Incorporating BODIPY fluorophores into tetrakis(arylethynyl)benzenes

Six structural isomers of a tetrakis(arylethynyl)benzene (TAEB) chromophore functionalized with dibutylamine and BODIPY moieties as the corresponding donor and acceptor units were prepared. To evaluate the effectiveness of the donor group, two TAEB molecules and three structurally related bis(arylethynyl)benzene (BAEB) isomers containing only acceptors were also synthesized. The electronic absorption and emission spectra of each series were examined. Additionally, computational studies were employed to corroborate the relative energy levels and gaps present in each series.     

Water-soluble red-emitting distyryl-borondipyrromethene (BODIPY) dyes for biolabeling

A series of water-soluble red-emitting distyryl-borondipyrromethene (BODIPY) dyes were designed and synthesized by using three complementary approaches aimed at introducing water-solubilizing groups on opposite faces of the fluorescent core to reduce or completely suppress self-aggregation. An additional carboxylic acid functional group was introduced at the pseudo-meso position of the BODIPY scaffold for conjugation to amine-containing biomolecules/biopolymers. The optical properties of these dyes were evaluated under simulated physiological conditions (i.e., phosphate-buffered saline (PBS), pH 7.5) or in pure water. The emission wavelength (λ(max)) of these labels was found in the 640-660 nm range with quantum yields from modest to unprecedentedly high values (4 to 38%). The bioconjugation of these distyryl-BODIPY dyes with bovine serum albumin (BSA) and the monoclonal antibody (mAb) 12A5 was successfully performed under mild aqueous conditions.     

Regioselective stepwise bromination of boron dipyrromethene (BODIPY) dyes

Halogenated BODIPYs are important synthetic precursors and potential sensitizers for photodynamic therapy (PDT). Electrophilic bromination of pyrrolic-unsubstituted BODIPYs using bromine regioselectively generated mono- to heptabromoBODIPYs in a stepwise fashion in good to excellent yields. These resultant bromoBODIPYs were applied for regioselective substitution and Suzuki coupling reaction to generate BODIPYs 4, 5, 6, and 7 in good to excellent yields. According to NMR and X-ray analysis results, the stepwise bromination first takes place at 2,6-, then at 3,5-, and eventually at 1,7-positions, whereas the regioselective substitution occurs first at 3,5- then at 1,7-positions of the chromophore. The spectroscopic properties of these resultant BODIPYs were studied, which shows the potential application of these bromoBODIPYs as sensitizers for PDT.     

1,7-Disubstituted boron dipyrromethene (BODIPY) dyes: synthesis and spectroscopic properties

1,7-Dihalogenated boron dipyrromethene dyes were successfully synthesized and substituted, thus providing an entry to the final, elusive reactivity pattern. The spectroscopic properties of 1,7-disubstituted BODIPY dyes were studied and are discussed as a function of their structure.     

A new synthesis of symmetric boraindacene (BODIPY) dyes

BODIPY dyes were synthesized from pyrrole-2-carbaldehyde derivatives in high yields; this constitutes a new approach to this dye framework.     

Convenient synthesis of water-soluble nitrilotriacetic acid (NTA) BODIPY dyes

Mono- and bis-NTA-BODIPY dyes have been efficiently synthesized by amide bond formation between hepta-alkylated meso-aryl-BODIPY derivatives and the free amine of mono- and bis-NTA binder surrogates. These new fluorescent hybrids exhibited valuable photophysical properties under buffered aqueous conditions, thus expanding the arsenal of water-soluble BODIPY dyes for potential labeling and monitoring of biological systems and processes.     

Synthesis of paramagnetic BODIPY dyes as new double (spin and fluorescence) sensors

Paramagnetic pyrroline and 1,2,3,6-tetrahydropyridine derivatives of BODIPY and their diamagnetic analogs have been synthesized and characterized as novel redox double sensor and cation sensitive reagents.     

Rational design of boron dipyrromethene (BODIPY)-based photobleaching-resistant fluorophores applicable to a protein dynamics study

We studied the photobleaching of a library of boron dipyrromethene (BODIPY) derivatives with a range of electron densities, and found that the photobleaching rate is influenced by the electron-withdrawing capacity of the substituents. Electron-deficient BODIPYs generated less singlet oxygen, were less reactive to singlet oxygen, and were highly resistant to photobleaching. We confirmed the utility of one of these fluorophores, 2,6-diCO(2)R-BDP, for visualizing EGF receptor dynamics in cells expressing an SNAP-tagged EGF receptor.     

Pyrromethene dyes (BODIPY) can form ground state homo and hetero dimers: photophysics and spectral properties

Homo and hetero dimerisation of two spectroscopically different BODIPY chromophores was studied, namely, 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene and its 5-styryl-derivative. These exhibit very similar absorption and fluorescence spectral shape, but are mutually shifted by ca. 70 nm. For this reason the former and the latter are referred to as the green and red BODIPY, which here are denoted gB and rB, respectively. Various spectroscopic properties of the rB in different common solvents were determined. The calculated and experimental fluorescence quantum yield is found to be close to 100%, the fluorescence relaxation has a single exponential decay with a lifetime of about 4.5 ns, and the F?rster radius for donor-donor energy migration is 67+/-1A. The dimerisation in different solvents was examined by using custom synthesised; mono and bis BODIPY-labelled forms of 1,2-cis-diaminocyclohexane. It is shown that gB and rB can form ground state homo- as well as hetero dimers. The dimers are non-fluorescent, compatible with H-dimers and may act as excitation traps or as acceptors to the corresponding excited monomers.     

Synthesis, fluorescence and two-photon absorption properties of multichromophoric boron-dipyrromethene fluorophores for two-photon-excited fluorescence applications

The synthesis and the characterization of new multichromophoric boron-dipyrromethene dyes are described. Their absorption, photoluminescence as well as their two-photon absorption properties have been investigated. This work shows that assembling several dyes in conjugated multichromophoric structures is a promising strategy for improving the two-photon absorption properties of such fluorophores in the NIR region while retaining their excellent photoluminescence properties.     

Proton- and redox-controlled switching of photo- and electrochemiluminescence in thiophenyl-substituted boron-dipyrromethene dyes

A luminescent molecular switch in which the active thiol/disulfide switching element is attached to a meso-phenyl-substituted boron-dipyrromethene (BDP) chromophore as the signalling unit is presented. The combination of these two functional units offers great versatility for multimodal switching of luminescence: 1) deprotonation/protonation of the thiol/thiolate moiety allows the highly fluorescent meso-p-thiophenol-BDP and its nonfluorescent thiolate analogue to be chemically and reversibly interconverted, 2) electrochemical oxidation of the monomeric dyes yields the fluorescent disulfide-bridged bichromophoric dimer, also in a fully reversible process, and 3) besides conventional photoexcitation, the well separated redox potentials of the BDP also allow the excited BDP state to be generated electrochemically (i.e., processes 1) and 2) can be employed to control both photo- and electrochemiluminescence (ECL) of the BDP). The paper introduces and characterizes the various states of the switch and discusses the underlying mechanisms. Investigation of the ortho analogue of the dimer provided insight into potential chromophore-chromophore interactions in such bichromophoric architectures in both the ground and the excited state. Comparison of the optical and redox properties of the two disulfide dimers further revealed structural requirements both for redox switches and for ECL-active molecular ensembles. By employing thiol/disulfide switching chemistry and BDP luminescence features, it was possible to create a prototype molecular ensemble that shows both fully reversible proton- and redox-gated electrochemiluminescence.     

The electronic structure of the bases of cyanine dyes and the barriers of their conformational transformations

The equilibrium geometry and electronic transitions of cyanine dyes and their bases and also the barriers to rotation of the terminal groups in the ground and excited states were calculated in the AM1 approximation. It was found that in contrast to the cyanine dyes the bases are closer in electronic structure to conjugated systems of the polyene type. The calculated barriers to rotation are significantly higher in the bases than in the dyes. Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya ul., Kiev 253094, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 4, pp. 222–226, July–August, 1999.     

Incorporation of pyrimidine fluorophores into poly(methylmethacrylate) polymer structures

Three polymethyl methacrylate based copolymers bearing arylvinylpyrimidine chromophores have been synthesized in four steps. Spectral properties of the copolymers have been studied in solution, powder and thin films and compared with the corresponding free chromophores. The copolymers exhibit strong emission solvatochromism and act as polarity sensors. They also exhibit halochromism: when adding acid, a bathochromic shift is observed in absorption whereas a red-shifted fluorescence is observed with increased intensity for the methoxy-substituted macromolecule.     

Dihydronaphthalene‐Fused Boron–Dipyrromethene (BODIPY) Dyes: Insight into the Electronic and Conformational Tuning Modes of BODIPY Fluorophores

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 pK_a 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.     

Design of BODIPY dyes as triplet photosensitizers: electronic properties tailored for solar energy conversion,photoredox catalysis and photodynamic therapy

BODIPYs are renowned fluorescent dyes with strong and tunable absorption in the visible region, high thermal and photo-stability and exceptional fluorescence quantum yields. Transition metal complexes are the most commonly used triplet photosensitisers, but, recently, the use of organic dyes has emerged as a viable and more sustainable alternative. By proper design, BODIPY dyes have been turned from highly fluorescent labels into efficient triplet photosensitizers with strong absorption in the visible region (from green to orange). In this perspective, we report three design strategies: (i) halogenation of the dye skeleton, (ii) donor–acceptor dyads and (iii) BODIPY dimers. We compare pros and cons of these approaches in terms of optical and electrochemical properties and synthetic viability. The potential applications of these systems span from energy conversion to medicine and key examples are presented.

BODIPYs offer a versatile platform to build organic triplet photosensitisers for PDT, TTA upconversion and photocatalysis. Tuning their properties provides the opportunity of replacing heavy-metal complexes and can lead to improved sustainability.     

Conformationally restricted dipyrromethene boron difluoride (BODIPY) dyes: highly fluorescent, multicolored probes for cellular imaging

Novel fluorescent, conformationally restricted dipyrromethene boron difluoride (BODIPY) dyes have been prepared by introducing a naphthalenyl group at the meso position of the BODIPY core. These BODIPY dyes exhibit increased fluorescence quantum yields compared with dyes that have a meso-position phenyl group with internal rotation. The absorption and emission wavelengths of such conformationally restricted BODIPY dyes can be easily tuned to the near-IR range by derivatization through a condensation reaction with benzaldehyde derivatives. The two-photon absorption properties of these BODIPY dyes were also investigated and the results show that they exhibit increased two-photon excited fluorescence compared to analogue dyes that contain a phenyl group. The one- and two-photon fluorescence imaging of living cells by using selected BODIPY dyes has been successfully demonstrated.     

Exploiting the versatile assembly of arylpyridine fluorophores for wavelength tuning and SAR

[reaction: see text] The facile modular assembly of polyarylpyridine fluorophores provides two important advantages in the development of fluorescent chemosensors: it allows rapid dissection of the structural requirements for fluorescent chemosensing and it allows dramatic tuning of emission wavelength by changes in a substituent remote from the binding site.