E→Z photoinduced isomerization and hydrogen bonding in the peri-acetamido substituted (1H-pyrrol-2-ylmethylene)benzocycloalkanones

Mark V. Sigalov, Bagrat A. Shainyan, Nina N. Chipanina, Larisa P. Oznobikhina, Anton V. Kuzmin

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4 Scopus citations

Abstract

An unusual effect of hydrogen bond strengthening upon coordination of the basic center with another H-bond donor, recently observed for OH⋯O⋯HN bifurcated system in (2Z)-7-hydroxy-2-(1H-pyrrol-2-ylmethylene)indan-1-one was examined for NH⋯O⋯HN intramolecular bifurcated H-bonds in the first synthesized N-[3-oxo-2-(1H-pyrrol-2-ylmethylene)-2,3-dihydro-1H-inden-4-yl]acetamide and N-[8-oxo-7-(1H-pyrrol-2-ylmethylene)-5,6,7,8-tetrahydronaphthalen-1-yl]acetamide. FT-IR, UV–vis, NMR and theoretical calculations including QTAIM analysis were applied to study the UV-induced reversible E⇆Z isomerization of the synthesized compounds. Depending on the strength and length determined by the structure of the molecule, the intramolecular AcNH∙∙∙O hydrogen bond in the E-isomers is either strengthened or weakened in the Z-isomers. The conclusion is made that weak hydrogen bonds may show unusual mutual reinforcement, whereas strong hydrogen bonds reveal antibate dependence of the lengths and energies of the components.

Original languageEnglish
Article number131202
JournalTetrahedron
Volume76
Issue number21
DOIs
StatePublished - 22 May 2020

Keywords

  • DFT calculations
  • Hydrogen bonding
  • IR and UV spectroscopy
  • NMR
  • Photoinduced isomerization

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