title: Base-assisted one-pot synthesis of N,N',N"-triaryltriazatriangulenium dyes: enhanced fluorescence efficiency by steric constraints.
abstract: In this paper we report the first synthesis of cationic N,N',N"-triaryltriazatriangulenium dyes (Ar(3)-TATA(+)). Previously, only alkyl-substituted triazatriangulenium derivatives (R(3)-TATA(+)) were known, a consequence of the low reactivity of anilines in the aromatic nucleophilic substitution reaction leading to the formation of the TATA(+) core. The synthesis of Ar(3)-TATA(+) was achieved by heating the tris(2,6-dimethoxyphenyl)methylium ion (DMP(3)C(+)) in various anilines in the presence of NaH. In the solvent-free reaction all three aryl substituents could be introduced despite the low reactivity of the anilines. The symmetric Ar(3)-TATA(+) derivatives with Ar = phenyl (2), 4-methoxyphenyl (3), and 4-bromophenyl (4) were synthesized. Single crystal structures of 2 and 4 were obtained as BF(4)(-) salts, where torsional angles larger than 80° were observed between the TATA(+) chromophore and the aryl substituents. The photophysical properties were studied in solution and in thin films. The results show that the Ar(3)-TATA(+) dyes have a surprising 3-fold increase in fluorescence quantum yields when compared to the parent alkyl-substituted R(3)-TATA(+) salts. With a high quantum yield (>50%) and emission in the red (λ(fl) = 560 nm) the Ar(3)-TATA(+) dyes represent a promising new addition to the family of superstable cationic triangulenium dyes. Additionally, the synthesized tribromo derivative 4 is shown to be a potential triagonal synthon for polymers and other macromolecules.
authors.affiliation: Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK2100 København Ø, Denmark.
authors.forename: Peter
authors.initials: P
authors.lastname: Hammershøj
authors.forename: Thomas Just
authors.initials: TJ
authors.lastname: Sørensen
authors.forename: Bao-Hang
authors.initials: BH
authors.lastname: Han
authors.forename: Bo W
authors.initials: BW
authors.lastname: Laursen
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry; D001372:Aza Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D004396:Coloring Agents / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D005453:Fluorescence; D008958:Models, Molecular; D015394:Molecular Structure
chemical_list: D000814:Aniline Compounds; D001372:Aza Compounds; D004396:Coloring Agents; C023650:aniline