Synthesis and electropolymerization of bis (4-cyano-1-pyridino) alkanes: effect of co-and counter-ions
The six new bis(4-cyano-1-pyridino)alkanes derivatives with different alkyl chain length (n = 2-6) and cyanometallate anions ([Fe(CN)(6)](3) , [Co(CN)(6)](3) , [Fe(CN)(4)(CNH)(2)](2) and [Fe(CN)(6)](4) ) have been synthesized and characterized by 1H-NMR, single-crystal X-ray analysis and UV-vis spectroscopy. The electroreduction of the obtained compounds under potentiostatic conditions (E-1 = -0.75 V) and further electrode stabilization at E-2 = 0V resulted in the deposition of polyviologen films. The current efficiency of electropolymerization was found to increase with varying the counter anion in the row: [Fe(CN)(6)](3) < Br < [Co(CN)(6)](3) similar to [Fe(CN)(6)](4) . Analysis of cyclic voltammograms and EDX data demonstrated the simultaneous incorporation of [Fe(CN)(6)](4) and K+ ions into poly(pentyl-viologen) film during electropolymerization, and further expulsion of K+ ions during the film stabilization at E-2 = 0V. The electropolymerization efficiency was found to increase with increasing the alkyl chain length, resulting in the formation of polyviologen film with higher content of dimer form of viologen cation radical.