Boron Dipyrromethene Dyes Research Articles

Endohedral functionalization of chiral metal-organic cages for encapsulating achiral dyes to induce circularly polarized luminescence

<h2>Summary</h2> Circularly polarized luminescence (CPL) is useful for 3D optical imaging and optical storage, but it remains a big challenge to prepare chiral compounds with both strong emission and high-dissymmetry factor (<i>g</i>_lum). Here, we demonstrate that encapsulation of achiral dyes into hollow cages can inhibit the aggregation-caused quenching (ACQ) behavior and promote CPL induction and amplification. This leads to the synthesis of two chiral hexahedral Pd₆<b>L</b>₁₂ cages with crown ether or methoxymethyl moieties. Complexation of K⁺ with crown ethers allows inclusion of anionic achiral boron-dipyrromethene (BODIPY) dyes into the cage cavities to form stable host-guest complexes by cation-anion and host-guest interactions. Although both the cage and dyes exhibit no CPL, their host-guest complexes display strong CPL emissions with the <i>g</i>_lum factors in the order of 10⁻³ in solution. Upon crystallization, one order of magnitude amplification of the glum values in the cage-dye adducts (up to 2.4 × 10⁻²) is obtained.

Photochemical Properties and Stability of BODIPY Dyes

The present study is devoted to the combined experimental and theoretical description of the photophysical properties and photodegradation of the new boron-dipyrromethene (BODIPY) derivatives obtained recently for biomedical applications, such as bacteria photoinactivation (Piskorz et al., Dyes and Pigments 2020, 178, 108322). Absorption and emission spectra for a wide group of solvents of different properties for the analyzed BODIPY derivatives were investigated in order to verify their suitability for photopharmacological applications. Additionally, the photostability of the analyzed systems were thoroughly determined. The exposition to the UV light was found first to cause the decrease in the most intensive absorption band and the appearance of the hypsochromically shifted band of similar intensity. On the basis of the chromatographic and computational study, this effect was assigned to the detachment of the iodine atoms from the BODIPY core. After longer exposition to UV light, photodegradation occurred, leading to the disappearance of the intensive absorption bands and the emergence of small intensity signals in the strongly blue-shifted range of the spectrum. Since the most intensive bands in original dyes are ascribed to the molecular core bearing the BF2 moiety, this result can be attributed to the significant cleavage of the BF2 ring. In order to fully characterize the obtained molecules, the comprehensive computational chemistry study was performed. The influence of the intermolecular interactions for their absorption in solution was analyzed. The theoretical data entirely support the experimental outcomes.

DFT study of effect of substituents on second-order NLO response of novel BODIPY dyes

Based on molecular structural design of boron-dipyrromethene (BODIPY), nine BODIPY derivatives decorated with vinyl, phenyl, dimethylamino, nitro and aldehyde group substituents, respectively, have been systematically investigated by the density function theory (DFT) method. The purposes of this paper are to study the effect of various substituents and their positions on geometric structures, electronic structures and second-order nonlinear optical (NLO) properties. In addition, the effects of polarizable environment and electric fields on the first hyperpolarizabilities (βtot) values have been investigated. It is found that the incorporation of strong electron-donating dimethylamino could induce a significant enhancement of the βtot values, and the βtot values of the bilateral α-position substitution are much larger with respect to the unilateral α-position substitution, because those substituents are able to expend the BODIPYs’ delocalized π-electron system to different extents. Time-dependent DFT results suggest that the increasement of the βtot values is related to the intramolecular charge transfer from substituents to BODIPY core. Thus, forming a D-π-A model is favorable for increasing the βtot values, where BODIPY was used as electron accepting. Hence, we hope this work will be beneficial to further investigating versatile and novel NLO materials.

BODIPY-attached zinc(II) complexes of curcumin drug for visible light assisted photo-sensitization, cellular imaging and targeted PDT.

Boron-dipyrromethene (BODIPY) based photosensitizers as porphyrinoids and curcumin as natural product possess exciting photophysical features suitable for theranostic applications, namely, imaging and photodynamic therapy (PDT). Limited aqueous solubility and insufficient physiological stability, however, reduce their efficacy significantly. We have designed a novel strategy to deliver these two unusable cytotoxins simultaneously in cancer cells and herein, report the synthesis, characterization and imaging-assisted photocytotoxicity of three zinc(II) complexes containing N3-donor dipicolylamine (dpa) ligands (L1-3) and O,O-donor curcumin (Hcur) viz. [Zn(L1)(cur)]Cl (1), [Zn(L2)(cur)]Cl (2) and [Zn(L3)(cur)]Cl (3), where L2 and L3 have pendant fluorescent BODIPY and non-emissive di-iodo-BODIPY moieties. Metal chelation imparted remarkable biological stability (pH ∼7.4) to the respective ligands and induces significant aqueous solubility. These ternary complexes could act as replacements of the existing metalloporphyrin-based PDT photosensitizers as their visible-light photosensitizing ability is reinforced by the dual presence of blue light absorbing curcumin and green light harvesting BODIPY units. Complex 2 having emissive BODIPY unit L2 and curcumin, showed mitochondria selective localization in HeLa, MCF-7 cancer cells and complex 3, the di-iodinated analogue of complex 2, exhibited type-I/II PDT activity via inducing apoptosis through mitochondrial membrane disruption in cancer cells while being significantly nontoxic in dark and to the healthy cells.

Recent developments of BODIPY-based colorimetric and fluorescent probes for the detection of reactive oxygen/nitrogen species and cancer diagnosis

• A general introduction of BODIPY dyes and their advantageous properties for biological applications are presented. • The concept and sensing mechanisms of fluorescent probes are discussed. • Recent developments and perspectives of BODIPY/aza-BODIPY-based probes for ROS/RNS and cancer are reviewed. Boron-dipyrromethene (BODIPY) platforms have been recognized as potential candidates for a wide range of applications, especially for constructing fluorescent probes due to their unique photophysical properties, outstanding photo- and chemical stabilities, and feasible derivatization. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important chemically reactive species containing oxygen and nitrogen, respectively, which are closely associated with various physiological processes. In addition, some ROS and RNS may cause environmental concerns. Owing to their significant importance in humans, a great number of ROS/RNS fluorescent probes have been designed and widely utilized over the last few years. In particular, the development of smart fluorescent molecules for the early-stage diagnosis of cancer and surveillance of reoccurrence is becoming increasingly important for reducing cancer-related deaths. This review highlighted the design principle and applications of fluorescent probes on the basis of the BODIPY skeleton since 2015, ranging from BODIPY/aza-BODIPY small molecules and macromolecules to delicate nanoparticles for tracking of ROS/RNS and cancer imaging. Finally, their drawbacks, challenges, and perspectives for biomedical applications are also discussed.

Preparation of a Multicarbazole‐Based Nanocapsule Capable of Largely Modulating Guest Spectroscopic Properties in Water

A nanocapsule composed of multiple carbazole panels (ca. 12 panels) was quantitatively generated from bent carbazole-based amphiphiles in water. Unlike previously reported macrocycles and coordination cages bearing several carbazole panels, the resultant nanocapsule displays enhanced emissivity and improved electrochemical stability as compared with the monomeric amphiphile. The spectroscopic properties of substituted coumarin and boron-dipyrromethene dyes can be modulated upon encapsulation by the nanocapsule in water. In the cavity, a highly blue-shifted absorption band is observed from largely twisted coumarin dyes and two absorption bands are found from boron-dipyrromethene dimers stacked in an unusual L-shaped fashion. Moreover, the encapsulated dimers exhibit unique excimer-like emission.

Graphene Quantum Dots Decorated with Boron Dipyrromethene Dye Derivatives for Photodynamic Therapy

Photodynamic therapy (PDT) emerged as a promising cancer therapeutic technique due to the prospect of triggering and controlling the drug action with light, which will reduce the detrimental side e...

Effect of ms-substitution on aggregation behavior and spectroscopic properties of BODIPY dyes in aqueous solution, Langmuir-Schaefer and poly(methyl methacrylate) thin films

It is well known that boron-dipyrromethene (BODIPY) dyes have a remarkable combination of photophysical and photochemical properties, which are significant for practical use. Unfortunately, the application of BODIPYs in optical devices and biosensorics is severely limited due to the aggregation quenching effect (ACQ), the effects of the internal filter and/or the formation of excimers. One way to prevent fluorescence quenching is to synthesize new molecules BODIPY with a highly complicated structural organization or hybrid systems based on them. But in this paper, we demonstrate that the introduction of simple aliphatic or aryl substituents into the ms-position of the BODIPY molecule is an effective way to control the aggregation in various states: thin mono- and multilayer Langmuir-Schaefer (LS) films, polymer films and concentrated solutions, including aqueous ones. The results of experimental studies of the aggregation behavior of BODIPYs (BDP1-BDP3) are in good agreement with the theoretical calculations data of di- and tetramers, as well as multilayer packing. This allows to adjust the spectral properties of luminophores to the most possible types of their real applications in practical areas.

Loading and Release of Charged and Neutral Fluorescent Dyes into and from Mesoporous Materials: A Key Role for Sensing Applications.

The aim of this study is to determine the efficiency of loading and release of several zwitterionic, neutral, anionic and cationic dyes into/from mesoporous nanoparticles to find the optimum loading and release conditions for their application in detection protocols. The loading is carried out for MCM-41 type silica supports suspended in phosphate-buffered saline (PBS) buffer (pH 7.4) or in acetonitrile, involving the dyes (rhodamine B chloride, rhodamine 101 chloride, rhodamine 101 perchlorate, rhodamine 101 inner salt, meso-(4-hydroxyphenyl)-boron–dipyrromethene (BODIPY), sulforhodamine B sodium salt and fluorescein 27). As a general trend, rhodamine-based dyes are loaded with higher efficiency, when compared with BODIPY and fluorescein dyes. Between the rhodamine-based dyes, their charge and the solvent in which the loading process is carried out play important roles for the amount of cargo that can be loaded into the materials. The delivery experiments carried out in PBS buffer at pH 7.4 reveal for all the materials that anionic dyes are more efficiently released compared to their neutral or cationic counterparts. The overall best performance is achieved with the negatively charged sulforhodamine B dye in acetonitrile. This material also shows a high delivery degree in PBS buffer.

The effect of hydrogen bonds on the ultrafast relaxation dynamics of a BODIPY dimer.

The influence of hydrogen bonds (H-bonds) in the structure, dynamics, and functionality of biological and artificial complex systems is the subject of intense investigation. In this broad context, particular attention has recently been focused on the ultrafast H-bond dependent dynamical properties in the electronic excited state because of their potentially dramatic consequences on the mechanism, dynamics, and efficiency of photochemical reactions and photophysical processes of crucial importance for life and technology. Excited-state H-bond dynamics generally occur on ultrafast time scales of hundreds of femtoseconds or less, making the characterization of associated mechanisms particularly challenging with conventional time-resolved techniques. Here, 2D electronic spectroscopy is exploited to shed light on this still largely unexplored dynamic mechanism. An H-bonded molecular dimer prepared by self-assembly of two boron-dipyrromethene dyes has been specifically designed and synthesized for this aim. The obtained results confirm that upon formation of H-bonds and the dimer, a new ultrafast relaxation channel is activated in the ultrafast dynamics, mediated by the vibrational motions of the hydrogen donor and acceptor groups. This relaxation channel also involves, beyond intra-molecular relaxations, an inter-molecular transfer process. This is particularly significant considering the long distance between the centers of mass of the two molecules. These findings suggest that the design of H-bonded structures is a particularly powerful tool to drive the ultrafast dynamics in complex materials.

Click Conjugation of Boron Dipyrromethene (BODIPY) Fluorophores to EGFR-Targeting Linear and Cyclic Peptides.

Through a simple 1,3-cycloaddition reaction, three BODIPY-peptide conjugates that target the extracellular domain of the epidermal growth factor receptor (EGFR) were prepared and their ability for binding to EGFR was investigated. The peptide ligands K(N3)LARLLT and its cyclic analog cyclo(K(N3)larllt, previously shown to have high affinity for binding to the extracellular domain of EGFR, were conjugated to alkynyl-functionalized BODIPY dyes 1 and 2 via a copper-catalyzed click reaction. This reaction produced conjugates 3, 4, and 5 in high yields (70–82%). In vitro studies using human carcinoma HEp2 cells that overexpress EGFR demonstrated high cellular uptake, particularly for the cyclic peptide conjugate 5, and low cytotoxicity in light (~1 J·cm−2) and darkness. Surface plasmon resonance (SPR) results show binding affinity of the three BODIPY-peptide conjugates for EGFR, particularly for 5 bearing the cyclic peptide. Competitive binding studies using three cell lines with different expressions of EGFR show that 5 binds specifically to EGFR-overexpressing colon cancer cells. Among the three conjugates, 5 bearing the cyclic peptide exhibited the highest affinity for binding to the EGFR protein.

Accelerated discovery of boron-dipyrromethene sensitizer for solar cells by integrating data mining and first principle

Boron-dipyrromethene (BODIPY) is one promising class of sensitizers for dye-sensitized solar cells (DSSCs) due to unique merits of high absorption coefficient and versatile structural modification capability. However, such derivatives usually suffer from limited power conversion efficiencies (PCEs) because of narrow light absorption band and low electron injection. To aid the discovery of BODIPY sensitizers, we employ an inverse design method to design efficient sensitizers by integrating data mining and first-principle techniques. We establish robust data-mining models using genetic algorithm and multiple linear regression, where the features are filtered from 5515 descriptors and their meanings are explicitly explored for next inverse designs. Based on the features’ understanding, we design candidates NH1-6 and predict their PCEs, demonstrating remarkable enhancements (58% maximum) compared to previous works. Furthermore, their optoelectronic properties including maximum absorption wavelengths, oscillator strengths, bandgaps, transferred charges, charge transferred distances, TiO2 conduction band shifts, short-circuit currents and electron injection efficiencies simulated via first-principle calculations indicate significant increasements (93 nm, 122.41%, 23.70%, 36.36%, 471.17%, 63.64%, 28.55%, 107.86% maximum), which testifies the corresponding highly predicted PCEs and may overcome BODIPY dyes’ shortcomings. The as-designed BODIPY sensitizers can be promising candidates for DSSCs, and such method could help accelerate the discovery of other energy materials.

Selective Butyrate Esterase Probe for the Rapid Colorimetric and Fluorogenic Identification of Moraxella catarrhalis.

Clinical identification of the pathogenic bacterium Moraxella catarrhalis in cultures relies on the detection of bacterial butyrate esterase (C4-esterase) using a coumarin-based fluorogenic substrate, 4-methylumbelliferyl butyrate. However, this classical probe may give false-positive responses because of its poor stability and lack of specificity. Here, we report a new colorimetric and fluorogenic probe design employing a meso-ester-substituted boron dipyrromethene (BODIPY) dye for the specific detection of C4-esterase activity expressed by M. catarrhalis. This new probe has resistance to nonspecific hydrolysis that is far superior to the classical probe and also selectively responds to esterase with rapid colorimetric and fluorescence signal changes and large "turn-on" ratios. The probe was successfully applied to the specific detection of M. catarrhalis with high sensitivity.

Near-Infrared BODIPY-Acridine Dyads Acting as Heavy-Atom-Free Dual-Functioning Photosensitizers.

Boron dipyrromethene (BODIPY) dyes represent a particular class within the broad array of potential photosensitizers. Their highly fluorescent nature opens the door for theragnostic applications, combining imaging and therapy using a single, easily synthesized chromophore. However, near-infrared absorption is strongly desired for photodynamic therapy to enhance tissue penetration. Furthermore, singlet oxygen should preferentially be generated without the incorporation of heavy atoms, as these often require additional synthetic efforts and/or afford dark cytotoxicity. Solutions for both problems are known, but have never been successfully combined in one simple BODIPY material. Here, we present a series of compact BODIPY-acridine dyads, active in the phototherapeutic window and showing balanced brightness and phototoxic power. Although the donor-acceptor design was envisioned to introduce a charge transfer state to assist in intersystem crossing, quantum-chemical calculations refute this. Further photophysical investigations suggest the presence of exciplex states and their involvement in singlet oxygen formation.

Syntheses of BODIPY-incorporated polymer nanoparticles with strong fluorescence and water compatibility

Borondipyrromethene (BODIPY) dyes have attracted enormous interest due to their excellent photo-physical and chemical properties. However, the strong hydrophobic nature of the dyes limits their applications in water based biological and medical samples. In this work, BODIPY derivatives bearing vinyl group were synthesized and polymerized to obtain high dispersible nanoparticles. The BODIPY monomers were synthesized via esterification of their phenol groups with acryloyl chlorides and fully characterized by NMR, MS, UV–vis, and fluorescence spectroscopies. BODIPY fluorescent polymer nanoparticles were prepared using precipitation polymerization of the BODIPY monomers with methacrylic acid (MAA) in the presence of cross-linkers and characterized in respect to spectroscopic property, polymer morphology and particles size distribution. It was found that the type of cross-linker and amount of solvent have significant effect on particles size and morphology. A prominent necklace-like structure that enabled the polymer nanoparticles to have a good dispersibility could be obtained by using trimethylolpropane trimethacrylate/divinylbenzene (TRIM/DVB) as the cross-linker. Moreover, the BODIPY based polymers exhibited much stronger fluorescence than BODIPY monomer in aqueous solution, especially with the smaller nanoparticles. The fluorescent polymer nanoparticle preparation proposed in this study can be a good choice for addressing the limitation of hydrophobic BODIPY dyes applications in the water-based biomedical media.

Theoretical Investigation of the Circularly Polarized Luminescence of a Chiral Boron Dipyrromethene (BODIPY) Dye.

Over the last decade, molecules capable of emitting circularly polarized light have attracted growing attention for potential technological and biological applications. The efficiency of such devices depend on multiple parameters, in particular the magnitude and wavelength of the peak of emitted light, and also on the dissymmetry factor for chiral applications. In light of these considerations, molecular systems with tunable optical properties, preferably in the visible spectral region, are particularly appealing. This is the case of boron dipyrromethene (BODIPY) dyes, which exhibit large molecular absorption coefficients, have high fluorescence yields, are very stable, both thermally and photochemically, and can be easily functionalized. The latter property has been extensively exploited in the literature to produce chromophores with a wide range of optical properties. Nevertheless, only a few chiral BODIPYs have been synthetized and investigated so far. Using a recently reported axially chiral BODIPY derivative where an axially chiral BINOL unit has been attached to the chromophore unit, we present a comprehensive computational protocol to predict and interpret the one-photon absorption and emission spectra, together with their chiroptical counterparts. From the physico-chemical properties of this molecule, it will be possible to understand the origin of the circularly polarized luminescence better, thus helping to fine-tune the properties of interest. The sensitivity of such processes require accurate results, which can be achieved through a proper account of the vibrational structure in optical spectra. Methodologies to compute vibrationally-resolved electronic spectra can now be applied on relatively large chromophores, such as BODIPYs, but require more extensive computational protocols. For this reason, particular attention is paid in the description of the different steps of the protocol, and the potential pitfalls. Finally, we show how, by means of appropriate tools and approaches, data from intermediate steps of the simulation of the final spectra can be used to obtain further insights into the properties of the molecular system under investigation and the origin of the visible bands.

A Palette of Efficient and Stable Far-Red and NIR Dye Lasers

The disposal of long-wavelength-emitting sources is of paramount relevance in technology and biophotonics due to the low interference with the surroundings that these kinds of far-red and near-infrared radiations hold. As a result of the continued efforts carried out during the last few years by our research group to design new boron-dipyrromethene (BODIPY) dyes with improved photonic performance, two approaches were tested to develop a new generation of organic dyes able to display efficient and long-lasting laser emission in both target spectral regions. On the one hand, the annulation of aromatic benzofuran at the dipyrrin backbone leads to conformationally restricted dyes yielding photostable and bright laser emission beyond 600 nm at the far-red spectral region. On the other hand, a more pronounced shift to longer wavelengths reaching 725 nm at the near-infrared region is feasible, while keeping a reasonably high laser efficiency and tolerance to prolonged and intense pumping, based on aza-BODIPYs bearing peripheral aryl rings. These two complementary strategies yield a library of laser-emitting compounds comprising the 600–725 nm spectral region. Moreover, their laser performance is better than the commercially available dye lasers active in this spectral window.

Light-Activated Carbon Monoxide Prodrugs Based on Bipyridyl Dicarbonyl Ruthenium(II) Complexes.

Two photoactivatable dicarbonyl ruthenium(II) complexes based on an amide‐functionalised bipyridine scaffold (4‐position) equipped with an alkyne functionality or a green‐fluorescent BODIPY (boron‐dipyrromethene) dye have been prepared and used to investigate their light‐induced decarbonylation. UV/Vis, FTIR and 13C NMR spectroscopies as well as gas chromatography and multivariate curve resolution alternating least‐squares analysis (MCR‐ALS) were used to elucidate the mechanism of the decarbonylation process. Release of the first CO molecule occurs very quickly, while release of the second CO molecule proceeds more slowly. In vitro studies using two cell lines A431 (human squamous carcinoma) and HEK293 (human embryonic kidney cells) have been carried out in order to characterise the anti‐proliferative and anti‐apoptotic activities. The BODIPY‐labelled compound allows for monitoring the cellular uptake, showing fast internalisation kinetics and accumulation at the endoplasmic reticulum and mitochondria.

Macrocyclic Arenes Functionalized with BODIPY: Rising Stars among Chemosensors and Smart Materials

Macrocycles play a crucial role in supramolecular chemistry and the family of macrocyclic arenes represents one of the most important types of hosts. Among them, calixarenes, resorcinarenes and pillararenes are the most commonly encountered macrocyclic arenes, and they have received considerable attention. Boron-dipyrromethene (BODIPY) dyes are fascinating compounds with multiple functionalization sites and outstanding luminescence properties including high fluorescence quantum yields, large molar absorption coefficients and remarkable photo- and chemical stability. The combination of macrocyclic arenes and BODIPY dyes has been demonstrated to be an effective strategy to construct chemosensors for various guests and smart materials with tailored properties. Herein, we firstly summarize the recent advances made so far in macrocyclic arenes substituted with BODIPY. This review only focuses on the three macrocyclic arenes of calixarenes, resorcinarenes and pillararenes, as there are no other macrocyclic arenes substituted BODIPY units at the present time. Hopefully, this review will not only afford a guide and useful information for those who are interested in developing novel chemosensors and smart materials, but also inspire new opportunities in this field.

Visible Light Excitation of BODIPYs Enables Dehydrogenative Enamination at Their α-Positions with Aliphatic Amines.

A photoredox-mediated route to enamination of boron dipyrromethene (BODIPY) dyes with aliphatic amines is reported by activating both the β-C(sp3)-H bond of amines and the α-C(sp2)-H bond of BODIPYs under visible light illumination. Dehydrogenation of amines by excited-state BODIPYs and/or photoredox catalyst gave enamine intermediates, which were further trapped by BODIPYs to give a series of α-enamineBODIPYs. These resultant α-enamineBODIPYs showed red-shifted absorption and emission maxima with ratiometric pH-dependent fluorescence.