones and thioketones
The sequence of its three conformations is ordered with respect to increasing energy and the energy of each conformation in the sequence is calculated relative to the energy of the preferred conformation, that is, the lowest energy one
Summary
Chemical compounds exhibit many physical, chemical and biological properties that are closely related to the molecular structure of the compounds. For compounds 1a–5a and 1b–5b, the occurrence of conformational isomerism in their molecules results from the rotations of the whole heteroaryl substituents about the single bonds between these substituents and the carbon atom of (thio)carbonyl group. We extend the analysis of the conformational behavior of the compounds in question and two quantum chemical methods with great interpretative potential, namely the natural bond order (NBO) analysis and the interacting quantum atoms (IQA) method, are employed to explain the conformational behavior from different perspectives It is of great interest for us to establish whether these methods yield a consistent view of the conformational behavior of 1a–5a and 1b–5b. NBO archive files (*.47) and AIM extended wave function files (*.wfx) required by the above-mentioned programs have been generated by GAUSSIAN 09 D.01 [37]
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