Structural, electronic and computational studies of heteroleptic Cu(I) complexes of 6,6′-dimesityl-2,2′-bipyridine with sulfur-substituted dipyridophenazine ligands

A series of stable heteroleptic Cu(I) complexes of 6,6′-dimesityl-2,2′-bipyridine with three sulfur-substituted dipyridophenazine ligands, and unsubstituted dppz are synthesized and studied. The X-ray crystal structures of the complexes display coordinative flexibility of the Cu(I) metal ion and display strong intramolecular π–π stacking interactions. The coordination geometries of the Cu(I) metal centers are characterized by the τ4 parameter, and range from 0.626 for [Cu(bpy(Mes)2)(dppz(Sdec)2]BF4 to 0.757 for [Cu(bpy(Mes)2)(dppzS2CS)]BF4. Cyclic voltammetry reveals Cu(I)/Cu(II) oxidation potentials around 0.83 V for all the complexes studied, consistent with a similar coordination environment of the complexes in solution. The ligand-based reduction potentials are consistent with the electronic nature of the sulfur substituent. Resonance Raman spectroscopy and TD-DFT calculations reveal the presence of an MLCT → bipyridine transition with 488 and 514.5 nm excitation, and dppz-type chromophores ranging from UV (351 nm) to the visible (457 nm) excitation wavelengths. For [Cu(bpy(Mes)2)(dppzS2CS)]BF4 and [Cu(bpy(Mes)2)(dppz(Sdec)2]BF4 the most intense optical transition at 434 and 442 nm respectively are assigned as intraligand (IL)/MLCT transitions.

Four heterolepticCu(I) complexes of 6,6′-dimesityl-2,2′-bipyridine with substituted dipyridophenazine ligands have been synthesized. The complexes are characterized by X-ray crystallography and cyclic voltammetry. The optical properties are investigated by TD-DFT calculations and resonance Raman spectroscopy.Figure optionsDownload as PowerPoint slideHighlights
► Four heteroleptic Cu(I) complexes of 6,6′-dimesityl-2,2′-bipyridine with substituted dipyridophenazine ligands have been synthesized.
► The complexes are characterized by X-ray crystallography.
► Optical properties are investigated by resonance Raman spectroscopy and TD-DFT calculations.