Kinetic Study of the Photoexcited Triplet State of Free Base Porphyrins by EPR

Scherz, Avigdor; Orbach, N.; Levanon, Haim

doi:10.1002/ijch.197400099

Cited by 7 publications

(1 citation statement)

References 19 publications

(15 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…66 Overlaid in red is a simulation of the triplet using the zfs parameters: |D| = 1294 MHz and E/D = 0.118, which falls within the range expected for a free-base porphyrin. 67,68 The spectrum of 3 exhibits the same polarization and has largely the same spectral shape as 2 with the exception of a small negative peak at 338 mT. This negative peak can be attributed to some nonzero coupling between the TEMPO radical and the triplet; 69,70 however, the small amplitude and lack of other spectral changes make simulating the spectrum underdetermined.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

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

et al. 2020

View full text Add to dashboard Cite

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.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 93%