2015, Wiktorowski, Simon, Daltrozzo, Ewald, Zumbusch, Andreas

Water-soluble, fluorescence-switchable derivatives of pyrrolopyrrole cyanines (PPCys) which serve as near-infrared pH indicators have been synthesized. The dyes reported have pK_a values of 2.4–3.4 and thus are suitable for sensing in highly acidic environments. The new pH probes were evaluated by fluorescence imaging experiments in a cellular environment

2014, Marks, Timo, Daltrozzo, Ewald, Zumbusch, Andreas

reaction of POCl3-activated, readily soluble diketopyrrolopyrrole (DPP) with 2-aminoheteroaromatics to yield 1:1 and 1:2 hydrogen chelates is described. Complexation of these hydrogen chelates with boron reagents results in thermally and photochemically stable fluorescent dyes (PP–azacyanines). The 1:2 complexes in particular absorb at long wavelengths and are brightly fluorescing. The rich photophysics of the new compounds are presented. Both the pronounced vibrational fine structure of the S0[RIGHTWARDS ARROW]S1 transitions and the observed fluorescence phenomena allow detailed conclusions to be made on the correlation between molecular structure and optical properties

2011-02-07, Fischer, Georg, Daltrozzo, Ewald, Zumbusch, Andreas

Very invisible: Bis(pyrrolopyrrole) cyanines are extended chromophores based on diketopyrrolopyrroles (general structure shown). The compounds are characterized by extremely high extinction coefficients, narrowband absorption in the near-IR range, and strong fluorescence around 1 μm. Since absorption in the visible region is negligible, they approach the ideal of selective NIR absorbers.

2011, Fischer, Georg, Klein, Matthias, Daltrozzo, Ewald, Zumbusch, Andreas

To tune their optical properties, a large variety of pyrrolopyrrole cyanines (PPCys) were synthesized with substitutedheteroaromatics such as quinoline, benzothiazole, and oxazole derivatives as terminal groups. Thus, a broad range of stable, highly fluorescing near-infrared (NIR) dyes with high absorptivities between 690 to 845 nm is accessible. The large number of newly synthesized compounds allows a detailed discussion of the correlation between molecular structure and the optical properties of the first electronic transition.

2015, Opitz, Andreas, Sulger, Werner, Daltrozzo, Ewald, Koch, Rainer

An improved route to 2-substituted 6-hydroxy-[3H]-pyrimidin-4-ones 4 and to 2-substituted 4,6-dichloropyrimidines 5 is reported. Without using highly toxic reactants, compounds 4 can be prepared conveniently in a one pot synthesis on a one mol scale with average yields up to 80 %. 4,6-Dichloropyrimidines 5, which are usually prepared in small quantities, are synthesized with average yields of 80 %, using up to 80 g of starting material. The mechanism of the chlorination of 4 is investigated computationally for the first time. The results suggest that the chlorination with phosphoryl chloride occurs in an alternating phosphorylation–chlorination manner (pathway 1) which is preferred over a sequence which starts with two phosphorylations. The investigated 4,6-dichloropyrimidines described herein form strong complexes with dichlorophosphoric acid but weak complexes with hydrochloric acid (generated during workup). These latter complexes explain the necessity of using aqueous sodium carbonate during the working up. In order to prevent possible formation of pyrimidinium salts between intermediates or the final dichloropyrimidines and unreacted hydroxypyrimidone, the latter could be deactivated with a strong acid such as dichlorophosphoric acid, thus allowing chlorination but prohibiting salt formation. Because of its general applicability to all nitrogen heterocycle chlorinations with phosphoryl chloride, the proposed route to dichloropyrimidines without solvent or side products, using less toxic reactants, is of general synthetic interest.

2012-02-28, Wiktorowski, Simon, Fischer, Georg, Winterhalder, Martin, Daltrozzo, Ewald, Zumbusch, Andreas

A series of novel pyrrolopyrrole cyanines (PPCys) bearing various aminophenyl substituents at the diketopyrrolopyrrole (DPP) core are presented. Compared to their alkoxyphenyl substituted analogues, these dyes feature additional intense electronic transitions of charge-transfer character which give detailed insight into the optical properties of PPCys. The energetic mixing of the involved orbitals has pronounced effects on the absorption and fluorescence behavior. Protonation of the amino function suppresses these effects and leads to a pronounced increase in fluorescence quantum yield. The photophysics of the dyes can be rationalized by means of a simple energy scheme.

2011-01-25, Akers, Walter J., Kim, Chulhong, Berenzin, Mikhail, Guo, Kevin, Fuhrhop, Ralph, Lanza, Gregory M., Fischer, Georg, Daltrozzo, Ewald, Zumbusch, Andreas, Cai, Xin, Wang, Lihong V., Achilefu, Samuel

The contrast mechanisms used for photoacoustic tomography (PAT) and fluorescence imaging differ in subtle, but significant, ways. The design of contrast agents for each or both modalities requires an understanding of the spectral characteristics as well as intra- and intermolecular interactions that occur during formulation. We found that fluorescence quenching that occurs in the formulation of near-infrared (NIR) fluorescent dyes in nanoparticles results in enhanced contrast for PAT. The ability of the new PAT method to utilize strongly absorbing chromophores for signal generation allowed us to convert a highly fluorescent dye into an exceptionally high PA contrast material. Spectroscopic characterization of the developed NIR dye-loaded perfluorocarbon-based nanoparticles for combined fluorescence and PA imaging revealed distinct dye-dependent photophysical behavior. We demonstrate that the enhanced contrast allows detection of regional lymph nodes of rats in vivo with time-domain optical and photoacoustic imaging methods. The results further show that the use of fluorescence lifetime imaging, which is less dependent on fluorescence intensity, provides a strategic approach to bridge the disparate contrast reporting mechanisms of fluorescence and PA imaging methods.

2014, Wiktorowski, Simon, Rosazza, Christelle, Winterhalder, Martin, Daltrozzo, Ewald, Zumbusch, Andreas

Water-soluble derivatives of pyrrolopyrrole cyanines (PPCys) have been synthesized by a post-synthetic modification route. In highly polar media, these dyes are excellent NIR fluorophores. Labeling experiments show how these novel dyes are internalized into mammalian cells.

2012, Wiktorowski, Simon, Fischer, Georg, Daltrozzo, Ewald, Zumbusch, Andreas

Fluorescent dyes are the basis for a broad range of modern techniques in life and material sciences. Consequently, there is a pressing need for the development of new classes of NIR fluorophores in recent years. Pyrrolopyrrole Cyanines (PPCys) are a novel class of NIR chromophores that were first presented in 2007 by Fischer and coworkers.[1] Their optical properties are marked by strong and narrowband NIR absorptions, strong NIR fluorescence and hardly any absorption in the visible range. The absorption maxima can be tuned over a broad range while high fluorescence quantum yields are maintained. PPCys are attractive candidates for labelling applications or as selective NIR absorbers. Moreover, PPCys exhibit very high photostability. Due to these outstanding photophysical properties, PPCys are heading into a promising future as NIR dyes.

2011, Fischer, Georg, Daltrozzo, Ewald, Zumbusch, Andreas

Sehr unsichtbar: Bis(pyrrolopyrrol)-Cyanine sind ausgedehnte Chromophore auf der Basis von Diketopyrrolopyrrolen (siehe allgemeine Struktur). Die Verbindungen zeigen eine sehr hohe, schmalbandige Absorption im Nah-Infrarot(NIR)-Bereich und intensive Fluoreszenz bei 1 μm. Da sie im sichtbaren Bereich fast nicht absorbieren, kommen sie dem Ideal eines selektiven NIR-Absorbers nahe.