title: Ladder oligo(m-aniline)s: derivatives of azaacenes with cross-conjugated π-systems.
abstract: 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 π-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 (1)H, (13)C, and (15)N NMR chemical shifts and electronic absorption spectra. All compounds have planar "azaacene" moieties. The experimental band gaps E(g) ≈ 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(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(2)). For two oligomers with "tetraazanonacene" moieties, potentials of E(4+/3+) ≈ 1.6-1.7 V vs SCE were determined for four-electron oxidation to the corresponding tetraradical tetracations.
authors.affiliation: Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA. arajca1@unl.edu
authors.forename: Andrzej
authors.initials: A
authors.lastname: Rajca
authors.forename: Przemysław J
authors.initials: PJ
authors.lastname: Boratyński
authors.forename: Arnon
authors.initials: A
authors.lastname: Olankitwanit
authors.forename: Kouichi
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Maren
authors.initials: M
authors.lastname: Pink
authors.forename: Suchada
authors.initials: S
authors.lastname: Rajca
mesh_terms: D000814:Aniline Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D000814:Aniline Compounds; C023650:aniline