Synthesis, structure and properties of thiophene-fused BODIPYs and azaBODIPYs as near-infrared agents

Annulation of thiophene to the BODIPY/aza-BODIPY core showed a significant impact on the spectral properties of the resulting scaffolds.

Non-symmetric benzo[b]-fused BODIPYs as a versatile fluorophore platform reaching the NIR: a systematic study of the underlying structure–property relationship

Ten newly synthesized non-symmetric benzo[b]-fused BODIPYs are compared with an extended series of nine related families (23 compounds) to gain insights into their structure–property relationship.

Naphthalene-fused BODIPY near-infrared dye as a stable contrast agent for in vivo photoacoustic imaging

Naphthalene-fused BODIPY near infrared dye (Na-BD) was synthesized and used as a stable contrast agent for in vivo photoacoustic imaging.

Synthesis, structure and photophysical properties of near-infrared 3,5-diarylbenzoBODIPY fluorophores

An efficient synthetic method for 3,5-diarylbenzoBODIPYs was reported, which showed tunable absorption/emission via the variation of the 3,5-aryl substituents.

Improving the Accuracy of Excited-State Simulations of BODIPY and Aza-BODIPY Dyes with a Joint SOS-CIS(D) and TD-DFT Approach

BODIPY and aza-BODIPY dyes constitute two key families of organic dyes with applications in both materials science and biology. Previous attempts aiming to obtain accurate theoretical estimates of their optical properties, and in particular of their 0-0 energies, have failed. Here, using time-dependent density functional theory (TD-DFT), configuration interaction singles with a double correction [CIS(D)], and its scaled-opposite-spin variant [SOS-CIS(D)], we have determined the 0-0 energies as well as the vibronic shapes of both the absorption and emission bands of a large set of fluoroborates. Indeed, we have selected 47 BODIPY and 4 aza-BODIPY dyes presenting diverse chemical structures. TD-DFT yields a rather large mean signed error between the experimental and theoretical 0-0 energies with a systematic overshooting of the transition energies (by ca. 0.4 eV). This error is reduced to ca. 0.2 [0.1] eV when the TD-DFT 0-0 energies are corrected with vertical CIS(D) [SOS-CIS(D)] energies. For BODIPY and aza-BODIPY dyes, both CIS(D) and SOS-CIS(D) clearly outperform TD-DFT. The present computational protocol allows accurate data to be obtained for the most relevant properties, that is, 0-0 energies and optical band shapes.

Synthesis and Properties of Benzothieno[b]-Fused BODIPY Dyes

Two benzothieno[b]-fused BODIPYs, BT-BODIPY and BBT-BODIPY, in which one parent BODIPY core is fused with one and two benzothieno rings, respectively, were synthesized from BODIPYs substituted with 2-(methylsulfinyl)phenyl at the β-position. The first H2SO4-induced cyclization and deborylation afforded benzothieno[b]-fused dipyrrin derivatives, which can easily complex with BF3·OEt2 to form the desired benzothieno[b]-fused BODIPYs. It was revealed that the fusion of the benzothieno ring is more effective at extending conjugation than simple attachment of the 2-(methylthio)phenyl substituent, which presumably results from conformational restriction. Compared with the corresponding unstrained SPh-BODIPY and BSPh-BODIPY, which contain one and two 2-(methylthio)phenyl groups at the β-position, BT-BODIPY and BBT-BODIPY display red shifted absorption, increased absorptivity, and fluorescence efficiency. Furthermore, the ring fusion is also helpful to increase stability of the formed cation in BBT-BODIPY. Thus, BBT-BODIPY exhibits very intriguing properties, such as intense absorption and emission in the red region, very sharp emission spectra, and reversible oxidation and reduction potentials.

Dye chemistry with time-dependent density functional theory

In this perspective, we present an overview of the determination of excited-state properties of "real-life" dyes, and notably of their optical absorption and emission spectra, performed during the last decade with time-dependent density functional theory (TD-DFT). We discuss the results obtained with both vertical and adiabatic (vibronic) approximations, choosing relevant examples for several series of dyes. These examples include reproducing absorption wavelengths of numerous families of coloured molecules, understanding the specific band shape of amino-anthraquinones, optimising the properties of dyes used in solar cells, mimicking the fluorescence wavelengths of fluorescent brighteners and BODIPY dyes, studying optically active biomolecules and photo-induced proton transfer, as well as improving the properties of photochromes.

Far-red and near infrared BODIPY dyes: synthesis and applications for fluorescent pH probes and bio-imaging

Far-red and near infrared (NIR) emissive dyes have advantages in the development of fluorescent probes and labelling for bio-imaging in living systems since fluorescence in the long-wavelength region would generate minimum photo-toxicity to biological components, deep tissue penetration and minimal background from auto-fluorescence by bio-molecules. BODIPY dyes are attractive due to their excellent photo-physical properties and potential for fluorescence-based sensing and bio-imaging applications. Thus, numerous research papers have emerged to develop BODIPY-based dyes with absorption and emission in the long-wavelength spectral region (650-900 nm). This review summarizes the general strategies to obtain far-red and NIR BODIPYs. Moreover, their applications for fluorescent pH probes and imaging or labelling in living systems are highlighted.

Fusion and planarization of bisBODIPY: a new family of photostable near infrared dyes

A new family of directly-fused bisBODIPY BBP was developed by fusion and planarization of bisBODIPY 4 through a FeCl₃-mediated intramolecular oxidative cyclodehydrogenation reaction, showing intriguing electrochemical and spectroscopic properties.

AIE-active organoboron complexes with highly efficient solid-state luminescence and their application as gas sensitive materials

Four benzothiazole–ketoiminate-based organoboron complexes were demonstrated to show aggregation-induced emission, a large Stokes shift and high quantum yield in the solid-state, which were rationalized through X-ray crystal analysis, and electronic structure calculations.

Switching of the triplet excited state of styryl 2,6-diiodo-bodipy and its application in acid-activatable singlet oxygen photosensitizing

IodoBodipy-styrylBodipy dyads triplet photosensitizers were prepared (B-1 and B-2) which contain acid-responsive moiety. Both compounds show broadband visible light absorption, due to the resonance energy transfer (RET) between the two different visible light-harvesting Bodipy units. The photophysical properties of the dyads were studied with steady-state and nanosecond time-resolved transient absorption spectroscopy. The production of triplet excited state is switched ON or OFF by protonation/deprotonation of the amino group in the dyads. In the neutral form, the excited state is short-lived (<10 ns) and no singlet oxygen ((1)O2) photosensitizing was observed. Upon protonation, a long-lived triplet excited state was observed (τT = 3.1 μs) and the (1)O2 quantum yield (ΦΔ) is up to 73.8%. The energy levels of the components of the dyads were changed upon protonation and this energy level tuning exerts significant influence on the triplet state property of the dyad. Acid-activated shuffling of the localization of the triplet excited state between two components of a dyad was observed. Furthermore, we observed a rare example that a chromophore giving shorter absorption wavelength is acting as the singlet energy acceptor in RET. The experimental results were rationalized by density functional theory (DFT) and time-dependent DFT (TDDFT) calculations.

NIR-fluorescent coumarin-fused BODIPY dyes with large Stokes shifts

A series of novel non-symmetrical coumarin-fused BODIPY dyes were synthesised. Their absorption and emission properties are strongly influenced by substitution in the coumarin moiety. Diethylamino-substituted dyes showed near-IR emission with large Stokes shifts (up to 144 nm) and good fluorescence quantum yields.

Highly fluorescent BF2 complexes of hydrazine-Schiff base linked bispyrrole

A series of BF2 complexes of hydrazine-Schiff base linked bispyrrole have been prepared from a simple two-step reaction from commercially available substances and are highly fluorescent in solution, film, and solid states with larger Stokes shift and excellent photostabilities comparable or even super to those of their BODIPY analogues. These resultant fluorescent dyes are highly susceptible to the postfunctionalization, as demonstrated in this work via the Knoevenagel condensation to introducing functionalities or tether groups to the chromophore.

Bis-naphthobipyrrolylmethene derived BODIPY complex: an intense near-infrared fluorescent dye

Synthesis of a novel π-extended BODIPY derived from naphthobipyrrole is presented. This dye molecule displays very intense near-infrared (NIR) absorption (ε > 400,000 M(-1) cm(-1)) and emission bands (>700 nm), accompanied by high quantum yield (φf = 0.65) owing to its extended π-conjugation along with imposed structural rigidification.

meso-Ester and carboxylic acid substituted BODIPYs with far-red and near-infrared emission for bioimaging applications

A series of meso-ester-substituted BODIPY derivatives 1-6 are synthesized and characterized. In particular, dyes functionalized with oligo(ethylene glycol) ether styryl or naphthalene vinylene groups at the α positions of the BODIPY core (3-6) become partially soluble in water, and their absorptions and emissions are located in the far-red or near-infrared region. Three synthetic approaches are attempted to access the meso-carboxylic acid (COOH)-substituted BODIPYs 7 and 8 from the meso-ester-substituted BODIPYs. Two feasible synthetic routes are developed successfully, including one short route with only three steps. The meso-COOH-substituted BODIPY 7 is completely soluble in pure water, and its fluorescence maximum reaches around 650 nm with a fluorescence quantum yield of up to 15 %. Time-dependent density functional theory calculations are conducted to understand the structure-optical properties relationship, and it is revealed that the Stokes shift is dependent mainly on the geometric change from the ground state to the first excited singlet state. Furthermore, cell staining tests demonstrate that the meso-ester-substituted BODIPYs (1 and 3-6) and one of the meso-COOH-substituted BODIPYs (8) are very membrane-permeable. These features make these meso-ester- and meso-COOH-substituted BODIPY dyes attractive for bioimaging and biolabeling applications in living cells.

Structural modification strategies for the rational design of red/NIR region BODIPYs

The structure–property relationships of red/NIR region BODIPY dyes is analyzed, so that trends in their photophysical properties can be readily compared.

Yellow NIR dye: π-fused bisbenzoBODIPYs with electron-withdrawing groups

Stable benzene-fused bisbenzoBODIPY with four cyano groups is ideal for a NIR-selective dye, which shows strong absorption in the NIR region and good transparency in the visible region.