Neutral, Heteroleptic [Cu(I)(PPh3)2(4H‐imidazolato)] Complexes: Ligand Exchange Reactivity, Redox Properties, Excited‐State Dynamics
Hop on hop off: Typically, heteroleptic Cu(I)DiiminePPh3 complexes tend to form the homoleptic counterpart. But this is not observed when the diimine is an anionic 4H-imidazolate. Despite dynamic PPh3 ligand exchange in solution the deeply colored, photoredox-active Cu(I)4H-imidazolatoPPh3 complexes are stable.
Cu(I) 4H-imidazolate complexes are rare examples of Cu(I) complexes with chelating anionic ligands and are potent photosensitizers with unique absorption and photoredox properties. In this contribution, five novel heteroleptic Cu(I) complexes with monodentate triphenylphosphine co-ligands are investigated. As a consequence of the anionic 4H-imidazolate ligand and in contrast to comparable complexes with neutral ligands, these complexes are more stable than their homoleptic bis(4H-imidazolato)Cu(I) congeners. Here, the ligand exchange reactivity was studied by 31P-,19F-, and variable temperature NMR and the ground state structural and electronic properties by X-ray diffraction, absorption spectroscopy, and cyclic voltammetry. The excited-state dynamics were investigated by femto- and nanosecond transient absorption spectroscopy. The observed differences, with respect to chelating bisphosphine bearing congeners, are often due to the increased geometric flexibility of the triphenylphosphines. These observations render the investigated complexes interesting candidates for photo(redox)reactions not accessible with chelating bisphosphine ligands.Zum Volltext
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