Photoswitchable N-Heterocyclic Carbenes: Using Light to Modulate Electron-Donating Properties


  • We are grateful to the ARO (W911NF-09-1-0446), the NSF (CHE-0645563), and the Welch Foundation (F-1621) for their generous support.


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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.