Substituted Pyrrole‐based Schiff Bases: Effect On The Luminescence Of Neutral Heteroleptic Cu(I) Complexes

Neutral Cu(I) complexes containing Schiff bases as chelating N-donors and phosphines as P-donors were efficiently isolated and characterized. The imines were obtained by straightforward condensation between pyrrole-2-carboxaldehyde and the corresponding aromatic amines. The structure of most of the Cu(I) species was elucidated through single-crystal X-ray diffraction. The Cu(I) complexes exhibited intense absorptions around 400–500 nm ascribed to MLCT transitions. For some Cu(I) derivatives, orange- and red-orange emissions were detected upon excitation with near-UV and blue irradiation in the solid state. The emission maxima were red-shifted once the benzothiazole-derived Schiff base or Xantphos were employed as chelating ligands. Microsecond-long lifetimes, wide emissions, and large Stokes shifts suggest the involvement of triplet states in the luminescent process. Electrochemical measurements and DFT calculations were employed to rationalize the photoluminescence properties, which were ascribed to mixed $^3$LC/$^3$MLCT transitions.