Impact of the Anthryl Linking Mode on the Photophysics and Excited-State Dynamics of Re(I) Complexes [ReCl(CO)₃(4′-An-terpy-κ²N)]

Abstract

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.

Pyrenyl-Substituted Imidazo[4,5-f][1,10]phenanthroline Rhenium(I) Complexes with Record-High Triplet Excited-State Lifetimes at Room Temperature: Steric Control of Photoinduced Processes in Bichromophoric Systems

“…While complex 2 presents only a vibronically structured emission band attributed to the 3 π pyrene , the frozen-state emission spectrum of 1 includes both ligand-based fluorescence ( 1 IL) and phosphorescence ( 3 π pyrene ) components. The bathochromic shift of the phosphorescence for complex 1 in comparison to 2 indicates significantly larger participation of 3 ILCT ( 3 π pyrene → 3 π*­(imphen)) in the case of 1 . The triplet excited-state lifetimes of pyrenyl-substituted Re­(I) complexes (∼170 ms for 1 and ∼370 ms 2 ) are shorter than that for free pyrene (700 ms) , but a few orders of magnitude longer than those for parent chromophores at 77 K (average on 7.76 μs for 3 and 11.85 μs for 4 ).…”

“…Emission spectra as well as the time-resolved measurements of argon-saturated samples in DMSO solutions or ethanol:methanol 77 K frozen matrix (4:1 v/v) were measured on a FLS-980 fluorescence spectrophotometer (Edinburgh Instruments). The fs-TA spectra were measured using a pump–probe transient absorption spectroscopy system (Ultrafast Systems, Helios) described previously. , Singlet oxygen generation ( 1 O 2 ) efficiency was determined using the Evolution 220 UV–vis spectrometer in DMSO with 1,3-diphenylisobenzofuran (DPBF) as a sensitizer. Triplet–triplet annihilation upconversion experiments were performed on the FLS-980 fluorescence spectrophotometer with 9,10-diphenylanthracene (DPA) as a triplet acceptor.…”

“…The bathochromic shift of the phosphorescence for complex 1 in comparison to 2 indicates significantly larger participation of 3 ILCT ( 3 π pyrene → 3 π*(imphen)) in the case of 1. 70 The triplet excited-state lifetimes of pyrenyl-substituted Re(I) complexes (∼170 ms for 1 and ∼370 ms 2) are shorter than that for free pyrene (700 ms) 71,72 but a few orders of magnitude longer than those for parent chromophores at 77 K (average on 7.76 μs for 3 and 11.85 μs for 4). To estimate the energy gap between the 3 MLCT and 3 IL pyrene triplet excited states in the pyrene-substituted Re(I) carbonyls (1 and 2), two different methodologies were used.…”

“…frozen matrix (4:1 v/v) were measured on a FLS-980 fluorescence spectrophotometer (Edinburgh Instruments). The fs-TA spectra were measured using a pump−probe transient absorption spectroscopy system (Ultrafast Systems, Helios) described previously 37,70. Singlet oxygen generation ( 1 O 2 ) efficiency was determined using the Evolution 220 UV−vis spectrometer in DMSO with 1,3diphenylisobenzofuran (DPBF) as a sensitizer.…”

Electrocatalytic reduction of CO2 to CO by a series of organometallic Re(i)-tpy complexes

“…Re(tpy)(CO) 3 X compounds show photochemical properties such as UV emitter, fluorescence, and NIRemitter. [54][55][56][57][58] Herein, we report the synthesis and electrocatalytic properties of a series of fac-Re(I)(L)(CO) 3 Br complexes containing 4′-substituted-2,2′:6′,2″-terpyridine ligands (L). Five Re-complexes (Re1-5) containing 4′-substituents with varying elec-tronic properties were synthesised, and their structures are shown in Fig.…”