Substituent and Solvent Effects on the Electrochemical Properties and Intervalence Transfer in Asymmetric Mixed‐Valent Complexes Consisting of Cyclometalated Ruthenium and Ferrocene

Abstract

Four heterodimetallic complexes [Ru(Fcdpb)(L)](PF6) (Fcdpb=2-deprotonated form of 1,3-di(2-pyridyl)-5-ferrocenylbenzene; L=2,6-bis-(N-methylbenzimidazolyl)-pyridine (Mebip), 2,2':6',2''-terpyridine (tpy), 4-nitro-2,2':6',2''-terpyridine (NO2tpy), and trimethyl-4,4',4''-tricarboxylate-2,2':6',2''-terpyridine (Me3tctpy)) have been prepared. The electrochemical and spectroelectrochemical properties of these complexes have been examined in CH2Cl2, CH3NO2, CH3CN, and acetone. These complexes display two consecutive redox couples owing to the stepwise oxidation of the ferrocene (Fc) and ruthenium units, respectively. The potential difference, ΔE(1/2)(E(1/2)(Ru(II/III))-E(1/2)(Fc(0/+))), decreased slightly with increasing solvent donocity. The mixed-valent states of these complexes have been generated by electrolysis and the resulting intervalence charge-transfer (IVCT) bands have been analyzed by Hush theory. Good linear relationships exist between the energy of the IVCT band, E(op), and ΔE(1/2) of four mixed-valent complexes in a given solvent.

Synthesis, Electrochemistry, and Optical Properties of Half‐Sandwich Ruthenium Complexes Bearing Triarylamine‐Anthracenes

“…Within the spectra, an absorption band could be observed at 1195 nm, which is a typical range for charge‐transfer excitations. Compared to other IVCT bands in unsymmetrical mixed‐valent systems, and ruthenium/iron half‐sandwich aryl alkynes, , the observed intensity of the charge‐transfer excitation is rather high (4150 L mol –1 cm –1 ) with a small FWHM (full width at half maximum, Δν̃ 1/2 ) of 2090 cm –1 which hints at a considerable degree of delocalization , . The IVCT band of 4 + is red‐shifted compared to related (symmetrical) bi‐ and trinuclear complexes and shows lower intensities , , .…”

Influence of the electronic effect of an ancillary ligand on MMCT and LMCT in localized cyanide-bridged complexes containing non-innocent ligands

“…[18][19][20][21][22][23][24][25][26] Cyanide-bridged MV complexes occupy an important position in the investigation of electronic transition due to the excellent electron transfer ability of the cyanide bridge. 27,28 To date, numerous cyanidebridged MV complexes with M II -CN-M III (M = Ru, Fe) and their MMCT properties have been synthesized and investigated. [29][30][31][32][33][34][35][36][37][38] On the other hand, metal complexes with non-innocent ligands have attracted considerable interest since Jørgensen first mentioned the expression "non-innocent" in 1966.…”

“…18–26 Cyanide-bridged MV complexes occupy an important position in the investigation of electronic transition due to the excellent electron transfer ability of the cyanide bridge. 27,28 To date, numerous cyanide-bridged MV complexes with M II –CN–M III (M = Ru, Fe) and their MMCT properties have been synthesized and investigated. 29–38…”

Synthesis, Structure, Electrochemical, and Spectroscopic Properties of Hetero-Bimetallic Ru(II)/Fe(II)-Alkynyl Organometallic Complexes

“…The pioneering discovery of Creutz–Taube ion, [(NH 3 ) 5 Ru-pyrazine-Ru­(NH 3 ) 5 ] 5+ , led the scientists to design and develop binuclear complexes to examine the extent of charge delocalization in their mixed-valence states and its fascinating spectroscopic properties . Homobimetallic complexes capable of imparting remote metal–metal communication across the bridging ligand often generate stable mixed-valence systems and can be coined as molecular wires . , More interestingly, special attention has been devoted on the heterobimetallic molecular wires having intrinsically redox asymmetry of the metal centers. , Among the heterobimetallic complexes, introduction of ferrocenyl (Fc) acetylide gives a wide diversity of the heterobimetallic complexes which are advantageous for long-range electron transfer. ,− The synthesis and application of such linear ferrocenyl acetylide end-capped heterobimetallic complexes, supported by different metal centers, have been developed by various research groups. ,− Sato and co-workers reported [(η 5 -Cp)­(PP) 2 Ru­(II)-CC-Fc], while Bruce developed [η 5 -Cp*­(PP)­M­(II)-CC-Fc] (M = Ru, Os; PP = (PPh 3 ) 2 , dppe or dppf; Cp = C 5 H 5 , Cp* = C 5 Me 5 ) based heterobimetallic complexes to investigate electrochemical communication between Fe­(II) and Ru­(II)/Os­(II) termini. , Long and co-workers have developed a series of heterobimetallic bis­(acetylide) ferrocenyl complexes capped with Ru­(II)­(dppm) 2 [dppm = 1,2-bis­(diphenyl­phosphino)­methane] by varying the electronic nature of the aromatic acetynyl ligands, and the electrochemical properties have been studied . Jia and co-workers reported heterobimetallic ferrocene-ruthenium­(II) complexes, [Fc­(CHCH) 3 RuCl­(CO)­(PhPy)­(PPh 3 ) 2 ] showing two partially reversible redox waves for one electron oxidation of the ferrocenyl moiety and the ruthenium­(II) metal center, respectively .…”