Microwave-assisted synthesis, photochemical and electrochemical studies of long-wavelength BODIPY dyes

Novel BODIPY derivatives possessing different styryl substituents were synthesized using different methods of Knoevenagel-type condensation with conventional heating and microwave radiation in two conditions. Microwave-assisted synthesis significantly reduces reaction time while enhancing its efficiency. The introduction of styryl substituents at the 3 and 5 positions of the BODIPY core resulted in a substantial bathochromic shift, which was affected by the substituents within styryl groups. Depending on the solvents, the BODIPY with unsubstituted styryl groups possesses absorption maxima (λAbs) between 616 and 626 nm. While the analogs containing electron-donating methoxy and methylthio groups exhibited bathochromically shifted bands with λAbs values in the 633-654 nm range. Fluorescence studies revealed intensive emission of tested BODIPYs with fluorescence quantum yields at the 0.41-0.83 range. On the other hand, singlet oxygen quantum yields were very low. In the electrochemical studies, the CV and DPV scans showed the presence of three redox processes. The calculated electrochemical gaps were in the range of 1.71-1.87 V.

Photodynamic activity of 2,6-dibrominated dimethylaminophenylbuta-1,3-dienylBODIPY dyes

Mono- and disubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes were successfully prepared, and their in vitro photodynamic activities against MCF-7 breast cancer cells were evaluated with a Thorlabs M660L4 660 nm LED (336 J · cm[Formula: see text]. The IC[Formula: see text] value of the monophenylbuta-1,3-dienylBODIPY was ca. 2.1 [Formula: see text]M, while that of the diphenylbuta-1,3-dienylBODIPY was > 50 [Formula: see text]M. Both dyes exhibited minimal dark toxicity. The results demonstrate that monosubstituted 2,6-dibromo-dimethylaminophenylbuta-1,3-dienylBODIPY dyes merit further in-depth study for use as photosensitizer dyes in photodynamic therapy.

Optical limiting properties of D-π-A BODIPY dyes in the presence and absence of methyl groups at the 1,7-positions

The optical limiting properties of three meso-pentafluorophenylstyrylBODIPY dyes are investigated in the presence and absence of methyl groups at the 1,7-positions that hinder free rotation of the meso-aryl group. Pentafluorophenyl groups are introduced at the meso-position, while 4-diethylaminostyryl groups are introduced at the 3- and/or 5-positions to form dyes with strong donor-[Formula: see text]-acceptor (D-[Formula: see text]-A) properties to enhance the dipole moment of the molecule. Favorable optical limiting properties are obtained for all three dyes, with the highest second-order hyperpolarizability value obtained for a monostyryl dye with no methyl groups at the 1,7-position. Bromination at the 2,6-positions of a 1,7-methyl substituted dye is found to result in second-order hyperpolarizability that is an order of magnitude lower than that calculated for the analogous non-halogenated dye.

Photodynamic activity of 2,6-diiodo-3,5-dithienylvinyleneBODIPYs and their folate-functionalized chitosan-coated Pluronic® F-127 micelles on MCF-7 breast cancer cells

A 2,6-diiodo-3,5-dithienylvinyleneBODIPY dye was prepared and encapsulated with folate-chitosan capped Pluronic[Formula: see text] F-127 to provide drug delivery systems for photodynamic therapy (PDT). Moderately enhanced singlet oxygen quantum yields were observed for the dye encapsulation complexes in water. The in vitro dark cytotoxicity and photodynamic activity were investigated on the human breast adenocarcinoma (MCF-7) cell line. Minimal dark cytotoxicity was observed for the BODIPY dyes in 5% DMSO and when encapsulated in folate-functionalized chitosan-coated Pluronic[Formula: see text] F-127 micelles, since the cell viability values are consistently greater than 80% over the 0-40 [Formula: see text] concentration range. Upon irradiation of the samples, significant cytocidal activity was observed for the encapsulation complex of a 2,6-diiodo-8-dimethylaminophenyl-3,5-dithienylvinyleneBODIPY dye with less than 50% viable cells observed at concentrations [Formula: see text].

Exploring the relationship between structure and activity in BODIPYs designed for antimicrobial phototherapy

A synthetic strategy to BODIPY dyes is presented giving access to a range of new compounds relevant in the context of antimicrobial photodynamic therapy (aPDT). BODIPYs with the 8-(4-fluoro-3-nitrophenyl) and the 8-pentafluorophenyl substituents were used for the synthesis of new mono- and dibrominated BODIPYs. The para-fluorine atoms in these electron-withdrawing groups facilitate functional modification via nucleophilic aromatic substitution (SNAr) with a number of amines and thio-carbohydrates. Subsequently, the antibacterial phototoxic activity of these BODIPYs has been assessed in bacterial assays against the Gram-positive germ S. aureus and also against the Gram-negative germ P. aeruginosa. The bacterial assays allowed to identify substitution patterns which ensured antibacterial activity not only in phosphate-buffered saline (PBS) but also in the presence of serum, hereby more realistically modelling the complex biological environment that is present in clinical applications.

Optical Limiting and Femtosecond Pump-Probe Transient Absorbance Properties of a 3,5-distyrylBODIPY Dye

The optical limiting (OL) properties of a 3,5-di-p-benzyloxystyrylBODIPY dye with an p-acetamidophenyl moiety at the meso-position have been investigated by using the open-aperture Z-scan technique at 532 nm with 10 ns laser pulses. There is a ca. 140 nm red shift of the main spectral band to 644 nm relative to the corresponding BODIPY core dye, due to the incorporation of p-benzyloxystyryl groups at the 3,5-positions. As a result, there is relatively weak absorbance across most of the visible region under ambient light conditions. Analysis of the observed reverse saturable absorbance (RSA) profiles demonstrates that the dye is potentially suitable for use in optical limiting applications as has been reported previously for other 3,5-distyrylBODIPY dyes. Time-resolved transient absorption spectroscopy and kinetic studies with femtosecond and nanosecond scale laser pulses provide the first direct spectral evidence that excited state absorption (ESA) from the S₁ state is responsible for the observed OL properties.

Optical limiting properties of BODIPY dyes substituted with styryl or vinylene groups on the nanosecond timescale

The results of recent studies on the optical limiting properties of BODIPY dyes at 532 and 1064 nm are described and compared. The optical limiting properties of novel 1,7-dimethyl-3,5-di-4-dihydroxyborylstyryl- and 3,5,7-tristyryl-1-methyl-BODIPY dyes were studied in CH2Cl2 and C6H6 and polystyrene thin films using the open aperture Z-scan technique at 532 nm with nanosecond laser pulses to provide an example of how the effective nonlinear absorption coefficient, the third order susceptibility, hyperpolarizability and limiting thresholds can be calculated.

Photophysical properties and photodynamic therapy activities of detonated nanodiamonds-BODIPY-phthalocyanines nanoassemblies

This work reports on the synthesis of nanoassemblies of supramolecular hybrids containing detonated nanodiamonds (DNDs) covalently linked to halogenated BODIPY (DNDs-BODIPY) by an amide bond, followed by π-π stacking of 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) on the DNDs-BODIPY conjugate, to form nanoassembly represented as ZnTPPcQ-DNDs-BODIPY. ZnTPPcQ-DNDs-BODIPY has a higher singlet oxygen quantum yield of 0.50 in water. Therefore, the construction of a three component photodynamic therapy agent (ZnTPPcQ-DNDs-BODIPY) as a single photosentisiser improved singlet quantum yields of the Pc. Zeta potential studies of ZnTPPcQ-DNDs-BODIPY under various temperatures, concentrations and pH conditions, showed the conjugate is more stable at pHs 2, 4 and 7 and at high concentrations (50 μg/mL) and temperatures (80 °C). ZnTPPcQ-DNDs-BODIPY showed high photodynamic therapy (PDT) activity with a low MCF-7 cell viability of 21 ± 5% when compared to 31 ± 2%, 30 ± 2% and 28 ± 2% cell viability at the highest tested concentration of 50 μg/mL for DNDs, ZnTPPcQ-DND and DNDs-BODIPY, respectively.

An analysis of the photophysical and optical limiting properties of a novel 1,3,5-tristyrylBODIPY dye

The synthesis and characterization of a novel dibrominated 1,3,5-tristyrylBODIPY dye is reported, and its potential utility as a singlet oxygen photosensitizer and optical limiting material is assessed. The main spectral band lies in the therapeutic window, and there is a moderately high singlet oxygen quantum yield making the dye potentially suitable for use in biomedical applications and as an optical limiting dye at 532 nm. The optical limiting parameters are comparable to those reported previously for 3,5-distyrylBODIPYs, which suggests that mixtures of 3,5-distyryl and 1,3,5-tristyryl compounds that are formed in Knoevenagel condensation reactions could be used for this application. Theoretical calculations are used to assess the effect of 1,3,5-tristyryl substitution. A smaller red shift of the main spectral band is observed upon styrylation at the 1-position than is the case with the 3,5-positions due to there being smaller MO coefficients at this position, limiting the utility of this structural modification method for shifting the main BODIPY spectral band further into the therapeutic window.