Theoretische und experimentelle Hinweise auf einen neuen Typ spingekoppelter Singulett‐Spezies: isomere gemischtvalente Komplexe mit verbrückendem Radikalanion‐Liganden

Abstract

Eine eigentümliche Elektronenstruktur, (Mn+0.5)(μ‐L.−)(Mn+0.5), wie sie zuvor nur im Zusammenhang mit Metall‐Ligand‐Charge‐Transfer‐angeregten Zuständen diskutiert worden war, konnte strukturell und über quantenchemische Analyse der rac‐ (siehe Bild) und meso‐Isomere von [(μ‐abpy){Ru(acac)2}2] (abpy=2,2′‐Azobispyridin, acac−=Acetylacetonat) etabliert werden.

Multiple one-electron oxidation and reduction of trinuclear bis(2,4-pentanedionato)ruthenium complexes with substituted diquinoxalino[2,3-a:2′,3′-c]phenazine ligands

“…rather highly charged Ru II Ru III Ru III forms may reflect diminished Coulombic effects due to enhanced charge delocalization by the six p donating Cl (1 2+ ) or inductively electron donating Me substituents (2 2+ ). Not unexpectedly, the potentials for corresponding diastereoisomers are rather similar [3,18,19]. Nevertheless, the profile of the cyclic voltammograms, in particular for 2, suggests the existence of two diastereoisomers in solution as has also been observed by 1 H NMR (Fig.…”

Metal-Induced Reductive Ring Opening of 1,2,4,5-Tetrazines: Three Resulting Coordination Alternatives, Including the New Non-Innocent 1,2-Diiminohydrazido(2−) Bridging Ligand System

“…Even symmetrically dinuclear complexes of the described kind can exist as isomers due to the tris-chelate coordination at the metals . In structurally related cases such as {(μ-abpy)[Ru(bpy) 2 ] 2 } 4+ , the meso and rac isomers could be separated and identified on the basis of NMR spectroscopy, the recently obtained analogues (μ-abpy)[Ru(acac) 2 ] 2 could even be crystallized in both forms . The two crystallized compounds 1b and 3b in the present case contain meso-configured molecules (Figures and ); the rac forms are distinguished from the meso isomers mainly by a much larger difference (Δ) between the CH resonances of the acac - co-ligands (Δ meso = 0.2 ppm vs Δ rac = 0.7 ppm, see Figure and Experimental Section).…”

New Rare Earth Metal Complexes with Nitrogen‐Rich Ligands: 5,5′‐Bitetrazolate and 1,3‐Bis(tetrazol‐5‐yl)triazenate—On the Borderline between Coordination and the Formation of Salt‐Like Compounds

“…(14), O1-Eu1-N11 137.95 (12), O7-Eu1-N11 69.08(11), O3-Eu1-N11 132.48 (12), O5-Eu1-N21 70.50 (12), O6-Eu1-N21 140.53 (14), O2-Eu1-N21 68.97 (15); symmetry operation for equivalent atoms: i: 3Àx, 1Ày, 1Àz. (7), H031ÀN24 1.96(8), H032ÀN23 2.00(6), H2ÀN22 1.91(9); O1-H16-N12 172(5), O1-H24-N13 170 (7), O4-H9-N14 173 (7), O9-H22-N24 165(8), O8-H13-N23 154 (7), O2-H2-N22 172 (8).…”

“…[31] Relevant data concerning crystallographic data collection and refinement are compiled in Table 2. CCDC 660545 (1), 660546 (2), 660547 (3), 660548 (4), 660549 (5), 660550 (6), 660551 (7) and 660713 (9) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.…”

“…[6] From the viewpoint of coordination chemistry, they represent a very interesting class of ligands that are mainly characterised by their extremely low-lying p*-orbitals, which makes them excellent p-acceptors. [7] Such strong p-acceptor ligands were frequently used, for example, for the construction of complexes with interesting optical or electrochemical properties, with applications in non-linear optic (NLO) materials, [8] electronic devices (switches or wires) [9] or multielectron catalysis. [7c, 10] In transition-metal complexes, they are usually combined with electron-rich (low oxidation state), late transition metals of the d-block, such as Cu II , Re I or Ru II , allowing for rather stable as well as moisture and oxygen insensitive materials.…”