trans-Diaqua­bis(2,2′-bipyridine-κ2 N,N′)ruthenium(II) bis­(trifluoro­methane­sulfonate)

The title compound, trans-[Ru(bpy)2(H2O)2](CF3SO3)2 (bpy = 2,2′-bipyridine, C10H8N2), crystallized from the decomposition of an aged aqueous solution of a dimeric complex of cis-Ru(bpy)2 in 0.1 M triflic acid. The RuII ion is located on a crystallographic inversion center and exhibits a distorted octa­hedral coordination with equivalent ligands trans to each other. The Ru—O distance is 2.1053 (16) Å and the Ru—N distances are 2.0727 (17) and 2.0739 (17) Å. The bpy ligands are bent, due to inter-ligand steric inter­actions between H atoms of opposite pyridyl units across the Ru center. The crystal structure exhibits an extensive hydrogen-bonding network involving the water ligands and the trifluoromethane­sulfonate counter-ions within two-dimensional layers, although no close hydrogen-bond inter­actions exist between different layers

μ-2,3,5,6-Tetrakis(pyridin-2-yl)pyrazine-bis[(2,2′:6′,2′′-terpyridine)ruthenium(II)] tetrakis(hexafluoridophosphate) acetonitrile tetrasolvate

In the title compound [Ru2(C15H11N3)2(C24H16N6)](PF6)4·4CH3CN, two of the counter-ions and one of the solvent molecules are disordered with occupancies for the major components between 0.57 (2) and 0.64 (1). The structure of the dinuclear tetracation exhibits significant distortion from planarity in the bridging 2,3,5,6-tetrakis(pyridin-2-yl)pyrazine (tppz) ligand, which has a saddle-like geometry with an average dihedral angle of 42.96 (18)° between adjacent pyridine rings. The metal–ligand coordination environment is nearly equivalent for the two RuII atoms, which have a distorted octahedral geometry due to the restricted bite angle [157.57 (13)–159.28 (12)°] of their two mer-arranged tridendate ligands [2,2′:6′,2′′-terpyridine (tpy) and tppz] orthogonal to each other. At the peripheral tpy ligands, the average Ru—N bond distance is 2.072 (4) Å for the outer N atoms trans to each other (Nouter) and 1.984 (1) Å for the central N atoms (Ncentral). At the bridging tppz ligand, the average metal–ligand distances are significantly shorter [2.058 (4) Å for Ru—Nouter and 1.965 (1) Å for Ru—Ncentral] as a result of both the geometric constraints and the stronger π-acceptor ability of the pyrazine-centered bridge. The dihedral angle between the two tpy planes is 27.11 (6)°. The intramolecular linear distance between the two Ru atoms is 6.6102 (7) Å

Self-assembly of supramolecular platinum complexes with bis-4-pyridyl cavitands

The design and self-assembly of six new supramolecular complexes (four triangles and two 2+2 assemblies) are described. These assemblies incorporate two new bispyridyl cavitand building blocks and were prepared in excellent yields (85-95%). The assemblies and building blocks were characterized with multinuclear NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis. Isotopically resolved mass spectrometry along with NMR data confirms the existence of the six assemblies

Electronic structure of the water oxidation catalyst cis, cis -[(bpy) 2(H 2O)Ru IIIORu III(OH 2)(bpy) 2] 4+, the blue dimer

The first designed molecular catalyst for water oxidation is the "blue dimer", cis,cis-[(bpy) 2(H 2O)Ru IIIORu III(OH 2)(bpy) 2] 4+. Although there is experimental evidence for extensive electronic coupling across the μ-oxo bridge, results of earlier DFT and CASSCF calculations provide a model with magnetic interactions of weak to moderately coupled Ru III ions across the μ-oxo bridge. We present the results of a comprehensive experimental investigation, combined with DFT calculations. The experiments demonstrate both that there is strong electronic coupling in the blue dimer and that its effects are profound. Experimental evidence has been obtained from molecular structures and key bond distances by XRD, electrochemically measured comproportionation constants for mixed-valence equilibria, temperature-dependent magnetism, chemical properties (solvent exchange, redox potentials, and pK a values), XPS binding energies, analysis of excitation-dependent resonance Raman profiles, and DFT analysis of electronic absorption spectra. The spectrum can be assigned based on a singlet ground state with specific hydrogen-bonding interactions with solvent molecules included. The results are in good agreement with available experimental data. The DFT analysis provides assignments for characteristic absorption bands in the near-IR and visible regions. Bridge-based dπ → dπ* and interconfiguration transitions at Ru III appear in the near-IR and MLCT and LMCT transitions in the visible. Reasonable values are also provided by DFT analysis for experimentally observed bond distances and redox potentials. The observed temperature-dependent magnetism of the blue dimer is consistent with a delocalized, diamagnetic singlet state (dπ 1*) 2 with a low-lying, paramagnetic triplet state (dπ 1*) 1(dπ 2*) 1. Systematic structural-magnetic-IR correlations are observed between ν sym(RuORu) and ν asym(RuORu) vibrational energies and magnetic properties in a series of ruthenium-based, μ-oxo-bridged complexes. Consistent with the DFT electronic structure model, bending along the Ru-O-Ru axis arises from a Jahn-Teller distortion with Ru-O-Ru dictated by the distortion and electron-electron repulsion. © 2012 American Chemical Society.Fil: Jurss, Jonah W.. University of North Carolina; Estados UnidosFil: Concepcion, Javier J.. University of North Carolina; Estados UnidosFil: Butler, Jennifer M.. Los Alamos National Laboratory; Estados UnidosFil: Omberg, Kristin M.. Los Alamos National Laboratory; Estados UnidosFil: Baraldo Victorica, Luis Mario. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Los Alamos National Laboratory; Estados UnidosFil: Thompson, Darla Graff. Los Alamos National Laboratory; Estados UnidosFil: Lebeau, Estelle L.. Los Alamos National Laboratory; Estados UnidosFil: Hornstein, Brooks. Los Alamos National Laboratory; Estados UnidosFil: Schoonover, Jon R.. Los Alamos National Laboratory; Estados UnidosFil: Jude, Hershel. Los Alamos National Laboratory; Estados UnidosFil: Thompson, Joe D.. Los Alamos National Laboratory; Estados UnidosFil: Dattelbaum, Dana M.. Los Alamos National Laboratory; Estados UnidosFil: Rocha, Reginaldo C.. Los Alamos National Laboratory; Estados UnidosFil: Templeton, Joseph L.. University of North Carolina; Estados UnidosFil: Meyer, Thomas J.. University of North Carolina; Estados Unido

Electronic Structure of the Water Oxidation Catalyst <i>cis</i>,<i>cis</i>-[(bpy)₂(H₂O)Ru^IIIORu^III(OH₂)(bpy)₂]⁴⁺, The Blue Dimer

The first designed molecular catalyst for water oxidation is the “blue dimer”, <i>cis</i>,<i>cis</i>-[(bpy)₂(H₂O)­Ru^IIIORu^III(OH₂)­(bpy)₂]⁴⁺. Although there is experimental evidence for extensive electronic coupling across the μ-oxo bridge, results of earlier DFT and CASSCF calculations provide a model with magnetic interactions of weak to moderately coupled Ru^III ions across the μ-oxo bridge. We present the results of a comprehensive experimental investigation, combined with DFT calculations. The experiments demonstrate both that there is strong electronic coupling in the blue dimer and that its effects are profound. Experimental evidence has been obtained from molecular structures and key bond distances by XRD, electrochemically measured comproportionation constants for mixed-valence equilibria, temperature-dependent magnetism, chemical properties (solvent exchange, redox potentials, and p<i>K</i>_a values), XPS binding energies, analysis of excitation-dependent resonance Raman profiles, and DFT analysis of electronic absorption spectra. The spectrum can be assigned based on a singlet ground state with specific hydrogen-bonding interactions with solvent molecules included. The results are in good agreement with available experimental data. The DFT analysis provides assignments for characteristic absorption bands in the near-IR and visible regions. Bridge-based dπ → dπ* and interconfiguration transitions at Ru^III appear in the near-IR and MLCT and LMCT transitions in the visible. Reasonable values are also provided by DFT analysis for experimentally observed bond distances and redox potentials. The observed temperature-dependent magnetism of the blue dimer is consistent with a delocalized, diamagnetic singlet state (dπ₁*)² with a low-lying, paramagnetic triplet state (dπ₁*)¹(dπ₂*)¹. Systematic structural–magnetic–IR correlations are observed between ν_sym(RuORu) and ν_asym(RuORu) vibrational energies and magnetic properties in a series of ruthenium-based, μ-oxo-bridged complexes. Consistent with the DFT electronic structure model, bending along the Ru–O–Ru axis arises from a Jahn–Teller distortion with ∠Ru–O–Ru dictated by the distortion and electron–electron repulsion