Faculty of Sciences
Department of Chemistry and Industry
BP 190 KINSHASA XI
PHYSICAL AND STRUCTURAL CHEMISTRY LABORATORY

LUNDEMBA SINGA Albert

Graduate of Advanced Studies in Chemical Sciences

Dissertation

Presented and defended with a view to obtaining the Degree of Doctor of Science
Group: Chemistry

Promoter: Dr. YAV GUSHIMANA ZEPHYRIN
Ordinary Professor

SUMMARY

The growing interest in noncovalent interactions involving chalcogen atoms, such as hydrogen bonds, aromatic contacts, n-hole and o-bole bonds, has been attributed to their importance in crystal engineering, molecular structure recognition, and macromolecular structures. The present study deals with chalcogen bonds involving divalent sulfur, selenium, and tellurium atoms, acting as sigma hole donors, in small molecules using the Cambridge Structural Database (CSD) in conjunction with ab initio calculations. The results derived from the CSD search and computational study revealed that the nucleophiles formed complexes with the chalcogen bond donors Ri-Ch-R2 (Ch = S, Se, or Te). The main forces stabilizing the complexes were the chalcogen bonds, enhanced by dispersion interactions. The complexes and calculated energies show that the bond with the nucleophile at the divalent atoms S, Se and Te is a directed and relatively strong interaction. The strength of the interaction depends on the nature of the substituents Ri and R2. According to CSD analysis and ab initio calculations, the ability of the chalcogen to form the interaction increases along the sequence S < Se < Te in the same environment. The bond consists of a charge transfer from a lone pair of electrons of nucleophile atoms to an antibonding orbital Ch-Ri or Ch-R2.
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