Synthesis, structure and electrochemistry of mononuclear and dinuclear ruthenium–thiophenecarboxylate complexes

Three 3-thiophenecarboxylate-containing and one 2,2′-bithiophene-5-carboxylate-containing diruthenium complexes, [Ru2(μ-O2CR)4(MeOH)2]PF6 (R = –C4H3S 1, –CH2C4H3S 2, –CHCHC4H3S 3 and –C8H5S24), were prepared using a facile carboxylate exchange reaction and characterized using elemental analysis, IR and UV–Vis spectroscopy. “Disassembly” of complexes 1–4 using 1,2-bis(diphenylphosphino)-ethane (dppe) yielded the mononuclear ruthenium(II) complexes, [Ru(η2-O2CR)(dppe)2]PF6 (R = –C4H3S 5, –CH2C4H3S 6, –CHCHC4H3S 7 and –C8H5S28), which were characterized as above as well as by 1H and 31P NMR and single crystal X-ray analysis. All of the complexes were studied using cyclic voltammetry to assess the ability of the thiophene moieties to undergo oxidative polymerization with complex 4 showing the greatest promise.

Graphical abstractDinuclear diruthenium(II,III)-tetra-3-thiophenecarboxylate and -tetra-2,2′-bithiophene-5-carboxylate complexes of the form [Ru2(μ-O2CR)4(MeOH)2]PF6 and mononuclear ruthenium(II)-3-thiophenecarboxylate and -2,2′-bithiophene-5-carboxylate complexes of the form [Ru(dppe)2(η2-O2CR)]PF6 (where dppe = 1,2-bis(diphenylphosphino)ethane and R = –C4H3S, –CH2C4H3S, –CHCHC4H3S and –C8H5S2) were synthesized and characterized. The mononuclear complexes were studied using X-ray diffraction and the oxidative polymerization of the thiophene groups on all of the complexes was assessed via cyclic voltammetry.Figure optionsDownload full-size imageDownload as PowerPoint slide