Patterned redox arrays of polyarylamines: I.: Synthesis and electrochemistry of a p-phenylenediamine and arylamino-appended p-phenylenediamine arrays

The synthesis of tetra-p-anisyl-p-phenylenediamine (TAPD, 1) and its derivatives containing appended diarylamino (AA) redox groups (2AA/PD, 2 and 4AA/1PD, 3) is presented. Such mixed redox arrays are of interest in a materials context for their projected directional electron transport properties and potential charge-trapping properties. Redox array 3 has a shell/core structure in which the four AA groups of higher oxidation potential surround a central p-phenylenediamine (PD) group of lower oxidation potential. Electrochemical characterization of these substrates is reported, and the redox gradients in arrays 2 and 3 are estimated to be similar to0.2 V. The meta-linked AA and PD groups of 2 and 3 are observed to be weakly electronically coupled. EPR and electrochemical data show 2(+.) and 3(+.) to be PD-localized radical cations (i.e., 2AA/PD+. and 4AA/PD+., respectively). Despite AA shielding of the core PD group in 3, its solution-phase cyclic voltammogram appears to be normal, indicating relatively facile heterogeneous electron transfer at the electrode surface/solution interface under ambient conditions. The radical cations of 1-3 are prepared as robust, isolable salts. Finally, evidence for intervalent charge transfer is found in the near-IR spectra of 2(+.) and 3(+.).