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

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(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 (lambda(max) = 330-405 and 417-458 nm, respectively, epsilon(max) = (3-6) x 10(3) dm(3) mol(-1) cm(-1)) are assigned as d(pi)(Ru-II) - pi*(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 lambda(max) = 477-601 nm. Density functional theory (DFT) calculations and charge decomposition analysis (CDA) have been used to compare the or-donating and pi-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(mu-Cl)(3)Ru(Me(3)Tacn)](+) has also been determined, and the Ru center dot center dot center dot Ru distance has been found to be 3.1842(6) angstrom.