Importance of water and intramolecular interaction governs substantial blue shift of Csp2-H stretching frequency in complexes between chalcogenoaldehydes and water

Geometrical structure, stability and cooperativity, and contribution of hydrogen bonds to the stability of complexes between chalcogenoaldehydes and water were thoroughly investigated using quantum chemical methods. The stability of the complexes increases significantly when one or more H2O molecules are added to the binary system, whereas it decreases sharply going from O to S, Se, or Te substitution. The O-HMIDLINE HORIZONTAL ELLIPSISO H-bond is twice as stable as C-sp(2)-HMIDLINE HORIZONTAL ELLIPSISO and O-HMIDLINE HORIZONTAL ELLIPSISS/Se/Te H-bonds. It is found that a considerable blue-shift of C-sp(2)-H stretching frequency in the C-sp(2)-HMIDLINE HORIZONTAL ELLIPSISO H-bond is mainly determined by an addition of water into the complexes along with the low polarity of the C-sp(2)-H covalent bond in formaldehyde and acetaldehyde. The C-sp(2)-H stretching frequency shift as a function of net second hyperconjugative energy for the sigma*(C-sp(2)-H) antibonding orbital is observed. Remarkably, a considerable C-sp(2)-H blue shift of 109 cm(-1) has been reported for the first time. Upon the addition of H2O into the binary systems, halogenated complexes witness a decreasing magnitude of the C-sp(2)-H stretching frequency blue-shift in the C-sp(2)-HMIDLINE HORIZONTAL ELLIPSISO H-bond, whereas CH3-substituted complexes experience the opposite trend.

Automated summary

This study thoroughly investigated the geometrical structure, stability, and cooperativity of complexes between chalcogenoaldehydes and water using quantum chemical methods. The addition of H2O molecules significantly increased the stability of the complexes, while substitution with S, Se, or Te led to a sharp decrease in stability. The study also reported a considerable blue-shift of the C-sp(2)-H stretching frequency in the C-sp(2)-HMIDLINE HORIZONTAL ELLIPSISO H-bond, and observed a significant C-sp(2)-H blue shift of 109 cm(-1) for the first time.