Luminescence and spectroscopic studies of organometallic rhodium and rhenium multichromophore systems carrying polypyridyl acceptor sites and phenylethynyl antenna subunits

Using the Alkynyl-Substituted Rhenium(I) Complex (4,4′-Bisphenyl-Ethynyl-2,2′-Bipyridyl)Re(CO)3Cl as Catalyst for CO2 Reduction—Synthesis, Characterization, and Application

“…Also, these complexes usually display less intense metal-to-ligand charge transfer (MLCT) signatures at lower energies [11,20,21]. In acetonitrile, compound (1) (red line) is characterized by a broad absorption maximum at around 400 nm, red-shifted compared to (3) (black line) with a maximum at about 365 nm.…”

“…It should be noted that the absorption features of the tricarbonylchlororhenium(I) polypyridyl complexes of the (LL)Re(CO) 3 Cl-type are known to be sensitive to the nature of the solvent. It was found that the visible spectra of all rhenium complexes undergo a bathochromic shift with decreasing solvent polarity; therefore, slightly different values for the absorption maxima of (2) and Scheme 2 Synthesis sequence from 2,2′-bipyridine (4) to 4,4′-bis(phenylethynylene)-2,2′-bipyridine (9) (3) have been reported when different solvents were used [10,11,20]. A normalized absorption spectra of compound (1) in dimethylformamide (DMF) solution can be found in the supplementary information Fig.…”

“…The infrared (IR) spectrum of complexes of the (LL)Re(CO) 3 Cl-type are dominated by their characteristic signals connected to the C≡O vibrations positioned at around 1900 and 2000 cm −1 , respectively [9,11]. As the IR absorption bands of the C≡O vibrations are dominant in the spectra and reside in the frequency region where no other absorption bands exist, these bands are useful to probe the electronic exited states of these compounds.…”

“…Studies show that these catalysts yield CO as the main reduction product with almost no hydrogen and formic acid formed as side products [7][8][9][10]. It has been shown that the metal-centered and the metal-to-ligand charge-transfer (MLCT) electronic states can be altered by ligand modification [11,12]. Recently, our group reported the synthesis, structure, photophysics, spectroscopic characterization, and catalytic activity of the modified rhenium complex (5,5′-bisphenylethynyl-2,2′-bipyridyl)Re(CO) 3 Cl, carrying additional phenylethynyl substituents at the acceptor ligand on the 5,5′-position compared to the well-studied (2,2′-bipyridyl)-Re(CO) 3 Cl [11,13].…”

“…It has been shown that the metal-centered and the metal-to-ligand charge-transfer (MLCT) electronic states can be altered by ligand modification [11,12]. Recently, our group reported the synthesis, structure, photophysics, spectroscopic characterization, and catalytic activity of the modified rhenium complex (5,5′-bisphenylethynyl-2,2′-bipyridyl)Re(CO) 3 Cl, carrying additional phenylethynyl substituents at the acceptor ligand on the 5,5′-position compared to the well-studied (2,2′-bipyridyl)-Re(CO) 3 Cl [11,13]. This new compound has an extended conjugated π-electron system that shifts the optical absorption of the intraligand bands into the visible spectral range which is considered an important benefit for potential photocatalytic applications.…”