Structural, Electronic, and Computational Studies of Heteroleptic Cu(I) Complexes of 6,6′-Dimesityl-2,2′-bipyridine with Ferrocene-Appended Ethynyl-2,2′-bipyridine Ligands

Optical characterization and computational modeling of three ferrocene-appended ethynyl-2,2'-bipyridine ligands and the associated heteroleptic copper(I) complexes of 6,6'-dimesityl-2,2'-bipyridine are reported. These dyes have been studied using electrochemical analysis, electronic absorption, and Raman and resonance Raman spectroscopies, coupled with density functional theoretical approaches. For the complexes, optical spectra are dominated by a low energy copper(I) centered metal to ligand charge transfer (MLCT) transition; this is modulated by the presence of pendant ferrocene units and the extent of conjugation of the ferrocenyl bipyridine backbone. Electronic tuning due to ferrocene is shown to result in a redshift of the MCLT transition of up to similar to 0.2 eV, while an elongation of conjugation appears to result in an increased MLCT intensity of around 50%.