Azadioxatriangulenium and Diazaoxatriangulenium: Quantum Yields and Fundamental Photophysical Properties

Abstract

Over the last decade, we have investigated and exploited the photophysical properties of triangulenium dyes. Azadioxatriangulenium (ADOTA) and diazaoxatriangulenium (DAOTA), in particular, have features that make them useful in various fluorescence-based technologies (e.g., bioimaging). Through our work with ADOTA and DAOTA, we became aware that the reported fluorescence quantum yields (phi(fl)) for these dyes are lower than their actual values. We thus set out to further investigate the fundamental structure-property relationships in these unique conjugated cationic systems. The nonradiative processes in the systems were explored using transient absorption spectroscopy and time-resolved emission spectroscopy in combination with computational chemistry. The influence of molecular oxygen on the fluorescence properties was explored, and the singlet oxygen sensitization efficiencies of ADOTA and DAOTA were determined. We conclude that, for these dyes, the amount of nonradiative deactivation of the first excited singlet state (S-1) of the azaoxa-triangulenium fluorophores is low, that the rate of such deactivation is slower than what is observed in common cationic dyes, that there are no observable radiative transitions occurring from the first excited triplet state (T-1) of these dyes, and that the efficiency of sensitized singlet oxygen production is low (phi(Delta) <= 10%). These photophysical results provide a solid base upon which technological applications of these fluorescent dyes can be built

Fluorescence pH Probes Based on Photoinduced Electron Transfer Quenching of Long Fluorescence Lifetime Triangulenium Dyes

“…First, the results concerning the ADOTA derivatives will be discussed. The absorption and emission spectra of 3 a – 3 cPF 6 measured at pH 2 (Figure A and Table ) are comparable to those measured for similar ADOTA derivatives and the methyl reference compound 3 d ,. The integrated fluorescence intensities (I f ) converge towards zero, as the pH values approaches the basic pH region (Figure A).…”

“…As previously reported the nature of the groups bound to the nitrogen bridges in ADOTA and DAOTA has negligible effects on their absorption and emission spectra . This is also found to be the case for the phenol substituted derivatives where shifts of less than 3 nm are observed when comparing to simple methyl derivatives of ADOTA ( 3 d ) and DAOTA ( 5 d ) shown in Figure . Spectral data are compiled in Table .…”

Design, synthesis, and time-gated cell imaging of carbon-bridged triangulenium dyes with long fluorescence lifetime and red emission

“…We have recently shown that the aza/oxa-triangulenium dyes; ADOTA + and DAOTA + ( Chart 1 ) have remarkable low rates of non-radiative deactivation and low susceptibility to quenching by oxygen, 31 which explains how these organic dyes with fluorescence peaks in the 550 nm–600 nm range, can display unusually long fluorescence lifetimes, close to 20 ns, and high quantum yields ( Φ f ≈ 0.7–0.8).…”

“… 44 – 51 While DMQA + displays long fluorescence lifetime in non-polar solvents it display faster non-radiative deactivation than the planer aza/oxa-triangulenium dyes and is practically non-fluorescent in aqueous solutions. 31 , 42 …”

A Short and Efficient Synthesis of the [3]Triangulene Ring System

“…[17,18] There is agrowing literature predicting the chemistry of 2 [19][20][21][22] and avariety of heterocyclic versions are known. [23][24][25][26][27][28][29][30] In spite of much effort in this field, the parent substance 2,c ommonly known as triangulene or Clarsh ydrocarbon, was only recently prepared and observed as single molecules by scanning probe microscopy. [31] Similar experiments describing the molecularscale preparation of higher homologues 3 and 4 by surfaceassisted dehydrogenation of suitable precursors have been reported very recently.…”