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).
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B. W. Laursen, F. C. Krebs, M. F. Nielsen, K. Bechgaard, J. B. Christensen, N. Harrit 2,6,10-Tris(dialkylamino)-triangulenium Ions. Synthesis, Structure, and Properties of Exceptionally Stable Carbenium Ions J. Am. Chem. Soc. 1998 120 12255
D. F. Duxbury The Photochemistry and Photophysics of Triphenylmethane Dyes in Solid and Liquid Media Chem. Rev. 1993 93 381
M. Vogel, W. Rettig Efficient Intramolecular Fluorescence Quenching in Triphenylmethane-Dyes Involving Excited States With Charge Separation and Twisted Conformations Ber. Bunsen-Ges. Phys. Chem. 1985 89 962
K. H. Drexhage, Structure and Properties of Laser Dyes, in Dye Lasers, ed. F. P. Schäfer, Springer-Verlag, Berlin, 1990, p. 179
R. P. Haugland, Handbook of Fluorescent Probes and Research Products, Molecular Probes, Eugene, 9th edn., 2002
T. Karstens, K. Kobs Rhodamine B and Rhodamine 101 as Reference Substances for Fluorescence Quantum Yield Measurements J. Phys. Chem. 1980 84 1871
U. Brackmann, Lambdachrome Laser-grade Dyes, Lambda-Physik, Göttingen, 1982
K. Drexhage, Fluorescence Efficiency of Laser Dyes, in Standardisation in Spectrophotometry and Luminescence Measurements, Natl. Bur. Stand. Spec. Publ., No. 466, ed. K. D. Mielen, R. A. Velapoldi and R. Mavrodineanu, Government Printing Office, Washington, DC, 1977
K. H. Drexhage, Structure and Properties of Laser Dyes, in Dye Lasers, ed. F. P. Schäfer, in Topics in Applied Physics Springer-Verlag, Berlin, 1973, vol. 1, p. 144
J. C. Martin, R. G. Smith Factors Influencing the Basicities of Triarylcarbinols. The Synthesis of Sesquixanthydrol J. Am. Chem. Soc. 1964 86 2252
J. Reynisson, R. Wilbrandt, V. Brinck, B. W. Laursen, K. Norgaard, N. Harrit, A. M. Brouwer Photophysics of Trioxatriangulenium Ion. Electrophilic Reactivity in the Ground State and Excited Singlet State Photochem. Photobiol. Sci. 2002 1 763
M. Lofthagen, R. VernonClark, K. K. Baldridge, J. S. Siegel Synthesis of Trioxatricornan and Derivatives. Useful Keystones for the Construction of Rigid Molecular Cavities J. Org. Chem. 1992 57 61
J. Reynisson, G. B. Schuster, S. B. Howerton, L. D. Williams, R. N. Barnett, C. L. Cleveland, U. Landman, N. Harrit, J. B. Chaires Intercalation of Trioxatriangulenium Ion in DNA: Binding, Electron Transfer, X-Ray Crystallography, and Electronic Structure J. Am. Chem. Soc. 2003 125 2072
A. Pothukuchy, C. L. Mazzitelli, M. L. Rodriguez, B. Tuesuwan, M. Salazar, J. S. Brodbelt, S. M. Kerwin Duplex and Quadruplex DNA Binding and Photocleavage by Trioxatriangulenium Ion Biochemistry 2005 44 2163
C. C. Barker, M. H. Bride, A. Stamp Steric Effects in Di- and Tri-Arylmethanes. Part I. Electronic Absorption Spectra of o-Methyl Derivatives of Michlers’s Hydrol Blue and Crystal Violet. Conformational Isomers of Crystal Violet J. Chem. Soc. 1959 3957
J. Griffiths, Colour and Constitution of Organic Molecules, Academic Press, London, 1976, p. 96
G. N. Lewis, T. M. Magel, D. Lipkin Isomers of Crystal Violet Ion. Their Absorption and Re-Emission of Light J. Am. Chem. Soc. 1942 64 1774
H. B. Lueck, J. L. McHale, W. D. Edwards Symmetry-Breaking Solvent Effects on the Electronic Structure and Spectra of a Series of Triphenylmethane Dyes J. Am. Chem. Soc. 1992 114 2341
F. C. Adam, W. T. Simpson Electronic Spectrum of 4,4’-bis-Dimethylamino Fuchsone and Related Triphenylmethane Dyes J. Mol. Spec. 1959 3 363
J. Korppi-Tommola, R. W. Yip Solvent Effects on the Visible Absorption Spectrum of Crystal Violet Can. J. Chem. 1981 59 191
C. S. Oliveira, K. P. Branco, M. S. Baptista, G. L. Indig Solvent and Concentration Effects on the Visible Spectra of Tri-para-Dialkylamino-Substituted Triarylmethane Dyes in Liquid Solutions Spectrochim. Acta, Part A 2002 58A 2971
F. Feichtmayr, J. Schlag Influence of solvent and concentration on the spectra of triphenylmethane dyes Ber. Bunsen-Ges. Phys. Chem. 1964 68 95
J. E. Selwyn, J. I. Steinfeld Aggregation of Equilibriums of Xanthene Dyes J. Phys. Chem. 1972 76 762
A. I. Vogel Physical Properties and Chemical Constitution. Part XII. Ethers and Acetals. J. Chem. Soc. 1948 616
H. L. Tavernier, M. M. Kalashnikov, M. D. Fayer Photoinduced Intermolecular Electron Transfer in Complex Liquids: Experiment and Theory J. Chem. Phys. 2000 113 10191
M. Kasha, H. R. Rawls, M. A. El-Bauoumi The Exciton Model in Molecular Spectroscopy Pure Appl. Chem. 1965 11 371
In a double-exponential decay, the terms αiδi are proportional to the area under the decay curve for each decay and therefore to the fractional steady-state intensities of each component. The ratio between absorbed number of photons in a mixture of chromophores is given by the ratio between the absorbances (A = εcl) of each component. Using index M for monomer and D for dimer (Φ is the fluorescence quantum yield), one gets: αMδM/αDδD = (εMcMl/εDcDl) × (ΦM/ΦD) At the total monomer concentration [(Dec2N)3TOTA+PF6−] = 7 × 10−6 M, αM = 0.10, δM = 2.6 ns, αD = 0.90, and δD = 26.4 ns (Table 1). As approximation, the overall quantum yields in heptane, ΦD = 0.10, and benzene, ΦM = 0.40, are used. The nitrogen line at 407 nm was used for excitation (see supplementary information†). This wavelength is at the short-wavelength tail of the absorption spectra of the ion-pair and the dimerised ion-pair (Fig. 3), and the absorption coefficients are difficult to estimate exactly. Roughly, they are the same, based on monomer concentration. Therefore, εM/εD ˜ 0.5. When these values are used, a ratio cM/cD ˜ 5.5 × 10−3 is obtained, corresponding to an association constant K = cD/cM2 ˜ 1010 M−1 for the equilibrium 2 M ? D, at this concentration in heptane. The uncertainty of this estimate must be stressed.
C. A. Hunterand, J. K. M. Sanders The nature of π–π interactions J. Am. Chem. Soc. 1990 112 5525
S. Lovell, B. J. Marquardt, B. Kahr Crystal Violet’s Shoulder J. Chem. Soc., Perkin Trans. 2 1999 2241
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Electronic supplementary information (ESI) available: Experimental details, Figs. S1–S5 and Tables S1–S6. See http://dx.doi.org/10.1039/b501584g
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Laursen, B.W., Reynisson, J., Mikkelsen, K.V. et al. 2,6,10-Tris(dialkylamino)trioxatriangulenium salts: a new promising fluorophore. Ion-pair formation and aggregation in non-polar solvents. Photochem Photobiol Sci 4, 568–576 (2005). https://doi.org/10.1039/b501584g
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DOI: https://doi.org/10.1039/b501584g