Electrochemical Behavior of <i>meso</i>-Substituted Porphyrins: The Role of Cation Radicals to the Half-Wave Oxidation Potential Splitting

Tran, Thai Thi Ha; Chang, Yan-Ru; Hoang, Tuan K.A.; Kuo, Ming‐Yu; Su, Yuhlong Oliver

doi:10.1021/acs.jpca.6b03538

Cited by 20 publications

(10 citation statements)

References 18 publications

(67 reference statements)

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“…However, the zero-field splitting (zfs) between the two unpaired electrons of Ni renders the metal EPR silent at the X band (9.5 GHz), 19,60 and again, we only observe the TEMPO radical. The spectrum of 3(Cu) show an additional multiplet at a lower field because of hyperfine coupling of the copper unpaired electron with the four porphyrin 14 N nuclei, which is characteristic of copper porphyrins. 61,62 Time-Resolved Spectroscopy.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…13 Porphyrins can also exist as stabile oxidized, reduced, or neutral radicals. 14 From a biological perspective, extensive research on oxophlorin and mesohydroxyporphyrin has been carried out to elucidate their role in the catabolism of heme. 15 Inspired by Nature, impressive synthetic achievements have been made in the design and realization of stable porphyrin oxyl radicals with relevant magnetic properties.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Porphyrins represent a class of aromatic, light-harvesting chromophores that can coordinate metals, transforming them to organometallic species with further unique chemical and physical properties . Porphyrins can also exist as stabile oxidized, reduced, or neutral radicals . From a biological perspective, extensive research on oxophlorin and meso -hydroxyporphyrin has been carried out to elucidate their role in the catabolism of heme .…”

Section: Introductionmentioning

confidence: 99%

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Metalated Porphyrin Stable Free Radicals: Exploration of Electron Spin Communication and Dynamics

et al. 2020

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Solvents for chromatography including technical grade ethyl acetate, hexane and dichloromethane were distilled prior to use with a rotary evaporator. Dichloromethane (DCM) used for the porphyrin condensation was purified through SPS system. Methanol for the recrystallization were HPLC grade. Chloroform-d and pyrrole were purified directly before using by passing through a basic alumina column. Trifluoroacetic acid (TFA), 2,3,4,5,6pentafluorobenzaldehyde, 4-cyanobenzaldehyde, 4-Amino-2,2,6,6-tetramethylpiperidinyloxy free radical, propionic acid DIBAL-H (1M solution in DCM) and 2,3-dichloro-5,6-dicyano-1,4benzoquinone (DDQ) were used without further purification. Thin Layer Chromatography was performed on silica, or Al2O3 TLC plates and visualized by illumination with an UV lamp (254 nm and 365 nm wavelength). Silica gel (0.04-0.063 mm) was used as received. Al2O3 was used as received or deactivated with addition of water (3 mL for 100 g of Al2O3 for GII and 6 mL for 100 g of Al2O3 for GIII respectively) and shaking until warming ceased. Size exclusion chromatography was performed on Bio-Beads™ S-X3 Resin with toluene as an eluent. All NMR spectra were recorded at 298 K on 400 MHz, 600 MHz and 700 MHz Bruker Avance III spectrometers. 1 H and 13 C shifts were referenced to the residual solvent signal. The 19 F signals were measured in the presence of an inset with TFA as the external reference. All assignments were obtained with a combination of 2D experiments (COSY, NOESY, HSQC and HMBC ( 13 C and 19 F). Mass spectrometry measurements were recorded on a maXis 4G-UHR-TOF Bruker Daltonics spectrometer using the electrospray technique. UV/Vis spectra were recorded at room temperature using a Perkin-Elmer Lambda 9 spectrophotometers. Continuous wave (CW) EPRLow temperature EPR measurements were performed on ~150 μM solutions of TEMPO radical porphyrins in 2-methyltetrahydrofuran (mTHF). The solutions were contained in quartz tubes with 2.40 mm o.d. and 2.00 mm i.d., subjected to three freeze-pump-thaw cycles on a vacuum line (10 -4 Torr), and flame sealed with a hydrogen torch. EPR measurements were performed at X-band (~9.5 GHz) fields using a Bruker Elexsys E680-X/W spectrometer equipped with a split-ring resonator (ER4118X-MS3), or Bruker ESP300E X-Band, operating at a microwave frequency of 9.85GHz. Temperature was controlled using an Oxford Instruments CF935 continuous flow cryostat. All EPR measurements were made at X-band (~9.5 GHz) fields using a Bruker Elexsys E680-X/W spectrometer equipped with a split-ring resonator (ER4118X-MS3). Continuous wave (CW) EPR spectra were measured with 0.1 mT magnetic field modulation at 100 kHz modulation frequency and non-saturating microwave power between 0.1 and 0.15 mW at 85K.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Metalated Porphyrin Stable Free Radicals: Exploration of Electron Spin Communication and Dynamics

et al. 2020

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“…The biological systems present microheterogeneity, caused by the coexistence of microphases such as aqueous polar and highly hydrophobic lipid. 64,65 Therefore it is relevant to study the physicochemical properties of sensitizers at different media. We have studied the electrochemical behavior of (2) using cyclic voltammograms (CV) in four different solvents.…”

Section: Electrochemical Characterizationmentioning

confidence: 99%

Photophysical study and in vitro approach against Leishmania panamensis of dicloro-5,10,15,20-tetrakis(4-bromophenyl)porphyrinato Sn(IV)

et al. 2021

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Background: Photodynamic therapy activity against different biological systems has been reported for porphyrins. Porphyrin modifications through peripheral groups and/or by metal insertion inside the ring are main alternatives for the improvement of its photo-physical properties. In this study, we synthesized and characterized 5,10,15,20-tetrakis(4-bromophenyl)porphyrin and the dicloro-5,10,15,20-tetrakis(4-bromophenyl)porphyrinato Sn(IV). Methods: Metal-free porphyrin was synthesized using the Alder method, while the Sn(IV)-porphyrin complex was prepared by combining metal-free porphyrin with stannous chloride in DMF; the reaction yields were 47% and 64% respectively. Metal-free porphyrin was characterized by UV-Vis, FT-IR, ESI-mass spectrometry and 13C-NMR. Additionally, the Sn(IV) -porphyrin complex was characterized using UV-Vis and FT-IR. Cyclic voltammetry tests in four different solvents. The fluorescence quantum yield (Φf) was measured using fluorescein as a standard, the singlet oxygen quantum yield (ΦD) was estimated using the standard 5,10,15,20-(tetraphenyl)porphyrin (H2TPP) and the quencher of singlet oxygen 1,3-diphenylisobenzofuran (DPBF). Results: UV-Vis assay showed typical Q and Soret bands for porphyrin and its metallo-porphyrin complex. Compounds showed photoluminescence at the visible range of electromagnetic spectrum. The inclusion of the metal in the porphyrin core changed the Φf from 0.15 to 0.05 and the ΦD increased from 0.55 to 0.59. Finally, the effect of the compounds on the viability of L. panamensis was evaluated by means of the MTT test. The results showed that both compounds decreased the viability of the parasite; this inhibitory activity was greater under light irradiation; the porphyrin compound had IC50 of 16.5 μM and the Sn(IV)-porphyrin complex had IC50 of 19.2 μM. Conclusion: The compounds were synthesized efficiently, their characterization was carried out by different spectroscopy techniques and their own signals were evidenced for both structures, both compounds decreased the cell viability of L. panamensis.

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“…We have found that the effect of porphyrin ring deformation on the half-wave oxidation potential splitting (Δ E = second E 1/2 – first E 1/2 ) values of the free base prophyrins is less than the effect of sterically controlled π-conjugation of the meso -phenyl groups to the central porphyrin ring, defined by the dihedral angles (ψ) between meso -phenyl groups and porphyrin ring. Recently, we have published a study on zinc porphyrins with meso -substituted five-membered heterocylic rings . We found that Δ E can be easily predicted by calculating the spin density distribution of zinc porphyrin cation radicals on meso -carbon positions.…”

Section: Introductionmentioning

confidence: 99%

Effect of Imidazole on the Electrochemistry of Zinc Porphyrins: An Electrochemical and Computational Study

et al. 2017

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In this study, the electrochemical behavior of zinc meso-substituted porphyrins in the presence of imidazole is examined by using both cyclic voltammetry (CV) and density functional theory (DFT) methods. The results show that the first half-wave oxidation potentials (1st E) of zinc porphyrins complexed with imidazole all move to the negative side, while the second ones (2nd E) move to the positive side, resulting in larger half-wave oxidation potential splittings of the two oxidation states (ΔE = second E - first E) comparing with the zinc porphyrins. By employing DFT calculations, we have found that both sterically controlled inter π-conjugation between porphyrin rings and meso-substituted phenyl groups and deformation of porphyrin rings do play important roles in contributing to the half-wave oxidation potentials. Imidazole exhibits strong effects on the deformation of porphyrin rings which is dominant in determining the first E while the inter π-conjugation between porphyrin rings and meso-substituted phenyl groups mainly contributes to the second E. Without imidazole, the inter π-conjugation between porphyrin rings and meso-substituted phenyl groups is the only important criterion which effects both first E and second E of zinc porphyrins.

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Electrochemical Behavior of meso-Substituted Porphyrins: The Role of Cation Radicals to the Half-Wave Oxidation Potential Splitting

Cited by 20 publications

References 18 publications

Metalated Porphyrin Stable Free Radicals: Exploration of Electron Spin Communication and Dynamics

Metalated Porphyrin Stable Free Radicals: Exploration of Electron Spin Communication and Dynamics

Photophysical study and in vitro approach against Leishmania panamensis of dicloro-5,10,15,20-tetrakis(4-bromophenyl)porphyrinato Sn(IV)

Effect of Imidazole on the Electrochemistry of Zinc Porphyrins: An Electrochemical and Computational Study

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