SYNTHESIS, ELECTROOXIDATION, AND CHARACTERIZATION OF BIS(DIPHENYLAMINE)NAPHTHALENE DIIMIDE

We have synthesized a new poly(imide) precursor for solution electrode position onto conducting surfaces. The new monomer, lamino(phenyl)]-1, 4,5,8-naphthalenetetracarboxylic diimide (DNTD), contains a central na phthalene diimide moiety flanked by two dimerizable diphenylamine grou ps. DNTD was oxidatively electrodeposited onto Au-, Pt-, and In-doped SnO2 surfaces from DMSO, CH3CN, and CH2Cl2. The cyclic voltammetry is consistent with initial radical cation formation of diphenylamine grou ps, and then para C-C coupling of radicals to form dimers and higher o rder oligomers. IR spectroscopy was used to determine the average degr ee of polymerization and confirm para coupling. The resulting material shows electrochemically reversible 1e(-)/ and 2e(-)/monomer unit redu ction waves corresponding to the naphthalene tetracarboxylic diimide r adical anion and dianion. Also a quasireversible 1e(-)/ and 2e(-)/mono mer unit oxidation corresponding to the oxidation of diphenylbenzidine unit is shown. Visible-NIR spectroelectrochemistry shows low-energy a bsorptions in the NIR (similar to 1100 nm) corresponding to diphenylbe nzidine radical cation pi-dimer in CH2Cl2 whereas in DMSO and CH3CN at the same potential, no low-energy bands are observed. Variable-angle transmission spectroscopy on air-oxidized dry films prepared from CH2C l2 shows band shifts from 1100 to 950 nm and almost no shift of the 84 5 nm band of films formed in DMSO. This is consistent with the anisotr opic nature of the material from CH2Cl2. We interpret these spectra as arising from pi-stacks parallel to the surface. Scanning electron mic rographs show small domains (similar to 300-500 nm) for films composed mostly of dimers and smooth films for relatively higher molecular wei ght materials.