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Title
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Homonuclear chalcogen–chalcogen bond interactions in complexes pairing YO3 and YHX molecules (Y = S, Se; X = H, Cl, Br, CCH, NC, OH, OCH3): Influence of substitution and cooperativity
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Abstract
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MP2/aug-cc-pVTZ calculations are performed on complexes of YO3 (Y=S, Se) with a series of electron-donating chalcogen bases YHX (X=H, Cl, Br, CCH, NC, OH, OCH3). These complexes are formed through the interaction of a positive electrostatic potential region (π-hole) on the YO3 molecule with the negative region in YHX. Interaction energies of the binary O3Y•••YHX complexes are in the range of -4.37 to -12.09 kcal/mol. The quantum theory of atoms in molecules and the natural bond orbital analysis were applied to characterize the nature of interactions. It was found that the formation and stability of these binary complexes are ruled mainly by electrostatic effects, although the electron charge transfer from YHX to YO3 unit seems to play also an important role. In addition, mutual influence between the Y•••N and Y•••Y interactions are studied in the ternary HCN···O3Y···YHX complexes. The results indicate that the formation of a Y•••N interaction tends to weaken Y•••Y bond in the ternary systems. Although the Y•••Y interaction is weaker than the Y•••N one, however, both types of interactions seem to compete with each other in the HCN···O3Y···YHX complexes.
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