Volume of activation for the radiationless deactivation of singlet oxygen in aromatic hydrocarbons

Abstract

Phosphorescence lifetimes of singlet oxygen ('02; I A,) were measured in six aromatic hydrocarbons at pressures of up to 400 MPa. The lifetimes decreased significantly with increasing pressure in the solvents examined. The observed activation volumes, AVD*, for the quenching by solvent were in the range from -8.3 cm3/mol (benzene) to-20.1 cm3/mol (mesitylene), and they decreased with decreasing ionization potential of solvents. The activation volumes for the quenching by solvent in alkane and acetonitrile were nearly equal to the volume changes for encounter+omplex formation estimated by using a hard-sphere model, A V I (~~) , while the discrepancy between AVD* and AV,(HS) in aromatic hydrocarbons increased with decreasing the ionization potential of the solvents.The enhanced decrease of AVD* in aromatic hydrocarbons was interpreted by assuming the formation of exciplexes between '02 and the solvent. The effect of the ionization potential of the solvent on the magnitude of the values for AVD* is discussed.

A Hand‐held Fiber‐optic Implement for the Site‐specific Delivery of Photosensitizer and Singlet Oxygen

“…Changing the solvent from toluene‐ h 8 to toluene‐ d 8 led to an 8‐fold increase of the photocleavage yield of 3 , which was similar to the 9.7‐fold 1 O 2 lifetime increase [cf. τ Δ = 264 μs (toluene‐ d 8 ) to τ Δ = 30 μs (toluene‐ h 8 )] (26,45,46). Alkene bonds of the ( Z )‐1,2‐dialkoxyethene (47–49) and disulfidoethene types (50,51) are chemically reactive with 1 O 2 with total rate constants of ca 4 × 10 7 m −1 s −1 (43,52).…”

“…Changing the solvent from toluene-h 8 to toluene-d 8 led to an 8-fold increase of the photocleavage yield of 3, which was similar to the 9.7-fold 1 O 2 lifetime increase [cf. s D = 264 ls (toluene-d 8 ) to s D = 30 ls (toluene-h 8 )](26,45,46). Alkene…”

Synthesis of the Dimethyl Ester of 2'‐Cyano‐8'‐formyl‐N'‐methyl‐1',1a',5a',6'‐tetrahydroacrido[4,5,5a,6‐bcd]‐Annulated 2,3‐Dihydromesoporphyrin – A Novel System with Outstanding Properties as Basis for Photodynamic Therapy in the Far‐Red Region of the Visible Spectrum

“…The crude product was purified by silica gel chromatography using a mixture of 1 % of methanol in dichloromethane as the eluent. The product was recrystallized from a mixture of dichloromethane and hexanes giving a yield of 29 mg (0.04 mmol, 62 % 4 -H], 7.59 (br., 1 H, 2 2 -H), 9.04 (s, 1 H, 20-CH), 9.14 (s, 2 3Ј -CHO), 9.40 (s, 1 H, 2 10 -CH), 9.53 (s, 1 H, 10-CH), 9.57 (s, 1 H, 15-CH) ppm. 13 C NMR (150.9 MHz): δ = 9.9 (CH 3 -3 2Ј ), 11.3 (CH 3 -18 1 ), 11.5 (CH 3 -12 1 ), 15.5 (CH 3 -7 1 ), 17.2 (CH 3 -8 2 ), 19.3 (CH 2 -8 1 ), 21.4 (CH 2 -17 1 ), 21.6 (CH 2 -13 1 ), 22.5 (CH 3 -2 1Ј ), 27.7 (CH 3 -3 1Ј ), 36.4 (CH 2 -17 2 ), 36.8 (CH 2 -13 2 ), 37.5 (NCH 3 -2 7Ј ), 51.7 (OCH 3 -13 5 ), 51.8 (OCH 3 Reaction of 1 with (Chloromethylene)dimethylammonium Dichlorophosphate: POCl 3 (0.40 mL, 4.3 mmol) was added dropwise to an ice-cold mixture of dimethylformamide (0.55 mL, 4.5 mmol) and 1.0 mL of chloroform, after which the mixture was stirred at room temperature for 20 min.…”

“…Peaks are also present at 1676 cm -1 and a Fermi doublet at 2730 and 2802 cm -1 , indicating that there is an aldehyde group attached to an electron-rich part of the molecule. HR-ESI mass spectrometry gave an exact mass of m/z = 847.3133, which corresponds with an elemental composition of 12 4 with an unsaturation number of 21. This means that 5 contains nine more carbon atoms, seven more hydrogen atoms, one more nitrogen and one more oxygen atom than 5-(2 Ј -cyanovinyl)mesoporphyrin dimethyl ester.…”

“…Typical decay times were 28 ± 1 µs, which is characteristic for singlet oxygen decay in toluene. [4] Tetraphenylporphyrin was used as a standard to determine the relative singlet oxygen yield (Φ ∆ ). [5] The relative singlet oxygen quantum yield for 5 in air-saturated toluene was 0.72 which is close to the singlet oxygen quantum yield for the nickel-free form of 2 (Φ ∆ = 0.77).…”