Ruthenium(II) Isocyanide Complexes Supported by Triazacyclononane/Trithiacyclononane and Aromatic Diimine: Structural, Spectroscopic, and Theoretical Studies

Abstract

Ruthenium(II)−isocyanide complexes bearing cyclic tridentate amine/thioether (1,4,7-trimethyl-1,4,7-triazacyclononane, Me3Tacn/1,4,7-trithiacyclononane, [9]aneS3) and aromatic diimine (1,10-phenanthroline, phen/2,2′-bipyridine, bpy) have been prepared. The molecular structures of [(Me3Tacn)(bpy)Ru(t-BuNC)]2+, [([9]aneS3)(phen)Ru(t-BuNC)]2+, and the nitrile-ligated congener [(Me3Tacn)(phen)Ru(CH3CN)]2+ show that the Ru−C distances in the isocyanide complexes are sensitive to the electron richness of the metal center, and isocyanide has a stronger trans influence than nitrile. The lowest-energy dipole-allowed absorptions for the isocyanide and nitrile complexes (λmax = 330−405 and 417−458 nm, respectively, εmax = (3−6) × 103 dm3 mol−1 cm−1) are assigned as dπ(RuII) → π*(diimine) metal-to-ligand charge transfer (MLCT) transitions. These complexes are emissive in glassy MeOH/EtOH at 77 K upon photoexcitation and give emission at λmax = 477−601 nm. Density functional theory (DFT) calculations and charge decomposition analysis (CDA) have been used to compare the σ-donating and π-accepting abilities of nitrile and different organometallic ligands including isocyanide, methoxycarbene, and allenylidene. The molecular structure of the cofacial bioctahedral complex [(Me3Tacn)Ru(μ-Cl)3Ru(Me3Tacn)]+ has also been determined, and the Ru···Ru distance has been found to be 3.1842(6) Å.

Chlorido(4,4′-dimethoxy-2,2′-bipyridine)(1,4,7-trimethyl-1,4,7-triazacyclononane)ruthenium(II) perchlorate acetonitrile disolvate and aqua(4,4′-dimethoxy-2,2′-bipyridine)(1,4,7-trimethyl-1,4,7-triazacyclononane)ruthenium(II) bis(perchlorate) dihydrate

“…The tilting direction is toward the aqua and chloride ligands in these cases and it is most probably due to the steric hindrance caused by the methyl group from the tmtacn ligand. The same behaviour is observed in related complexes (Cheng et al, 1994(Cheng et al, , 1996Wong et al, 2009).…”

A Ruthenium(II) Complex Supported by Trithiacyclononane and Aromatic Diimine Ligand as Luminescent Switch-On Probe for Biomolecule Detection and Protein Staining

“…Excitation of 1 ′ (31 μM) at 450 nm in acetonitrile resulted in an emission with λ max at 692 nm, a quantum yield of 2.334 × 10 −3 , and a lifetime of 0.272 μs. This emission was assigned as the triplet d π (Ru II ) → π*(N ∧ N) charge-transfer in nature based on comparison with analogous complexes reported previously 7 37 38 39 40 41 42 43 44 45 46 47 . The replacement of the bpy ligand with dcmb has been previously reported to red-shift the emission maximum of ruthenium(II) complexes 48 .…”

Photophysical properties of metal complexes

“…The complexes are luminescent at 77 K and show tuning of emission based on the nature of the monodentate ligand X. 121,122 PET has been investigated in Ru and Os terpy-based donor-accept dyads VI using femtosecond pump-probe absorption spectroscopy. Ultra-fast electron transfer rates of up to B2 Â 10 11 s À1 were measured for osmium-based systems which show efficient quenching of 3 MLCT emission.…”