Filtern
Dokumenttyp
- Zeitschriftenartikel (13)
- Posterpräsentation (1)
Schlagworte
- Fluorescence (6)
- Charge transfer (3)
- Dyes/pigments (3)
- Fluoreszenz (3)
- Porphyrinoids (3)
- BODIPY (2)
- BODIPY dyes (2)
- Farbstoffe (2)
- NIR-Farbstoffe (2)
- Photophysics (2)
- Protonation (2)
- Absorption (1)
- Aggregates (1)
- Autophagy (1)
- BODIPY-Farbstoffe (1)
- Boron (1)
- Charge (1)
- Chemosensoren (1)
- Circular dichroism (1)
- Density functional calculations (1)
- Electron transfer (1)
- Excimers (1)
- Fluorescent indicators (1)
- Fluorescent probes (1)
- Ladungstransfer (1)
- Lysosome (1)
- MCD spectroscopy (1)
- Mercury (1)
- NIR dyes (1)
- NIR-Bereich (1)
- NMR-Spektroskopie (1)
- Near-infrared fluorophores (1)
- Photophysik (1)
- Porphyrinoide (1)
- Quecksilber (1)
- Real-time imaging (1)
- Ring expansion (1)
- Ring fusion (1)
- Ring-fusion (1)
- Röntgenstrukturanalyse (1)
- Sensoren (1)
- Sensors (1)
- Synthese (1)
- Transfer (1)
Organisationseinheit der BAM
A new class of boron-dipyrromethene (BDP or BODIPY) dyes was obtained by phenanthrene fusion to the β-pyrrole positions, absorbing in the wavelength range of important laser sources. Despite a 'propeller-like' distorted structure in the crystalline state, the chromophore absorbs (log ε ≥ 5) and fluoresces (Φf ≥ 0.8) strongly and can be easily turned into a fluorescence light-up probe. Incorporation into latex beads produces bright and photostable single-dye and Förster Resonance Energy Transfer (FRET) particles for microscopy applications.
Real-time monitoring of newly acidified organelles during autophagy in living cells is highly desirable for a better understanding of intracellular degradative processes. Herein, we describe a reaction-based boron dipyrromethene (BODIPY) dye containing strongly electron-withdrawing diethyl 2-cyanoacrylate groups at the α-positions. The probe exhibits intense red fluorescence in acidic organelles or the acidified cytosol while negligible fluorescence in other regions of the cell. The underlying mechanism is a nucleophilic reaction at the central meso-carbon of the indacene core, resulting in the loss of π-conjugation entailed by dramatic spectroscopic changes of more than 200 nm between its colorless, non-fluorescent leuco-BODIPY form and its red and brightly emitting form. The reversible transformation between red fluorescent BODIPY and leuco-BODIPY along with negligible cytotoxicity qualifies such dyes for rapid and direct intracellular lysosome imaging and cytosolic acidosis detection simultaneously without any washing step, enabling the real-time monitoring of newly acidified organelles during autophagy.
A new series of boron-dipyrromethene (BDP, BODIPY) dyes with dihydronaphthalene units fused to the β-pyrrole positions (1 a-d, 2) has been synthesised and spectroscopically investigated. All the dyes, except pH-responsive 1 d in polar solvents, display intense emission between 550-700 nm. Compounds 1 a and 1 b with a hydrogen atom and a methyl group in the meso position of the BODIPY core show spectroscopic properties that are similar to those of rhodamine 101, thus rendering them potent alternatives to the positively charged rhodamine dyes as stains and labels for less polar environments or for the dyeing of latex beads. Compound 1 d, which carries an electron-donating 4-(dimethylamino)phenyl group in the meso position, shows dual fluorescence in solvents more polar than dibutyl ether and can act as a pH-responsive "light-up" probe for acidic pH. Correlation of the pKa data of 1 d and several other meso-(4-dimethylanilino)-substituted BODIPY derivatives allowed us to draw conclusions on the influence of steric crowding at the meso position on the acidity of the aniline nitrogen atom. Preparation and investigation of 2, which carries a nitrogen instead of a carbon as the meso-bridgehead atom, suggests that the rules of colour tuning of BODIPYs as established so far have to be reassessed; for all the reported couples of meso-C- and meso-N-substituted BODIPYs, the exchange leads to pronounced redshifts of the spectra and reduced fluorescence quantum yields. For 2, when compared with 1 a, the opposite is found: negligible spectral shifts and enhanced fluorescence. Additional X-ray crystallographic analysis of 1 a and quantum chemical modelling of the title and related compounds employing density functional theory granted further insight into the features of such sterically crowded chromophores.
The successful synthesis of tetraphenyltetraphenanthroporphyrin (TPTPhenP; 5a) in 2006 under modified Rothemund–Lindsey conditions yielded a tetraphenyl porphyrinoid with a B band redshifted to an unprecedented 576 nm. Radially symmetric fused-ring expansion of tetraphenylporphyrin with phenanthrene moieties results in very deep saddling due to steric crowding and very marked redshifts of the Q and B (or Soret) porphyrinoid absorption bands. The extent to which the TPTPhenP structure can be further modified is explored, and the optical properties of TPTPhenPs are analyzed based on a perimeter model approach that makes use of time-dependent DFT calculations and magnetic circular dichroism spectroscopy and also based on a detailed analysis of the fluorescence emission. Attempts to introduce substituents at the ortho and meta positions of the meso-phenyl groups and to insert a central metal proved unsuccessful. The synthesis of a series of TPTPhenPs with strong electron-withdrawing (—CN, —NO2) and -donating (—CH3, —N(CH3)2) substituents at the para positions of the meso-phenyl rings is reported. Marked redshifts of the main spectral bands were consistently observed. The most pronounced spectral changes were observed with —N(CH3)2 groups (5i) due to a marked destabilization of the HOMO, which has large MO coefficients on the meso-carbon atoms. Protonation of 5i at both the ligand core and at the —N(CH3)2 groups resulted in unprecedented Q00 band absorption at wavelengths greater than 1200 nm.
The synthesis of a series of novel core-modified and fused-ring-expanded tetraphenylporphyrins is reported. Theoretical calculations and magnetic circular dichroism (MCD) and fluorescence spectroscopic measurements were used to analyze the effect of core modification with Group 16 oxygen, sulfur, selenium, and tellurium atoms on the optical properties and electronic structures of the porphyrins. Marked redshifts of the Q and B bands and accelerated intersystem-crossing rates were observed, thus making these compounds potentially suitable for use in a variety of applications. The scope for further fine-tuning of these optical properties based on additional structural modifications, such as the incorporation of fused benzene rings to form ABAB structures by using a thiophene precursor with a fused bicyclo[2.2.2]octadiene ring and the introduction of various substituents onto the meso-phenyl rings, is also examined.
The X-ray crystallographic, optical spectroscopic, and electrochemical properties of a newly synthesized class of boron-diindomethene (BDI) dyes and their tetrahydrobicyclo precursors (bc-BDP) are presented. The BDI chromophore was designed to show intensive absorption and strong fluorescence in an applicationary advantageous spectral range. Its modular architecture permits fusion of a second subunit, for example, a receptor moiety to the dye's core to yield directly linked yet perpendicularly prearranged composite systems. The synthesis was developed to allow facile tuning of the chromophore platform and to thus adjust its redox properties. X-ray analysis revealed a pronounced planarity of the chromophore in the case of the BDIs, which led to a remarkable close packing in the crystal of the simplest derivative. On the other hand, deviation from planarity was found for the diester-substituted bc-BDP benzocrown that exhibits a butterfly-like conformation in the crystal. Both families of dyes show charge- or electron-transfer-type fluorescence-quenching characteristics in polar solvents when equipped with a strong donor in the meso-position of the core. These processes can be utilized for signaling purposes if an appropriate receptor is introduced. Further modification of the chromophore can invoke such a guest-responsive intramolecular quenching process, also for receptor groups of low electron density, for example, benzocrowns. In addition to the design of various prototype molecules, a promising fluoroionophore for Na+ was obtained that absorbs and emits in the 650 nm region and shows a strong fluorescence enhancement upon analyte binding. Furthermore, investigation of the remarkable solvatokinetic fluorescence properties of the butterfly-like bc-BDP derivatives suggested that a second intrinsic nonradiative deactivation channel can play a role in the photophysics of boron-dipyrromethene dyes.
Highly emissive phenanthrene-fused boron–dipyrromethene (PBDP) dyes have been spectroscopically characterized in a series of solvents. The influence of different substituents (-H,
-I, -CN, -DMA or a 15C5-crown ether) in the para-position of a phenyl ring attached to the meso-position of the BODIPY core is discussed. This family of dyes has an intense emission at lambda > 630 nm, with fluorescence quantum yields between 0.7 and 1.0 in all solvents studied, except in the case of the dimethylamino-substituted
derivative, PBDP-DMA, which undergoes excited-state intramolecular charge transfer (CT), leading to broadband dual fluorescence in highly polar solvents. Introduction of a weaker electron donor such as a benzocrown to the meso-position is not able to trigger a second (charge or electron transfer) process and, interestingly, heavy atom (iodine, PBDP-I derivative) substitution at that moiety does also not have a relevant influence on the photophysics, i.e., enhanced intersystem crossing was not observed.
Electrochemical studies of PBDP-DMA complement the data reported and stress the fact that the decrease in fluorescence of PBDP-DMA in highly polar solvents is due to an excited-state CT process
rather than to a photoinduced electron transfer (PET).
The tendency of boron-dipyrromethene (BODIPY) dyes to associate in water is well known, and usually a cause for inferior fluorescence properties. Synthetic efforts to chemically improve BODIPYs’ water solubility and minimize this problem have been numerous in the past. However, a deeper understanding of the phenomena responsible for fluorescence quenching is still required. Commonly, the spectroscopic behaviour in aqueous media has been attributed to aggregate or excimer formation, with such works often centring on a single BODIPY family. Herein, we provide an integrating discussion including very diverse types of BODIPY dyes. Our studies revealed that even subtle structural changes can distinctly affect the association behaviour of the fluorophores in water, involving different photophysical processes. The palette of behaviour found ranges from unperturbed emission, to the formation of H or J aggregates and excimers, to the involvement of tightly bound, preformed excimers. These results are a first step to a more generalized understanding of spectroscopic properties vs. structure, facilitating future molecular design of BODIPYs, especially as probes for biological applications.