2,6,10-Tris(dialkylamino)trioxatriangulenium salts: a new promising fluorophore. Ion-pair formation and aggregation in non-polar solvents

Abstract

The D3h symmetric tris(dialkylamino)trioxatriangulenium ((R2N)3TOTA+) ions are structurally related to classical stains and fluorophores such as triphenylmethane dyes and rhodamines. New derivatives of (R2N)3TOTA+, in which long flexible alkyl chains surround the planar and rigid aromatic core, have been synthesized and isolated as hexafluorophosphate salts. In contrast to short-chain derivatives of triphenylmethane dyes, the new compounds described here are soluble in hydrocarbon solvents. The photophysical properties of these carbenium salts are investigated. Characteristic alterations of the photophysical properties as a function of solvent polarity, concentration and temperature are observed. A model to rationalize the phenomena is presented comprising three states of aggregation, i.e. freely solvated ions, tight ion-pairs, and dimers of ion-pairs. Reduced symmetry in the tight ion-pairs is held responsible for the observed splitting of the long wavelength absorption band. Exciton coupling in the ion-pair dimers leads to reduced oscillator strength of the S0-S1 transition. The model is supported by semi-empirical calculations of the structures and electronic transitions of the free cation and its ion-pair(s).

Ion-Pair Oligomerization of Chromogenic Triangulenium Cations with Cyanostar-Modified Anions That Controls Emission in Hierarchical Materials

“…58 In the preparation of the TOTA + samples in this and all other solution phase experiments, the solubility limit of TOTA + had to be taken into consideration. All concentrated stock solutions were filtered to remove undissolved material, and their concentrations were subsequently standardized.…”

Polarization and Symmetry of Electronic Transitions in Long Fluorescence Lifetime Triangulenium Dyes

“…12 More recently TOTA + has been synthesized with peripheral aminogroups leading to high brightness fluorophores, which can be considered a blueshifted rhodamine-analogue. 13 The same synthetic approach was used to functionalize azadioxatriangulenium (ADOTA + ) with peripheral amino groups, yielding a fluorophore that is even further blueshifted, making it one of the only high brightness fluorophores with emission at shorter wavelengths than fluorescein. 14 High emission yield chromophores based on the TATA + motif were recently prepared by introducing steric constraints in the system.…”

“…13b, 13c, 17 They have high oscillator strengths (ε ≈ 80,000-130,000 M −1 cm −1 ) and quantum yields (Φ ≈ 0.7), lifetimes in the 3-5 ns range, and feature very narrow bands in both absorption and emission.…”

Enhanced fluorescence emission of Me-ADOTA+ by self-assembled silver nanoparticles on a gold film

“…The triangulenes are highly fluorescent, electron rich cationic dyes, capable of photo electron transfer to most donors and they are excellent DNA intercalators [19,23,24]. Peripheral substitution of hydrogen with nitrogen leads to a different class of triangulenium dyes; amino-trioxatriangulene(A-TOTA + ) and amino-azadioxatriangulene(A-ADOTA + ) which effectively are blueshifted symmetric versions of rhodamine and aminoacridine respectively [25,26,27]. …”