Oxo-Centered Mixed-Ligand Triruthenium Complexes Having Redox-Active N-Methyl-4,4‘-bipyridinium Ions (mbpy⁺). Reversible Multistep Electrochemical Properties of [Ru^III₂Ru^II(μ₃-O)(μ-CH₃CO₂)₆(mbpy⁺)₂(CO)]²⁺ and [Ru^III₃(μ₃-O)(μ-CH₃CO₂)₆(mbpy⁺)₂(L)]³⁺ (L = H₂O and N-Het

Abstract

A new series of oxo-centered acetate-bridged triruthenium comlexes having two redox-active N-methyl-4,4'-bipyridinium ions (mbpy(+)) have been prepared, and their reversible multistep and multielectron electrochemical properties are reported: [Ru(III)(2)Ru(II)(&mgr;(3)-O)(&mgr;-CH(3)CO(2))(6)(mbpy(+))(2)(CO)](2+) and [Ru(III)(3)(&mgr;(3)-O)(&mgr;-CH(3)CO(2))(6)(mbpy(+))(2)(L)](3+) (L = H(2)O, pyrazine (pz), pyridine (py), imidazole (Him), and 4-(dimethylamino)pyridine (dmap)). Among these series, the CO complex, [Ru(III)(2)Ru(II)(&mgr;(3)-O)(&mgr;-CH(3)CO(2))(6)(mbpy(+))(2)(CO)](ClO(4))(2).2DMF (1b.2DMF) was structurally characterized by X-ray crystallography. 1b.2DMF crystallizes in the monoclinic space group P2(1)/m (No. 11) with a = 8.740(6) Å, b = 32.269(6) Å, c = 10.276(4) Å, beta = 103.37(5) degrees, V = 2820(2) Å(3), Z = 2, d(calcd) = 1.636 g cm(-)(3), and R = 0.071 (R(w) = 0.074) for 5277 independent reflections (|F(o)| > 3sigma(|F(o)|). The (CO)Ru.Ru distance (3.410(2) Å) is appreciably longer than the other Ru.Ru distance (3.276(2) Å), indicating that the trinuclear core is in the valence-trapped Ru(III)(2)Ru(II)(CO) oxidation state. The cyclic voltammogram of [Ru(III)(2)Ru(II)(&mgr;(3)-O)(&mgr;-CH(3)CO(2))(6)(mbpy(+))(2)(CO)](PF(6))(2) (1a) shows a total of seven reversible one-electron redox steps at E(1/2) = +0.90, +0.26, -1.07, -1.17, -1.56, -1.97, and -2.32 V and one irreversible step at E(pc) = -2.99 V vs Fc/Fc(+) in a 0.1 M [(n-C(4)H(9))(4)N]PF(6)-CH(3)CN solution (M = mol dm(-)(3)). All of the waves are clearly assignable to the triruthenium "Ru(3)(&mgr;(3)-O)" core-based or mbpy(+) ligand-based processes. The splitting of each ligand-based redox processes (mbpy(+)/mbpy(*) and mbpy(*)/mbpy(-)) into two one-electron steps indicates that electronic interactions between two terminal ligands occur through the triruthenium cluster core. Other mixed-ligand Ru(III)(3) analogs also show multistep redox behavior involving a total of eight or nine electrons. While the extent of interactions between ligands is much smaller than that found in the CO complex, it is systematically changed by the nature of L; with more basic L, interactions between two mbpy(+) ligands become larger.

TOTAL ASSIGNMENT OF 1H AND 13C NMR SPECTRA OF A BRIDGED TRIRUTHENIUM CLUSTER-POLYPYRIDINE DIMER BASED ON 2D (COSY, HMQC, AND HMBC) TECHNIQUES

“…Expanded segments of13 C NMR spectrum of the dimer[Ru 3 O(CH 3 COO)6 (py) 2 (tmbpy)Ru(bpy) 2 (Cl)](PF 6 ) 2 in CD 3 CN solution. S = solvent peak.…”

Trinuclear Ruthenium Clusters as Bivalent Electrochemical Probes for Ligand–Receptor Binding Interactions

“…The observed E 1/2 values are similar to those reported in the literature for similar trinuclear ruthenium clusters. 44, 50, 71–78 ΔE p (E a −E c ) was observed to be, on average, 65 mV for each cluster studied, indicative of a reversible electrochemical couple. 79 The current ratio of (i a /i c ) was typically approximately 0.7.…”

“…4, 80 E 1/2 values of the trinuclear ruthenium clusters were similar to those observed for analogous complexes reported in the literature. 44, 50, 71–78 A representative CV is shown in Figure 4 for the bivalent cluster, 9 .…”

“…50 In order to evaluate the atomic charges and the force constants, a quantum mechanical (QM) calculation was carried out to optimize the geometry of the cluster. Calculations were performed using the Jaguar 7.7 package implemented in Schrodinger 9.1.…”

A pyrazine‐bridged trimer of oxo‐centered triruthenium–carbonyl clusters and the supramolecular assembly built from multiple noncovalent contacts

“…As the overall complex is neutral, each [Ru 3 O(EtCOO) 6 (CO)] core formally contains a mixed‐valent Ru II Ru III Ru III state, in which low‐valent +II is stabilized at Ru attached to CO as a result of π‐back bonding in the Ru–CO moiety. Earlier reports have addressed the valence‐localized nature of the triruthenium–carbonyl derivatives [Ru 3 O(RCOO) 6 (CO)L 2 ] with various peripheral ligands L and carboxylates (RCOO − ) on the basis of structures [ 37 ] and spectroscopic data, including Fourier‐transform infrared (FT‐IR) [ 38 ] and extended X‐ray absorption fine structure (EXAFS) data. [ 39 ] Ligand‐exchange kinetic study on [Ru 3 O(CH 3 COO) 6 (CO)(pyridine) 2 ] and [Ru 3 O(CH 3 COO) 6 (pyridine) 3 ] 0/1+ in CD 3 CN also led to the same conclusion—that the carbonyl triruthenium cluster is described as valence‐trapped.…”