Characteristics and dynamics of excited states populated after excitation at the Soret-like band of dibenzo[g,p]chrysene-fused bis-dicarbacorrole Cu(iii) and Pd(ii) metal complexes

Abstract

Dibenzo[g,p]chrysene-fused bis-dicarbacorrole (Bis-H₃) metal complexes exhibit unique electron configurations and properties that depend on the number and type of coordinated metal centers as there are two coordinative adj-CCNN subunits. When Cu(III) ions are coordinated, the π electrons in the Bis-H₃ ligand are maintained. When Pd(II) ions are coordinated, each Pd(II) would induce one π electron from the Bis-H₃ ligand to be donated to the Pd center; hence, the electron configuration and aromaticity of the Bis-H₃ ligand could be modified by introducing Pd(II) centers. In this research, by applying transient absorption spectroscopy, with a probe range in both the visible and near-infrared ranges, density functional theory and time-dependent density functional theory calculations, it was found that for Bis-H₃ complexes with only Cu(III) centers, the ligand-to-metal charge transfer state could be populated after excitation at its Soret-like band. However, for complexes that include a Pd(II) metal centre, the metal-to-ligand charge transfer state is populated, and its lifetime is much longer than that of Cu(III) only for the Bis-H₃ complex. The charge recombination rate of the Pd(II)-containing Bis-H₃ complex is also found to correspond strongly with the electron–hole distance of the excited state population. For Bis-H₃ metal complexes, the photoinduced electron transfer direction and the corresponding charge recombination rate could be modified by changing the coordinated metal centers.