Metal (Hg, Pt, Ru) Bisalkynyl Bridge between Tetrathiafulvalene Electrophores and Electronic Interplay

Abstract

A series of metal (Hg, Pt, Ru) bis(alkynyl-tetrathiafulvalene) complexes have been investigated to study the electronic interplay between the metal and the tetrathiafulvalene (TTF), as well as between the two peripheral TTF electrophores along the organometallic bridge. Cyclic voltammetry experiments, together with spectro-electrochemical investigations, have shown the electronic effect of the metal center through the linker on redox properties of the TTF, as well as the influence of the length of the conjugated organic linker. These data show that the degree of coupling can be modulated from no coupling with mercury to appreciable electronic coupling between different electrophores with ruthenium.

A Dibenzotetrathiafulvalene-Bridged Bis(alkenylruthenium) Complex and Its One- and Two-Electron-Oxidized Forms

“…Cathodic shifts of similar magnitude were previously observed in ruthenium complexes with one or two ethynyl-TTF ligands. 30,31,36 On the other hand, they are shifted to slightly or significantly more positive values than in the 1,4divinylphenylene-bridged diruthenium complex {Ru}-CH� CH-p-C 6 H 4 −CH�CH-{Ru} [Ph(ViRu) 2 ]. 72 The presence of three interlinked redox-active constituents, two of which are chemically different, in direct π conjugation renders an a priori assignment of the individual redox waves to any specific redox site impossible.…”

“…Best represented are ferrocenyl (Fc) derivatives with direct Fc-TTF connectivities or Fc-Arylene-TTF dyads. − In addition, the Lorcy group has published a series of elegant studies on ruthenium, platinum, and mercury complexes with one or two ethynyl-TTF or extended TTF (exTTF) ligands. Structures of the ruthenium complexes of relevance to the present work are summarized in Figure . − Mono- and bis-ethynyl (ex)­TTF ruthenium complexes possess a rich electrochemistry with one chemically reversible redox wave per Ru­(dppe) 2 and TTF constituent and significantly lower first oxidation potentials than any of their individual redox-active entities. Moreover, the unpaired spin densities and charge(s) of their one-electron-oxidized or one- and two-electron-oxidized forms are delocalized over all redox sites.…”