Ladder Oligo(m-aniline)s: Derivatives of Azaacenes with Cross-Conjugated [pi]-Systems
- UNL
We describe the synthesis and electronic properties of ladder oligomers of poly(m-aniline) that may be considered as derivatives of azaacenes with cross-conjugated {pi}-systems. Syntheses of ladder oligo(m-aniline)s with 9 and 13 collinearly fused six-membered rings employed Pd-catalyzed aminations and Friedel-Crafts-based ring closures. Structures were confirmed by either X-ray crystallography or correlations between DFT-computed and experimental spectroscopic data such as {sup 1}H, {sup 13}C, and {sup 15}N NMR chemical shifts and electronic absorption spectra. All compounds have planar 'azaacene' moieties. The experimental band gaps E{sub g} {approx} 3.5-3.65 eV, determined by the UV-vis absorption onsets, were in agreement with the TD-DFT-computed vertical excitation energies to the S{sub 1} state. Fluorescence quantum yields of up to 20% were found. Electrochemically estimated HOMO energies of -4.8 eV suggested propensity for a facile one-electron oxidation and just sufficient environmental stability toward oxygen (O{sub 2}). For two oligomers with 'tetraazanonacene' moieties, potentials of E{sup 4+/3+} {approx} 1.6-1.7 V vs SCE were determined for four-electron oxidation to the corresponding tetraradical tetracations.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- National Science Foundation (NSF)
- OSTI ID:
- 1038272
- Journal Information:
- Journal of Organic Chemistry, Vol. 77, Issue 5; ISSN 0022-3263
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Localized triplet excitations and the effect of photo-oxidation in ladder-type poly(p-phenylene) and oligo(p-phenylene)
Two-step mechanism for the photoinduced intramolecular electron transfer in oligo(p-phenylene vinylene)-fullerene dyads