Impact of the Anthryl Linking Mode on the Photophysics and Excited-State Dynamics of Re(I) Complexes [ReCl(CO) 3 (4'-An-terpy-κ 2 N)].

Rhenium(I) complexes with 2,2':6',2″-terpyridines (terpy) substituted with 9-anthryl ( 1 ) and 2-anthryl ( 2 ) were synthesized, and the impact of the anthryl linking mode on the ground- and excited-state properties of resulting complexes [ReCl(CO) 3 (4'-An-terpy-κ 2 N)] (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) 3 (terpy-κ 2 N)} 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 1 and 2 concerns the triplet-state formation dynamics. A more planar geometry of 2-anthryl-terpy ( 2 ), and thus better electronic communication between the anthracene and {ReCl(CO) 3 (terpy-κ 2 N)} chromophores, facilitates the formation of the 3 An triplet state. In steady-state photoluminescence spectra, the population ratio of 3 MLCT and 3 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 1 and 2 excited with λ exc > 410 nm show both 3 MLCT and 3 An emissions, which are rarely observed. Additionally, the abilities of the designed complexes for 1 O 2 generation and light emission under the external voltage were preliminary examined.