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, Me 3 Tacn/1,4,7-trithiacyclononane, [9]aneS3) and aromatic diimine (1,10-phenanthroline, phen/2,2′-bipyridine, bpy) have been prepared. The molecular structures of [(Me 3 Tacn)(bpy)Ru( t -BuNC)] 2+, [([9]aneS3)(phen)Ru( t -BuNC)] 2+, and the nitrile-ligated congener [(Me 3 Tacn)(phen)Ru(CH 3 CN)] 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 (λ max = 330−405 and 417−458 nm, respectively, ε max = (3−6) × 10 3 dm 3 mol −1 cm −1 ) are assigned as d π (Ru II ) → 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 λ max = 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 [(Me 3 Tacn)Ru(μ-Cl) 3 Ru(Me 3 Tacn)] + has also been determined, and the Ru···Ru distance has been found to be 3.1842(6) Å.