Polyterthiophene π-conjugated by organomolybdenum complex (II): electropolymerization of erythro-[(η5-C5H5)2Mo2(O)2(μ-O){μ-η2:η2-C(Ph)C[C4HS(C4H3S-2)2-2,5]}]

Terthiophene, to which the organomolybdenum oxide cluster complex is π-conjugated, erythro-[(η5-C5H5)2Mo2(O)2(μ-O){μ-η2:η2-C(Ph)C[C4HS(C4H3S-2)2-2,5]}] (2) was prepared by treatment of erythro-[(η5-C5H5)2Mo2(CO)4{μ-η2:η2-C(Ph)C[C4HS(C4H3S-2)2-2,5]}] (1) with air in the presence of trimethylamine N-oxide in 1:1 MeCN–CH2Cl2. The structure of 2 was identified by spectroscopic methods and elemental analysis. CV of 2 in TBAP–CH2Cl2 solution exhibits three discrete electrode processes. Two reversible processes, at Epa=0.89 and 1.08 V, are associated with the oxidation of the cluster core to the radical cation, [Mo2core]radical dot+ and dication, [Mo2core]2+, respectively. Irreversible process at Epa=1.30 V can be assigned to the terthiophene moiety. Electrochemically active, polymer film of 2 shows an electrochromic switching between shiny purple (undoped) and transparent blue (doped), which is sharply discerned form the color contrast of the typical polythiophenes as well as 1. Such a unique electrochormism can be ascribed to the direct π-electronic interaction between the conjugated organomolybdenum cluster and the polythiophene backbone.