Synthesis, Characterization, and Electrochemical Properties of Diruthenium Complexes Bridged by Anthraquinones

Abstract

We have prepared four isomeric binuclear ruthenium complexes, in which two ruthenium units have been attached to the 1,4-(4a), 1,5-(4b), 1,8-(4c), or 2,6-positions (4d) of a central anthraquinone (Aq) moiety, leading to packed (4c) or extended (4a,b,d) topologies. All of these bimetallic complexes were fully characterized by elemental analysis, 1 H, 13 C{ 1 H}, and 31 P NMR{ 1 H} spectrometry, and UV/vis spectrophotometry. Moreover, the structures of 4a,b were established by X-ray crystallography. The electrochemical properties of the stable binuclear ruthenium complexes 4aÀd were investigated, revealing that the two metal centers in 4aÀc could interact with each other through an anthraquinone bridge, suggesting that the electron-withdrawing carbonyl chain actually functions as an effective bridge.

Conformational Tuning of the Intramolecular Electronic Coupling in Molecular‐Wire Biruthenium Complexes Bridged by Biphenyl Derivatives

“…The synthesis of 3a-e required two steps from 4,4'-diiodo biphenyls 1a-e,w hichp roceeded in 58-74 %o verall yield:[ (PPh 3 ) 2 PdCl 2 ]/CuI-catalyzed coupling with trimethylsilylacetylene affording 4,4'-bis(trimethylsilylethynyl)b iphenyls 2a-e,a nd KOH/MeOH-mediated cleavage of the protecting groups.D iethynyl biphenyls 3a-e were treated with the ruthenium hydride complex [RuHCl(CO)(PPh 3 ) 3 ]t og ive the corresponding insertion products [{(PPh 3 ) 2 Cl(CO)Ru} 2 (m-CH=CHÀ BiphÀCH=CH)],w hich were not isolated because these five-coordinate complexesw ere air-sensitive, especially in solution. [21] Hence, PMe 3 was added directly to give the corresponding sixcoordinate complexes 4a-e,w hich were characterized by 1 H, 13 Ca nd 31 PN MR spectroscopy.T he 1 HNMR spectra (in CDCl 3 ) of 4a-e featured RuÀCH signals at about 8.1 ppm, and the signal for b-CH of the vinyl group was at about 6.6 ppm. These chemicals hifts are close to those found in complexes [RuCl (CO)(PMe 3 ) 3 ] 2 (CH=CH) n .…”

“…The large number of compounds that has been synthesized allows the study of variousf actors, including distance, solvent effect, molecular topology,m etal complex, the nature of the bridge, and tuning the degree of charge delocalization between the terminal redox sites in the MV state. [21][22][23][24][25][26][27][28][29][30][31][32][33] Since the bridging ligands play an important role in tuning the ET properties of MV complexes, ranging from localization to delocalization, the synthesis of such compounds with various bridgingl igands has attracted considerable interest. [19] Recently,a ni mportant aspect of developing the [ML n (bridge)ML n ] system is controlling the electronic delocalization in the ground state of the MV form and the metal-versus-ligand character of the redox processes to yield am etal-centered or bridge-centered process.…”

Synthesis, Characterization, and Properties of Anthracene-Bridged Bimetallic Ruthenium Vinyl Complexes [RuCl(CO)(PMe3)3]2(μ-CH═CH-anthracene-CH═CH)

“…9b In our recent work, we reported a series of anthracene quinone based bimetallic ruthenium vinyl complexes (Scheme 1), in which the ruthenium atoms were attached at the 1,4-, 1,5-, 2,6-, and 1,8-positions of the anthracene quinone. 11 The electrochemical properties of these complexes showed that the interaction between the two metal centers was not very obvious. This research inspired us to explore the properties of 9,10-, 1,5-, 2,6-, and 1,8-disubstituted anthracene bimetallic ruthenium vinyl complexes.…”

“…In addition, the other broad absorption bands of complexes 1aÀd at 400À500 nm can be attributed to MLCT (metal-to-ligand charge transfer), which is similar to that for bimetal complexes of anthraquinone-based bridging ligands. 11 Subsequently, the fluorescence properties of complexes 1aÀd were investigated in dichloromethane solution (2 Â 10 À5 mol/ L) at room temperature. From the fluorescence properties of complexes 1aÀd shown in Figure 3B, it can be seen that the complexes 1a,b,d displayed very weak fluorescence.…”

“…We also found that these anthracene-based ruthenium vinyl complexes had better electronic communication in comparison with the anthracene quinone based ruthenium vinyl complexes described in our previous report. 11 This can be attributed to two reasons: one is that the electron-withdrawing carbonyl decreases the electronic interaction between the two metal centers and the other is that, according to the crystal structures of two series of bimetal complexes, the rigidity and coplanarity of the anthracene bridging ligand are stronger than those of the anthraquinone bridging ligand and lead to increasing interaction between the two metal centers.…”