Polythiophene Hybrids of Transition-Metal Bis(salicylidenimine)s: Correlation between Structure and Electronic Properties.

The synthesis, electrochem., and spectroscopic behavior of tetradentate bis(salicylidenimine) transition metal complexes are reported. Appending these complexes with 3,4-ethylenedioxythiophene (EDOT) moieties allows for electrochem. polymn. at much lower potentials than the parent SALEN complexes. The resulting polymers display well-defined org.-based electrochem. at potentials <0.5 V vs. Fc/Fc+. The EDOT-modified N,N'-ethylene bis(salicylidene), N,N'-o-phenylene bis(salicylidene), and N,N'-trans-cyclohexylene bis(salicylidene) complexes I and II, III and IV, and V and VI, resp., display cyclic voltammograms with four org.-based redox waves. Increasing the interchain sepn. through the use of nonplanar bis(salicylidene) ligands results in only two redox waves. The cond. of the copper-based polymers decreases with increasing interchain spacing, with the max. cond. being 92 S cm-1 for poly(I) and 16 S cm-1 for the stilbenediamine complex polymer. The nickel complexes were less sensitive to increased interchain sepn. and showed cond. greater than 48 S cm-1 regardless of interchain spacing and near 100 S cm-1 in the case of poly(IV). In situ spectroelectrochem. was consistent with the segmented electronic nature of these polymers. Cyclic voltammetry of an analogous uranyl complex revealed that two electrons per repeat unit were removed during oxidn. From electrochem. and in situ EPR spectroscopic studies suggest that $π$-aggregation processes take place in those polymers in which close interchain spacing is allowed. [on SciFinder(R)]