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Keywords:

  • carbenes;
  • cyclization;
  • nitrogen heterocycles;
  • photochromism;
  • photoswitch
Thumbnail image of graphical abstract

Ligands in the limelight: Light was used to change the electron-donating properties of an N-heterocyclic carbene (NHC) moiety within chalcogen and metal adducts. Photoinduced electrocyclic ring closure of a photochromic 4,5-dithienylimidazolone increased its νCO frequency. Likewise, UV irradiation of an analogous photochromic [(NHC)Ir(CO)2Cl] complex decreased the carbene's electron-donating ability. Subsequent exposure to visible light reversed both photocyclization reactions.