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By changing benzo-fused position on pyridyl unit, three aza boron-pyridyl-isoindoline isomers, a new type of BODIPY analog, are synthesized through a facile two step reaction. These isomers show broad envelopes of intense vibrational bands in the absorption and emission spectra with moderate fluorescence quantum yields. In comparison to those of classical BODIPYs, significant fluorescence intensity are observed for these isomers in film and powder. An analysis of the structure-property relationships has been carried out based on X-ray crystallography, optical spectroscopy, and theoretical calculation.

BODIPY and aza-BODIPY fluorophores linked to steroids are being developed as multimodal-imaging agents to monitor the mechanism of action of biologically active components in living systems.

Selective fluorescent and colorimetric sensing of cysteine in methanol-HEPES buffer (45 mM, pH $=$ 7.2, v/v $=$ 1/1) solution over various common amino acids and related thiol containing compounds has been achieved based on the cyclization reaction between the formyl group on 3-formylBODIPYs and cysteine/homocystein. Upon addition of cysteine/homocystein, 3-formylBODIPYs exhibited greatly enhanced fluorescence intensity as well as an abvious red-shift of the absorption peak (20–30 nm). The detection limits for cysteine were in the range of 1.18–2.73 $\times$10${}^{-6}$ M. The detection mechanism was studied by nuclear magnetic resonance and theoretical calculation.

A series of meso-aryloxy linked BODIPY monomers, dimers and trimer were synthesized by nucleophilic aromatic substitution (S_NAr) reaction from phenols with meso-chloro BODIPY and their photophysical properties were systematically studied by UV-vis and fluorescence spectroscopy. The relationship between their photophysical properties and the spatial arrangement of meso-aryloxy linked BODIPYs has been discussed. The monomers exhibited different extent solvent-dependent fluorescence, and fluorescence quenching in polar solvents were found relative to the HOMO energies of the donor (meso-phenols), indicating possible PET effect from meso-phenols to the BODIPY fluorophore. Ortho-dimer showed unusual broad red-shifted emission bands centered at 550 nm with a larger Stokes shifts at the range of 2900–3400 cm${}^{-1}$, and low fluorescence quantum yields, which was in sharp contrast to those of other dimers and trimer, indicating of possible excimeric species formation due to slipped cofacial arrangement ofortho-dimer.

A series of boron dipyrromethene (BODIPY) dyes with properties that are ideal for a good photosensitizer have been prepared. Functionalization with bromine atoms and attachment to gold nanoparticles through a meso-aniline group results in high singlet oxygen quantum yields and low fluorescent quantum yields. Molecular modelling was used to analyze trends in the MO energies of various brominated aniline BODIPY dyes.

A series of boron-functionalized BODIPY dyes with cyano groups were prepared from their corresponding BF₂ derivatives using SnCl₄/TMSCN at room temperature for 10 min. Replacement of the fluorines by cyano groups reduces the B–N bond lengths, decreases the charge on boron, and causes characteristic ${}^{11}$B NMR chemical shifts. The 4,4${}^{\prime }$-dicyano-BODIPYs show significantly enhanced stability to acidic conditions (excess TFA) and, with one exception, enhanced fluorescence quantum yields. Furthermore, the B(CN)₂-BODIPYs were non-cytotoxic to HEp2 cells, both in the dark and upon exposure to light (1.5 J/cm${}^2)$, and rapidly accumulated within cells, localizing mainly in the lysosomes, ER and Golgi.

A star-shaped molecule was designed and synthesized based on a known central truxene platform. Two BODIPY derivatives and one corrole macrocycle were introduced and connected to the 2, 7 and 12-positions of the truxene unit by Suzuki coupling. The dyad was fully characterized by UV-vis absorption, proton nuclear magnetic resonance, mass spectrometry. The direction of energy transfer upon electronic excitation was explored, and the star-shaped molecule system exhibits a highly efficient photoinduced energy transfer process from the excited BODIPY part to the corrole unit.

Regioselective functionalization of core per-substituted boron dipyrromethenes (BODIPYs) has been achieved efficiently based on tetrabromoBODIPY, which affords a series of dibenzofuran-fused chromophores, via a regioselective nucleophilic substitution reaction followed by direct palladium-catalyzed two-fold intramolecular ring fusion. These rigid dibenzofuran-fused BODIPYs showed impressive photophysical properties such as clearly red-shifted absorption and emission bands, enhanced absorption coefficients upon and intense fluorescence (close to unity).

Two novel quinoxaline-bridged bisBODIPYs have been synthesized by the condensation of 2,3-bis(5-formylpyrrol-2-yl)quinoxaline with 3-ethyl-2,4-dimethylpyrrole followed by a modification using a Knoevenagel reaction. They were well characterized by X-ray diffraction, NMR, HRMS UV-vis and fluorescence spectroscopy. These two quinoxaline-bridged bisBODIPYs have unusual broad absorption bands, which are different from those of typical BODIPYs They exhibit broad red-shifted emission bands centered at around 610 nm and 730 nm respectively with larger Stokes shifts at the range of 1421–2136 cm${}^{\mathrm{\text{-1}}}$ Both bisBODIPYs show different extent solvent-dependent fluorescence and exhibit fluorescence quenching in polar solvents due to the existence of possible intramolecular charge transfer.

Two boron-dipyrromethene dyes bearing a conjugated guanine unit (G-BODIPYs) 1 and 2 were synthesized and fully characterized. The self-assembly properties of these dyes were investigated by X-ray crystallography, ${}^{\mathrm{\text{1}}}$H NMR and UV-vis spectroscopy. As revealed by X-ray crystal structure studies, G-BODIPY 1 self-assembled into ribbon-like structures due to the intermolecular hydrogen bonding and $\pi$–$\pi$ stacking interaction. Concentration-dependent ${}^{\mathrm{\text{1}}}$H NMR experiments confirmed the formation of hydrogen bonds of the guanine units in solution for both dye 1 and 2. In the presence of K${}^{\mathrm{\text{+}}}$, the characteristic signals for the formation of cyclic G-quadruplex structures were observed in the ${}^{\mathrm{\text{1}}}$H NMR study. Aggregation of G-BODIPY dyes was further monitored by UV-vis absorption spectroscopy by varying the solvent polarity and temperature. H-type aggregates of dye 1, which was characterized by a new hypsochromically shifted absorption band with ${\lambda }_{\mathrm{\text{max}}}=$ 461 nm, was obtained. In the presence of K${}^{\mathrm{\text{+}}}$, the enhancement of stability was observed for the H-aggregates of dye 1.

Fluorescence and SPECT/PET imaging are powerful tools currently in use by the scientific community and receiving a great attention for the development of dual-modality imaging agents. BODIPYs are among the most promising candidates to be used for such functions due their excellent absorbance and fluorescence properties as well as their ease of radiolabeling without compromising their biological properties. In this manuscript we present an overview of BODIPY radiolabeling methods and their relevance to the development of multimodality agents.

Photodynamic therapy (PDT) is a minimally invasive technique for the treatment of target malignant tumors via the generation of highly reactive singlet oxygen species. PDT treatment of cancer/tumor tissues greatly relies on the development of suitable stable, highly specific and efficient photosensitizers. BODIPY (Boron dipyrromethene) derivatives, as a class of well-developed, versatile fluorescent dyes, has emerged as a new class of PDT agents over the past decade. Many elegant strategies have been developed to enhance the singlet oxygen generation efficiency and the cancer/tumor cell selectivity of BODIPY-based photosensitizers to improve the therapeutic outcomes as well as to minimize the side effects. Many of the currently reported BODIPY-based photosensitizers are valuable dual imaging and therapeutic agents, which can efficiently generate singlet oxygen for PDT and emit fluorescence for in vivo imaging. Although the currently approved PDT agents used for clinical trials do not feature BODIPYs, this situation is expected to change. In this review, we provide an overview of the various strategies that have been used to improve the singlet oxygen generation efficiency for tuning BODIPY fluorophores into photosensitizers and dual imaging/therapeutic agents. Their photophysical properties and photocytotoxic activity including the absorption/emission wavelengths, the singlet oxygen generation efficiency (${\mathrm{\Phi }}_{\mathrm{\Delta }})$ and the half maximal inhibitory concentration $({\mathrm{\text{IC}}}_{50})$ of these currently reported photosensitizers are summarized. We believe these newly developed BODIPY-based photosensitizers will broaden current concepts of strategies for PDT agent design, and promise to make an important contribution to the diagnosis and therapeutics for the treatment of cancer.

A large diversity of porphyrin–diketopyrrolopyrrole conjugates and related structures formed by diketopyrrolopyrrole units and pyrrole-based moieties such as phthalocyanine, porphycene, calix[4]pyrrole or BODIPY have been reported since 2010. The new compounds, whether small molecules or polymeric materials, exhibit very interesting photophysical properties and have been tested in a range of technical or biological applications. This review summarizes the advances in the synthesis of such compounds. Their photophysical properties and potential applications are also briefly discussed.

A near-infrared absorbing boron-dipyrromethene (BODIPY) chromophore coupled with two benzoquinone moieties at its 3,5-positions, 3, was prepared via Knoevenagel condensation of 1,3,5,7-tetramethyl-8-(4${}^{\prime }$-benzonitrile) BODIPY 1 with 3,5-di-tert-butyl-4-hydroxybenzaldehyde to afford 1,7-dimethyl-3,5-di-(4${}^{\prime }$-hydroxy-3${}^{\prime }$,5${}^{\prime }$-di-tert-butyl styryl)-8-(4${}^{\prime }$-benzonitrile) BODIPY 2, followed by oxidization with Ag₂O in good yield (91%). The UV-vis-NIR absorption spectrum of 3 exhibits two major bands at 795 and 895 nm in the near-IR region, while 2shows maximum absorbance at 661 nm and strong fluorescence at 692 nm (${\mathrm{\Phi }}_F=$ 0.59). The cyclic voltammetry of 3 consists of two pairs of reversible one-electron reductions at -0.61 V and -0.88 V and two pairs of one-electron oxidation waves at 0.26 V and 0.54 V. Compared with the redox potentials of 2($E_{1/2{\mathrm{\text{red}}}_1}=-1.32$ V and $E_{1/2\mathrm{\text{ox1}}}=$ 0.25 V), the first reduction of 3 is anodically shifted for 710 mV, whereas the first oxidation potential is close. Theoretical calculation reveals that conjugation with the benzoquinone moieties on the BODIPY chromophore significantly lowers the LUMO energy level and the HOMO–LUMO energy gap, resulting in a dramatic bathochromic shift of the S₀–S₁ transition of 3 compared with that of 2. X-ray crystallographic analysis of 3 reveals that the whole molecule adopts a V-type twisted conformation along the delocalized $\pi$-conjugated pathway.

3,/3,5-Dithienosilole-vinyl-BODIPYs were readily synthesized through Knoevenagel condensation reactions. Spectroscopic properties of two dyes in various solvents were investigated. Dyes 1 and 2 show an absorption maxima at 620 and 738 nm with absorption coefficient of 60900 and 77900 ${\text{M}}^{-1}·$ cm${}^{-1}$ in DCM, respectively. Significant red shifts of the main spectral bands are observed relative to that of the parent 1,3,5,7-tetramethyl-BODIPY. TD-DFT calculations reproduce the spectral shifts and experimental spectra.

A series of meso-(2-benzimidazolyl)-substituted boron dipyrromethene (BODIPY) derivatives 3a–3c and 4 have been synthesized and characterized. The absorption and fluorescence bands of 3a are bathochromically shifted by 36 nm and 61 nm, respectively, compared with those of the meso-phenyl BODIPY in toluene. More importantly, the fluorescence quantum yields of these meso-(2-benzimidazolyl)-substituted BODIPYs (up to 0.45 in toluene) are much higher than those of the previously reported meso-heterocyclic BODIPYs. X-ray crystallographic analysis of the single crystal structure of 3a revealed that the dihedral angle of meso-benzimidazolyl ring and indacene plane (40.47${}^{\circ }$ ) is smaller compared with that of the meso-tolyl substituted BODIPY (61.4${}^{\circ }$ ). Replacement of the six-membered ring with a five-membered ring, as well as the absence of hydrogen at the imino-nitrogen, generated the reduced repulsion and the hydrogen bonding interaction. The increased planarity not only provided the substantial delocalization of $\pi$ electrons and red shifted the absorption and emission bands but also enhanced the fluorescence quantum yield by reducing free rotation induced nonradiative deactivation pathway. Furthermore, 3,5-distyryl coupled BODIPY 4 exhibits a NIR fluorescence band at 712 nm with moderate quantum yield (${\mathrm{\Phi }}_{\mathrm{\text{F}}}$$>$ 0.3) in nonpolar and polar solvents, which indicate that meso-(2-benzimidazolyl) BODIPY acts as a good candidate for post modification toward NIR dyes for biological applications.

A novel asymmetrical zinc(II) phthalocyanine-BODIPY conjugate (ZnPc-BODIPY) bearing three iodine groups directly substituted to the macrocycle and one BODIPY connected to the macrocycle with an amide bond was synthesized by the reaction of carboxylic-acid-substituted asymmetrical zinc(II) phthalocyanine (ZnPc) with the BODIPY-derivative-bearing amino group (BODIPY-NH₂). This conjugate was fully characterized by spectroscopic methods (FT-IR, UV-vis, ¹H NMR, ¹¹B NMR, ¹⁹F NMR and mass) and elemental analysis. The fluorescence behavior of ZnPc-BODIPY was studied to determine the energy transfer process. Voltammetry measurements (CV and SWV) were performed to specify the HOMO–LUMO energy levels and band gaps of ZnPc-BODIPY and starting compounds (ZnPc and BODIPY-NH₂) for comparison. In addition, the band gaps of these compounds were also determined by UV-vis absorption onset (λ_onset) and theoretical calculations. Bulk heterojunction solar cells containing ZnPc-BODIPY were fabricated in the structure of ITO/PEDOT:PSS/ZnPc-BODIPY:PCBM/Al. The photovoltaic parameters of the solar cell were obtained and the ZnPc-BODIPY conjugate was found to bring spectral contribution to IPCE at a peak of 510 nm.

Three BODIPYs bearing 1,3,5,7-tetramethyl substituents and a meso-8-aryl group were synthesized and investigated, both experimentally and computationally. The presence of the 1,7-methyl groups and of ortho-substituents on the meso-8-aryl ring prevent free rotation of the meso-8-aryl group, resulting in high fluorescence quantum yields. Substitution at the 2,6-positions of these BODIPYs with chlorine atoms causes pronounced red-shifted absorptions and emissions, and in the case of 2,6-dichloro-1,3,5,7-tetramethyl-8-(2,4,6-triphenylphenyl)-BODIPY 2c increases its fluorescence quantum yields to 0.93 in dichloromethane and 0.98 in toluene. The X-ray structure of 1,3,5,7-tetramethyl-8-(2,4,6-triphenylphenyl)-BODIPY shows increased deviation from planarity and smaller dihedral angle of the meso-8-aryl group compared with the meso-8-phenyl- and meso-8-mesityl-BODIPY analogs. The presence of 2,6-chlorine atoms was found to not significantly affect the rotational barriers of the meso-8-aryl-groups.

Three new covalently linked BODIPY-metal dipyrrin conjugates (Pd${}^{2+}$, Zn${}^{2+}$ and Re${}^{1+})$ were synthesized by treating $\beta$-dipyrrinyl BODIPY with appropriate metal salts in toluene in the presence of triethylamine at 120$deg$ C. The conjugates were isolated in decent yields either by recrystallization or by column chromatographic purification. The conjugates were thoroughly characterized by 1D and 2D NMR spectroscopy, absorption, cyclic voltammetry and DFT/TD-DFT studies. The studies revealed that the BODIPY and metal dipyrrin moieties in conjugates interact very weakly with each other and retain their individual characteristic features. The conjugates are electron deficient and non-fluorescent in nature.

We report a series of alkyne-functionalized meso-aryl boron dipyrrin (BODIPY) molecular rotors sensitive to viscosity. The planar and twisted conformation within the molecular structure decides the viscosity-dependent behavior. The variations in fluorescence lifetime and intensity were appreciable to the local viscosity. Hence, the dye has been successfully employed in the enumeration of microbes by considering the proportionate fluorescence intensity of the BODIPYs as an index of the number of cells per mL. With increasing cells per mL, the viscosity of the bacterial solution is increased. Consequently, the fluorescence intensity of the sample containing BODIPY tends to increase due to the restricted rotation in the viscous medium. The BODIPY probe offers high sensitivity and is easier than other conventional techniques of colony-forming unit (CFU) determination. The theoretical studies indicate that intramolecular charge transfer is responsible for the enhanced fluorescence intensity in a highly viscous solvent.