The preparation of polymer-modified electrodes that function as electrocatalysts, chemical sensors, and electrochromic displays remains an active field of research.[1] We are currently engaged in the design of new conducting polymer architectures containing transition metals in welldefined coordination environments. [2] Our interest in these materials is motivated by the wealth of desirable characteristics endowed by transition metals for the development of sensory materials that should be responsive to anions, Lewis bases, and small molecules (CO, O 2 , NO, etc.). [3,4] Polymers based on transition metal±containing N,N¢-ethylenebis(salicylidenimine) (salen) complexes have been previously prepared by the oxidative polymerization of monomeric M(salen) complexes.[5] In all but a few of these polymers, [5d,5j] the electrochemistry of the films displays ligand-based redox processes at high potentials that are considerably removed from the expected metal-based electroactivity. These films generally lacked metal-centered electroactivity; however, thin Co(salen) films did display redox processes attributed to the Co 2+/3+ couple, which diminished as the films became progressively thicker.[5d] We have targeted conducting polymers that incorporate the metal centers as part of the conduction pathway and tightly couple the conductivity to the redox characteristics of the metal center. We believe that an organic polymer redox potential that is the same or below that of the metal center should create materials with enhanced electron mobilities, and thereby form optimized sensory and catalytic materials.In this contribution we demonstrate that tuning the redox potential of the organic polymer backbone to be similar to that of the Co 2+/3+ redox potential creates enhanced electroactivity of cobalt centers embedded in the polymer backbone. This intimate coupling of the metal and polymer in the conduction process can impart sensitivity to specific analytes, and we further demonstrate that Lewis bases such as pyridine and substituted pyridines affect the polymers' conductivity.To generate the maximum interaction between thiophene moieties and the cobalt centers we designed salen complexes with a para relationship between phenolic oxygens and the thiophenes. The monomer ligands, 2 and 5, were produced by palladium-catalyzed Stille coupling methods (Scheme 1) followed by condensation with ethylenediamine.[6a] Monomeric cobalt complexes 3 and 6 were prepared by standard methods [6b] as black microcrystals from dimethylformamide (DMF) solutions under argon. Polymeric films of 3 can be readily oxidatively deposited on platinum electrodes from a saturated monomer solution ([3] ca. 0.1 mM) in 0.1 M Bu 4 NPF 6 /MeCN by scanning between ±0.75 V and 0.85 V (Fig. 1).[7] The cyclic voltammogram (CV) of a very thin film of poly(3) reveals that the ratio of metal-to organic-centered redox waves is approximately 1:2 (Fig. 2a). Upon growing a film sufficiently thick to connect two interdigitated electrodes, we see that the wave attributed ...

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Polythiophene−transition metal hybrid materials based on cobalt salen have been prepared and shown to catalyze the reduction of O2. The conjugated nature of the polymer backbone allows for facile electron transfer from the polymer surface to the active metal centers to affect this reduction. Rotating ring−disk measurements show only minute amounts of H2O2, indicating a selective reduction of O2 to H2O.

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