Synthesis, spectroscopic, electrochemical and computational studies of rhenium(i) dicarbonyl complexes based on meridionally-coordinated 2,2′:6′,2′′-terpyridine

Abstract

A homologous series of meridionally-coordinated tridentate 2,2':6',2''-terpyridine Re(I) dicarbonyl complexes have been prepared and investigated. The complexes mer,cis-[Re(tpy-κ(3)N)(CO)2(L)](n) (L = Cl(-) (1), OSO2CF3(-) (2), NCCH3 (3), CN(-) (4), NC5H5 (5), PMe3 (6), PEt3 (7), PPh3 (8), P(OMe)3 (9) and P(OEt)3 (10); n = 0 or +1) have been synthesized and characterized by elemental analysis, (1)H NMR and infrared spectroscopy. The electrochemistry of these compounds has been studied and compared to that of other known rhenium compounds using an electrochemical parameterization model. Cyclic voltammetry measurements have shown that the first oxidation of the complexes varies systematically in potential as the ligand L is altered. Many of these one-electron oxidations occur at lower potentials compared to more familiar bidentate diimine Re(I) tricarbonyl complexes. A correlation exists between CO, a strong π-acidic ligand, and deviations of the observed reduction potentials from the calculated values. Many of the complexes absorb light throughout a significant portion of the visible spectrum. Two of these complexes, mer,cis-Re(tpy-κ(3)N)(CO)2Cl (1) and mer,cis-Re(tpy-κ(3)N)(CO)2CN (4), absorb light throughout the entire visible spectrum. Low temperature emission spectra were obtained for the compounds mer,cis-Re(tpy-κ(3)N)(CO)2Cl (1) and mer,cis-[Re(tpy-κ(3)N)(CO)2(P(OEt)3)](+) (10) at 77 K in a 4 : 1 methanol-ethanol glass matrix and give metal-to-ligand charge transfer ((3)MLCT) luminescence. Density functional theory (DFT) calculations of the electronic structure are in good agreement with the experimental data.

Visible and Near‐IR Emissions from k2N‐ and k3N‐Terpyridine Rhenium(I) Assemblies Obtained by an [n×1] Head‐to‐Tail Bonding Strategy

“…The results for the k 2 N ‐species are in good agreement with those reported for other k 2 N ‐terpyridine fac ‐rhenium tricarbonyl species . The experimental infrared spectrum of the k 3 N ‐species features two strong stretching vibrations in the region ν ≈1800–1900 cm −1 , consistent with both the theoretical data and observations for previously studied rhenium dicarbonyl species …”

“…As shown in Table , the calculated adiabatic electronic emission ( λ AE ), corresponding to the energy gap between the optimized T 1 geometry and the ground state S 0 , slightly overestimates the luminescence wavelength by about 50–70 nm. As reported previously, the k 3 N ‐species were found to be non‐emissive at room temperature up to 800 nm ,,. Therefore, we conducted luminescence studies on the k 3 N ‐species in the infrared region (Figure , Figure S16, and Table S25).…”

“…The ligand 4‐pytpy and metal complexes 1 – 4 were prepared according to previously published literature procedures (Scheme ) ,. The species were isolated in average to good yields and were purified by recrystallization.…”

Coordination Environment Prevents Access to Intraligand Charge-Transfer States through Remote Substitution in Rhenium(I) Terpyridinedicarbonyl Complexes

“…The κ 3 N -dicarbonyl complexes studied in this work (3a-f ) were obtained as air-stable black solids in quantitative yields by thermal decarbonylation of 2a-f under vacuum (Scheme 1), an improved protocol respect to previous literature reports. [37][38][39] The key aspect to quantitative conversion is heating the complexes under vacuum (instead of under inert atmosphere), as this is expected to promote CO loss. Complete experimental details are provided in the Supporting Information (SI).…”

A Novel 2,6-Bis(8’-quinolinyl)pyridine Rhenium Compound

“…Previously, we prepared a homologous series of meridionallycoordinated tridentate terpyridine Re(I) complexes containing two carbon monoxide co-ligands. [9,10] The complexes all absorb light throughout a significant portion of the visible spectrum, and several of them absorb light throughout the entire visible progressed. The solution was allowed to cool and evaporated to dryness under reduced pressure.…”