Chiral Polymer Electrodes

[摘要] When (+/-)-[Ru(bipy)2(vbpy)]2+ is electrochemically scanned through the potentials -1.00V to -2.05V vs. Ag/AgNO3 in acetonitrile, electropolymerisation occurs and a polymer layer is formed on the working electrode of the electrochemical cell. This polymer modified electrode can be immersed in a solution of tartaric acid in water and conditioned so that subsequent immersions will produce (a) peaks immediately when the tartaric acid is of the same "hand", (b) no peaks immediately when the tartaric acid is of the opposite hand (although peaks will gradually appear over time and the electrode system will now behave with the opposite handed characteristics), or (c) reduced peaks immediately when the tartaric acid has partially the hand used in the conditioning process (In this system, as with (b), the electrode will behave as if it was conditioned with this solution if it is left to soak too long). If the polymer grown is poly-(-)-[Ru(bipy)2(vbpy)]2+ then the above results do not hold. This polymer will have a fixed helicity and as such will be unable to have further chiral structuring induced in it. Since this further chiral structuring is the prerequisite for the chiral sensing, these electrodes can not be used for such processes. The peaks at +0.45V and +0.65V vs. SSCE still show up with this system since loose bonding (although no restructuring) occurs. The actual chemical process involved is as follows: (i) The RuII of the polymer is oxidised to RuIII. (ii) This catalyses the oxidation of the tartrate. (iii) The tartrate or the tartrate oxidation product exchanges with the PF6- or the BF4- of the polymer. (iv) This results in the peaks at +0.65V and +0.45V. For poly-(+/-)-[Ru(bipy)2(vbpy)]2+, reaction (iii) induces chiral structuring whereas in poly-(-)-[Ru(bipy)2(vbpy)]2+, reaction (iii) does not induce chiral structuring and in fact occurs less strongly for this reason.

[发布机构] University:University of Glasgow

[关键词] Polymer chemistry