Boron-dipyrromethene Molecules Research Articles

Producing circularly polarized luminescence by radiative energy transfer from achiral metal-organic cage to chiral organic molecules

The development of circularly polarized luminescence (CPL) materials with high performance is significantly important. Herein, we develop a facial strategy for fabricating a CPL-active system by employing an achiral luminescent metal-organic cage (MOC) and chiral boron dipyrromethene (BODIPY) molecules. CPL is achieved by taking advantage of the radiative energy transfer process, in which BODIPY molecules act as energy acceptors and MOCs act as donors. The CPL performance (maximum luminescence dissymmetry factor up to ±1.5×10−3) can be tuned by adjusting the ratio between MOCs and BODIPY. White-light emission with the CPL feature is obtained by using a ternary system including MOC, chiral BODIPY, and Rhodamine B. The present work provides a facile and universal strategy to construct a CPL-active system by integrating achiral luminophores and chiral molecules.

Effect of Alkyl Chain Length on Current‐Voltage Characteristics of BODIPY Molecules Deposited on Si(n++) Substrates

AbstractDespite having good electronic properties, BODIPY (boron dipyrromethene) and its derivatives attract less research attention towards the development of BODIPY based molecular electronics. Here we have investigated the effect of alkyl chain length attached to BODIPY molecule on its diode and negative differential behaviour. An undecenyl‐BODIPY dye (BODIPY‐C11) was designed, synthesized and deposited on Si (111) surface which was further converted into a bilayer using another BODIPY dye, PM567. Various techniques were used to check the arrangement and thickness of the layers which established that the designed molecule is suitable for compact grafting on Si surface. Electrical behaviour of BODIPY‐C11 monolayer and bilayer showed rectification (rectification ratio=500) and NDR property (peak‐to‐valley ratio=1000), respectively with improved device performances as compared to the electrical characteristics shown by 2,6‐diethyl‐4,4‐difluoro‐1,3,5,7‐tetramethyl‐8‐(4’‐(4”‐penteneoxyphenyl)‐4‐bora‐3a,4a‐diaza‐s‐indecene (BODIPY‐C5) grafted on Si. This study established that the electrical behaviour of BODIPY can be modulated by simply changing the alkyl chain length, which will be useful for the development of BODIPY‐based electronic materials.

Development of Meso‐Substituted Heterocyclic BODIPY‐Based Polymeric Nanoparticles for Pathogen Inhibition using Photodynamic Therapy**

AbstractIn this work, a series of novel small fluorophores, meso‐substituted heterocyclic BODIPYs were designed and synthesized as phototherapeutic agents. Boron dipyrromethene (BODIPY) dyes are promising chromophores and currently used as a sensitizers in photodynamic therapy (PDT). However, BODIPY as an organic photosensitizer (PS), suffers from poor hydrophilicity resulting in low efficiency in biological applications. To overcome these problems, biopolymer (gelatin) based nanoparticles are developed to incorporate BODIPYs, to achieve phototherapeutic nanoagents (BODIPY‐GNPs) in the aqueous system. More importantly, BODIPY‐GNPs have better in vitro physicochemical properties in the aqueous medium than native BODIPYs. The BODIPY‐GNPs were further explored for their photo‐inhibition activity towards Gram‐positive and Gram‐negative bacteria and fungi using LED as the light source. These BODIPY molecules also showed the ability to intercalate the DNA in vitro. This study provides a new avenue to design therapeutic agents for biomedical applications in photodynamic therapy.

Front Cover Picture: Stereoselective Cyclopropanation of Boron Dipyrromethene (BODIPY) Derivatives by an Organocascade Reaction (Adv. Synth. Catal. 5/2022)

The front cover picture illustrates the stereoselective synthesis of BODIPY molecules, in connection to the stereo audio player with the inscription “stereo bodipy.” The BODIPY molecule is inserted by a robot symbolizing the simplicity of preparation of such molecules. The synthesis of enantiopure chiral BODIPY molecules is of importance due to their intrinsic properties as fluorophores that could be used as probes for molecular sensing. The cover image was created by Tomáš Belloň. Details can be found in the Research Article by Veselý and co-workers (V. Dočekal, T. Koberová, J. Hrabovský, A. Vopálenská, R. Gyepes, I. Císařová, R. Rios, J. Veselý, Adv. Synth. Catal. 2022, 364, 930–937; DOI: 10.1002/adsc.202101286).

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.

Coherent internal conversion from high lying electronic states to S1 in boron-dipyrromethene derivatives.

Internal conversion is the first step after photoexcitation to high lying electronic states, and plays a central role in many photoinduced processes. In this report, we demonstrate a truly ultrafast internal conversion (IC) in large molecules by time-resolved fluorescence (TF). Following photoexcitation to the Sn (n ≥ 2) state, TF of the S1 state was recorded for two boron-dipyrromethene (BODIPY) derivatives in solution. IC to S1 takes place nearly instantaneously within 20 fs for both molecules. Abundant nuclear wave packet motions in the S1 state are manifest in the TF signals, which demonstrates that the IC in these BODIPY molecules is coherent with respect to most of the vibrational modes. Theoretical calculations assuming impulsive IC to S1 account for the wave packet dynamics accurately.

Fluorescent macromolecular chemosensors for highly and selectively detecting of 2, 4, 6-trinitrophenol

Among nitroaromatic compounds with similar structures, 2,4,6-trinitrophenol (TNP) exhibits strong biological toxicity and explosion hazard. Therefore, detection of TNP is of great importance. In this work, two novel fluorescent macromolecular chemosensors P1 and P2 were prepared using boron-dipyrromethene (BODIPY) as the fluorophore. After the preparation of small BODIPY molecule M1, another small molecule M2 with two aldehyde groups was synthesized by two consecutive Vilsmeier-Haack reactions. Then, M2 reacts with trans-cyclohexane-1,4-diamine and 1,4-phenylenediamine respectively to obtain two macromolecules P1 and P2 via Schiff Base forming reaction. The results suggested that P1 and P2 could recognize TNP only while other aromatic/nitroaromatic compounds cannot cause significant fluorescence intensity response. When TNP exist, these fluorescent macromolecular chemosensors produce significant fluorescence quenching. At the same time, because the electron-rich Schiff base and the electron-deficient TNP have the structural basis of chemical interaction, these two macromolecular sensors also have excellent sensitivity to TNP, and the excellent recognition limit of detection reach as low as 0.017 μM. High sensitivity and selectivity have been applied to test TNP in lake water samples as well.

Unveiling the Photophysical Properties of Boron-dipyrromethene Dyes Using a New Accurate Excited State Coupled Cluster Method.

Boron-dipyrromethene (BODIPY) molecules form a class of fluorescent dyes known for their exceptional photoluminescence properties. Today, they are used extensively in various applications from fluorescent imaging to optoelectronics. The ease of altering the BODIPY core has allowed scientists to synthesize dozens of analogues by exploring chemical substitutions of various kinds or by increasing the length of conjugated groups. However, predicting the impact of any chemical change accurately is still a challenge, especially as most computational methods fail to describe correctly the photophysical properties of BODIPY derivatives. In this study, the recently developed coupled cluster method called "domain-based local pair natural orbital similarity transformed equation of motion-coupled cluster singles and doubles" (DLPNO-STEOM-CCSD) is employed to compute the lowest vertical excitation energies of more than 50 BODIPY molecules. The method performs remarkably well yielding an accuracy of about 0.06 eV compared to the experimental absorption maxima. We also provide an estimate to the error made by neglecting vibronic effects in the computed spectra. The dyes selected for investigation here span a large range of molecular sizes and chemical functionalities and are embedded in solvents with different polarities. We have also investigated if the method is able to correctly reproduce the impact of a single chemical modification on the absorption energy. To characterize the method in more specific terms, we have studied four large BODIPY analogues used in real-life applications due to their interesting chemical properties. These examples should illustrate the capacity of the DLPNO-STEOM-CCSD procedure to become a method of choice for the study of photophysical properties of medium to large organic compounds.

Boron Dipyrromethene Nano-Photosensitizers for Anticancer Phototherapies.

As traditional phototherapy agents, boron dipyrromethene (BODIPY) photosensitizers have attracted increasing attention due to their high molar extinction coefficients, high phototherapy efficacy, and excellent photostability. After being formed into nanostructures, BODIPY-containing nano-photosensitizers show enhanced water solubility and biocompatibility as well as efficient tumor accumulation compared to BODIPY molecules. Hence, BODIPY nano-photosensitizers demonstrate a promising potential for fighting cancer. This review contains three sections, classifying photodynamic therapy (PDT), photothermal therapy (PTT), and the combination of PDT and PTT based on BODIPY nano-photosensitizers. It summarizes various BODIPY nano-photosensitizers, which are prepared via different approaches including molecular precipitation, supramolecular interactions, and polymer encapsulation. In each section, the design strategies and working principles of these BODIPY nano-photosensitizers are highlighted. In addition, the detailed in vitro and in vivo applications of these recently developed nano-photosensitizers are discussed together with future challenges in this field, highlighting the potential of these promising nanoagents for new tumor phototherapies.

S2 and mixed aggregate state emission of thiophene-BODIPY

Boron dipyrromethene (BODIPY) being a chromophoric dye molecule has been extensively studied in dye sensitized solar cell (DSSC), imaging, and dye laser application. BODIPY is a stable boron complex with a broad absorption and photoluminescence (PL) in the visible region of solar radiation. This class of molecules show anomalous photophysical properties, which varies with concentration of the molecule. Here, we report the thorough analysis of photophysical study after synthesized the BODIPY molecule, which made up of two thiophene BODIPY cores comprising a phenyl spacer in between, coded as TG2 dye molecule. Steady state and time resolved concentration dependent PL reveal that, at very low concentration (nM) TG2 shows both S1 (first excited state) and S2 (second excited state) PL. Importantly, at higher concentration (mM) TG2 found to exist in aggregated state. Optical absorption and PL studies confirmed that TG2 exists in mixture of J-/H- aggregate state. Moreover, femtosecond transient absorption (fs-TA) analysis has been studied following 400 nm optical pump, which reveals that the excited singlet state converted to the mixed aggregated state with in an average time constant of 6 ps.

Dark Field Scattering Spectroelectrochemistry of Single Au Nanoparticles at Transparent Planar and Micro-Sized Electrodes

Boron dipyrromethene (BODIPY) molecules with donor-acceptor configurations are of great interests for harvesting and converting solar energy in a solar cell. Au nanoparticles have been applied to enhance solar energy harvesting and conversion efficiency of organic solar cells because of their surface plasmon properties for increasing light absorption cross-section of an organic dye. Electrochemical properties of single BODIPY dyes and plasmonic Au nanoparticles (NPs) are studied using combined optical and electrochemical methods to reveal their structure-function relationship at the nanometer scale. Our study shows a heterogeneous half redox potential distribution for the BODIPY molecules embedded in polystyrene film because of the heterogeneity in their charge transfer rates. Single molecules adsorbed onto a TiO2 surface with ordered nanostructures show surprising fluorescence blinking activity with the shortest ON duration time in comparison to bare glass and indium-doped tin oxide (ITO) surfaces. Dark field scattering (DFS), photoluminescence (PL), and electrogenerated chemiluminescence (ECL) are used to probe local redox reactions of single Au nanoparticles at transparent planar and micro-sized electrode. Our study shows that these optical responses at individual plasmonic NPs are strongly dependent on particle size, and are affected by the local chemical and charge transfer environment of the NPs.

Photoswitchable Near-Infrared-Emitting Boron-dipyrromethene (BODIPY) Nanoparticles

The reversible photoswitched near-infrared-(NIR)-emitting Boron-dipyrromethene (BODIPY) containing nanparticles are reported. Dithienylethene derivatives are used as the photochromic unit in the nanoparticle to control the on and off of fluorescence BODIPY molecules. As a result, it is demonstrated that these nanoparticles conduct robust reversible modulation of the NIR fluorescence in vitro and in the cell culture with negligible toxicity. This study may offer a new approach to the use of these nanomaterials for numerous photonic and biophotonic applications.

A simple and efficient protocol for screening boron-dipyrromethene dyes using TD-DFT and an examination of the aryl-meso position

BMK (Boese-Martin for Kinetics) and CAM-B3LYP (coulomb-attenuating method-Becke, 3-parameter, Lee-Yang-Parr) are evaluated as functionals in the calculation of the absorption wavelengths of boron dipyrromethene (BODIPY) fluorescent dyes using time-dependent density functional theory (TD-DFT). We discovered that a computational protocol using CAM-B3LYP/cc-pVTZ//B3LYP/6-31G∗ with a polarization-continuum model (PCM) was able to predict the absorption wavelengths of BODIPY compounds and matched experimental measurements fairly well when an empirical correction was applied with an average error of 7.1nm. Then, using our computational protocol, we synthesized a few novel BODIPY compounds in which we were able to explore the effect of substitution to an aryl-meso ring on BODIPY compounds and confirmed a small effect on the λmax for these compounds which was able to modify the absorbance up to 10nm. Based on these findings, modifications at the aryl-meso position are insufficient to cause large enough bathochromic shifts in the main spectral band to move the absorbance band of BODIPY molecules into the near-IR range.

Rational Engineering of BODIPY-Bridged Trisindole Derivatives for Solar Cell Applications.

Boron dipyrromethene (BODIPY) and its derivatives are known to be efficient photon-harvesting chromophores. However, their study as active materials in bulk heterojunction (BHJ) solar cells is still scarce. In this study, the development of new synthetic ways to design original BODIPY-based dumbbell-shape molecules, including a first 2,3,5,6-tetravinyl aromatic BODIPY molecule, is reported. High fill factors can be obtained in BHJ solar cells when blended with a fullerene derivative, leading to a new record BODIPY-based power conversion efficiency of 5.8 %.

BODIPY star-shaped molecules as solid state colour converters for visible light communications

In this paper, we study a family of solid-state, organic semiconductors for visible light communications. The star-shaped molecules have a boron-dipyrromethene (BODIPY) core with a range of side arm lengths which control the photophysical properties. The molecules emit red light with photoluminescence quantum yields ranging from 22% to 56%. Thin films of the most promising BODIPY molecules were used as a red colour converter for visible light communications. The film enabled colour conversion with a modulation bandwidth of 73 MHz, which is 16 times higher than that of a typical phosphor used in LED lighting systems. A data rate of 370 Mbit/s was demonstrated using On-Off keying modulation in a free space link with a distance of ∼15 cm.

Comparison study of electrochemiluminescence of boron-dipyrromethene (BODIPY) dyes in aprotic and aqueous solutions

Boron-dipyrromethene (BODIPY) dye molecules are well known for their excellent absorption and emission optical properties. Here, we report the results of an electrochemical and electrochemiluminescence (ECL) study of an organic-soluble and a water-soluble BODIPY dye to explore their effectiveness as ECL luminophores. A combination of UV–visible, fluorescence, and spooling ECL spectroscopy was used to study the mechanisms of ECL light emission. It was discovered that excimers, the excited states of analyte dimers, contributed significantly to the production of ECL. These BODIPY molecules exhibited relatively weak ECL efficiencies following the annihilation mechanism. However, ECL was enhanced with co-reactants such as persulfate, and tri-n-propylamine. Spooling ECL spectroscopy was utilized to gain analytical insight into light emission mechanisms. It is shown that while these two BODIPY compounds can form photoinduced excited monomers, excimers were generated mainly in their co-reactant ECL pathways.

Synthesis and Characterization of Far-Red/NIR-Fluorescent BODIPY Dyes, Solid-State Fluorescence, and Application as Fluorescent Tags Attached to Carbon Nano-onions.

A series of π-extended distyryl-substituted boron dipyrromethene (BODIPY) derivatives with intense far-red/near-infrared (NIR) fluorescence was synthesized and characterized, with a view to enhance the dye's performance for fluorescence labeling. An enhanced brightness was achieved by the introduction of two methyl substituents in the meso positions on the phenyl group of the BODIPY molecule; these substituents resulted in increased structural rigidity. Solid-state fluorescence was observed for one of the distyryl-substituted BODIPY derivatives. The introduction of a terminal bromo substituent allows for the subsequent immobilization of the BODIPY fluorophore on the surface of carbon nano-onions (CNOs), which leads to potential imaging agents for biological and biomedical applications. The far-red/NIR-fluorescent CNO nanoparticles were characterized by absorption, fluorescence, and Raman spectroscopies, as well as by thermogravimetric analysis, dynamic light scattering, high-resolution transmission electron microscopy, and confocal microscopy.