Multistep Oxidation of Diethynyl Oligophenylamine-Bridged Diruthenium and Diiron Complexes

Abstract

Homo-dinuclear nonlinear complexes [{M(dppe)Cp*}{μ-(-C≡C)X}] (dppe = 1,2-bis(diphenylphosphino)ethane; Cp* = η-CMe; X = triphenylamine (TPA), M = Ru (1a) and Fe (1b); X = N,N,N',N'-tetraphenylphenylene-1,4-diamine (TPPD), M = Ru (2a)) were prepared and characterized by H,C, and P NMR spectroscopy and single-crystal X-ray diffraction (1a, 2a). Attempts to prepare the diiron analogue of 2a were not successful. Experimental data obtained from cyclic voltammetry, square wave voltammetry, UV-vis-NIR (NIR = near-infrared) spectro-electrochemistry, and very informative IR spectro-electrochemistry in the C≡C stretching region, combined with density functional theory calculations, afford to make an emphasizing assessment of the close association between the metal-ethynyl termini and the oligophenylamine bridge core as well as their respective involvement in sequential one-electron oxidations of these complexes. The anodic behavior of the homo-bimetallic complexes depends strongly both on the metal center and the length of the oligophenylamine bridge core. The poorly separated first two oxidations of diiron complex 1b are localized on the electronically nearly independent Fe termini. In contrast, diruthenium complex 1a exhibits a significantly delocalized character and a marked electronic communication between the ruthenium centers through the diethynyl-TPA bridge. The ruthenium-ethynyl halves in 2a, separated by the doubly extended and more flexible TPPD bridge core, show a lower degree of electronic coupling, resulting in close-lying first two anodic waves and the NIR electronic absorption of [2a] with an indistinctive intervalence charge transfer character. Finally, the third anodic waves in the voltammetric responses of the homo-bimetallic complexes are associated with the concurrent exclusive oxidation of the TPA or TPPD bridge cores.

Highly conducting Wurster-type twisted covalent organic frameworks

“…26 They can be easily oxidized, generating stabilized radical cations within their π-systems. 27 The doping of this motif through oxidation is a well-studied feature, and the hereby generated radical cations show promising stability as conductive organic materials for charge transport or storage. [28][29][30] Organic salts based on TMPD as the electron donor and tetracyanoquinodimethane (TCNQ) as the electron acceptor show high electrical conductivities.…”

Role of Substituents at 3‐position of Thienylethynyl Spacer on Electronic Properties in Diruthenium(II) Organometallic Wire‐like Complexes

“…The lack of uniform distribution (compared to [5 a‐H] + ) of the spin‐density in complexes [5 b‐H] + to [5 e‐H] + indicates that mixed valence characteristics which generate from variation of electronic delocalization is consistent with the electrochemical data. Notably, Liu and co‐workers have also described unsymmetrical spin distribution and its effect on electronic properties by DFT studies in homo‐dinuclear ruthenium(II) complexes of type [M(dppe)Cp*−C≡C−X−C≡C‐>M(dppe)Cp*] (X=triphenylamine and N,N,N′,N′‐tetraphenylphenylene‐1,4‐diamine] …”

Modulation of Electrochemical and Spectroscopic Properties in Ru(II)‐Terpyridyl End‐Capped Homobimetallic Organometallic Complexes by Varying π‐Conjugated Organic Spacers

“…Hartl and Liu reported an interesting series of diruthenium(II) complexes and investigated their involvement in sequential one-electron oxidation mediated by oligoacene [45] and triphenyl amine. [46] bridges. Rigaut and coworkers reported a special category of ruthenium(II) binuclear wire-like complexes (RuC 12 Ru complex) with the remote metal termini connected by twelve carbon atoms, exhibiting a substantial long-range coupling between the two metal termini with K c in the order of 10 4 .…”

“…The homobimetallic diruthenium mixed-valence complexes linked by π-conjugated alkynyl organic spacers often exhibit strong electronic communication due to the good stability of Ru II …Ru III mixed-valence states. [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] The synthesis and application of various binuclear ruthenium-alkynyl complexes supported by different π-conjugated bridging ligands have been studied by various research groups in order to investigate the role of bridging units as well as the ancillary ligands. Chen and coworkers developed a series of rod-like diruthenium complexes with various metal termini such as [(bph…”