Impact of the Anthryl Linking Mode on the Photophysics and Excited-State Dynamics of Re(I) Complexes [ReCl(CO)(4'-An-terpy-κN)].

Rhenium(I) complexes with 2,2':6',2″-terpyridines (terpy) substituted with 9-anthryl () and 2-anthryl () were synthesized, and the impact of the anthryl linking mode on the ground- and excited-state properties of resulting complexes [ReCl(CO)(4'-An-terpy-κN)] (An─anthryl) was investigated using a combination of steady-state and time-resolved optical techniques accompanied by theoretical calculations. Different attachment positions of anthracene modify the overlap between the molecular orbitals and thus the electronic coupling of the anthracene and {ReCl(CO)(terpy-κN)} chromophores. Following the femtosecond transient absorption, the lowest triplet excited state of both complexes was found to be localized on the anthracene chromophore. The striking difference between and concerns the triplet-state formation dynamics. A more planar geometry of 2-anthryl-terpy (), and thus better electronic communication between the anthracene and {ReCl(CO)(terpy-κN)} chromophores, facilitates the formation of the An triplet state. In steady-state photoluminescence spectra, the population ratio of MLCT and An was found to be dependent not only on the anthryl linking mode but also on solvent polarity and excitation wavelengths. In dimethyl sulfoxide (DMSO), compounds and excited with λ > 410 nm show both MLCT and An emissions, which are rarely observed. Additionally, the abilities of the designed complexes for O generation and light emission under the external voltage were preliminary examined.