PDT-related photophysical properties of conformationally distorted palladium(II) porphyrins

2001 ◽  
Vol 05 (12) ◽  
pp. 853-860 ◽  
Author(s):  
A. WIEHE ◽  
H. STOLLBERG ◽  
S. RUNGE ◽  
A. PAUL ◽  
M. O. SENGE ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Molecular Oxygen ◽  
Photophysical Properties ◽  
Bathochromic Shift ◽  
Luminescence Spectroscopy ◽  
Quantum Yields ◽  
Triplet States ◽  
Singlet Molecular Oxygen ◽  
Time Resolved ◽  
Phosphorescence Quantum Yield

The photodynamic therapy (PDT) related photophysical properties of five palladium(II) porphyrins with increasing steric demand of the meso-substituents were investigated by steady state and time-resolved absorption and luminescence spectroscopy. The steric strain of the meso-substituents is reflected in a bathochromic shift of the B-band in the absorption spectra. In contrast to free-base porphyrins, the palladium(II) complexes exhibit only a very weak fluorescence with Φ Fl ~ 10-4. Instead, the corresponding triplet states of the porphyrins are formed via inter system crossing (ISC) with a quantum yield ΦISC of nearly unity. A phosphorescence quantum yield ΦISC of 10-4 was determined assuming dynamic quenching. The triplet state of all compounds is efficiently quenched by molecular oxygen, generating singlet molecular oxygen with a quantum yield of ΦΔ ~ 0.85. The various substitution patterns exerted no significant influence on the ISC rates or singlet oxygen quantum yields. Significant differences, on the other hand, were observed with respect to the triplet lifetimes, with a tendency of longer lifetimes for the porphyrins with sterically more demanding substituents (in air-saturated solution). All porphyrins were successfully incorporated into liposomes. The phototoxic activity of three compounds was investigated in cell suspensions. The use of the new porphyrinato-palladium(II) in PDT applications is discussed.

Determination of the phosphorescence quantum yield of singlet molecular oxygen (1Δg) in benzene

1987 ◽  
Vol 138 (1) ◽  
pp. 18-22 ◽  
Author(s):  
R. Schmidt ◽  
H.-D. Brauer ◽  
K.H. Drexhage
Keyword(s):  
Quantum Yield ◽  
Molecular Oxygen ◽  
Singlet Molecular Oxygen ◽  
Phosphorescence Quantum Yield

Host-guest complexes of anionic porphyrin sensitizers with cyclodextrins

2002 ◽  
Vol 06 (08) ◽  
pp. 514-526 ◽  
Author(s):  
Jiří Mosinger ◽  
Viktor Kliment ◽  
Jan Sejbal ◽  
Pavel Kubát ◽  
Kamil Lang
Keyword(s):  
Singlet Oxygen ◽  
Specific Binding ◽  
Photophysical Properties ◽  
Bathochromic Shift ◽  
Fluorescence Emission ◽  
Binding Constants ◽  
Quantum Yields ◽  
Hydroxyl Groups ◽  
Triplet States ◽  
Binding Modes

The photodynamic sensitizers zinc(II)- and palladium(II)-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrins and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin form 1:1 and/or 1:2 supramolecular complexes with native cyclodextrins (CD) and 2-hydroxypropyl cyclodextrins (hpCD) in aqueous neutral solutions. The formation of these assemblies causes a bathochromic shift of the porphyrin Soret band in the UV-vis spectra and a red shift of the fluorescence emission bands. The binding constants span over three orders of magnitude, from 8.1 × 102 M −1 to 5.4 × 105 M −1 (or 1.1 × 106 M −2) depending on the size of the CD cavity and on the functionalization by adding 2-hydroxypropyl groups. The highest binding constants were obtained for hpβCD and hpγCD. The Nuclear Overhauser spectroscopy signals (ROESY) revealed three binding modes: i) inclusion of the porphyrin 4-sulfonatophenyl or 4-carboxyphenyl groups via the secondary face of βCD and hpβCD with sulfonic or carboxylic groups oriented towards the primary hydroxyl groups. ii) inclusion of the porphyrin groups via the primary face of γCD and hpγCD. iii) non-specific binding of the porphyrin monomers or aggregates on the cyclodextrin exterior. The inclusion host-guest complexation via i) or ii) does not influence the inherent photophysical properties of the monomeric porphyrins such as the quantum yields of fluorescence, the triplet states, and the singlet oxygen formation. Due to the deaggregation effect of cyclodextrins, the inclusion complexes remain efficient supramolecular sensitizers of singlet oxygen even under conditions of extensive aggregation in aqueous solutions.

Determination of the phosphorescence quantum yield of singlet molecular oxygen (1.DELTA.g) in five different solvents

1989 ◽  
Vol 93 (11) ◽  
pp. 4507-4511 ◽  
Author(s):  
R. Schmidt ◽  
K. Seikel ◽  
H. D. Brauer
Keyword(s):  
Quantum Yield ◽  
Molecular Oxygen ◽  
Singlet Molecular Oxygen ◽  
Phosphorescence Quantum Yield

The photolysis of ozone by ultraviolet radiation. IV. Effect of photolysis wavelength on primary step

1970 ◽  
Vol 319 (1537) ◽  
pp. 273-287 ◽  
Keyword(s):  
Quantum Yield ◽  
Ultraviolet Radiation ◽  
Molecular Oxygen ◽  
Ozone Concentration ◽  
Pressure Range ◽  
Quantum Yields ◽  
Ultraviolet Region ◽  
Singlet Molecular Oxygen ◽  
Weak Absorption ◽  
Absorption Tail

Quantum yields for the photolysis of ozone have been measured at six wavelengths in the region 248 to 334 nm. The quantum yield for the photolysis of pure ozone increases linearly with ozone concentration over the pressure range employed for λ ≤ 310 nm, but is virtually independent of [O 3 ] at λ = 334 nm. At all wavelengths the quantum yield, extrapolated to zero ozone pressure, is near 4. Addition of H 2 to the ozone markedly increases the quantum yield at all wavelengths except λ = 334 nm. Dilution of the ozone by O 2 reduces the quantum yield; at high [O 2 ] the quantum yield tends to zero. It is shown that the results are consistent with the production of singlet molecular oxygen (in the 1 ∆ g or 1 ∑ + g states) in the primary step at all wavelengths in the ultraviolet region. For λ ≤ 302 nm the atomic product is in the excited, 1 D, state, O 3 + hv (λ ≤ 302nm) → O 2 ( 1 ∑ + g or 1 ∆ g ) + O( 1 D), but with increasing wavelength the efficiency of O( 1 D) production drops rapidly, and at λ = 334 nm the atomic product is almost exclusively O( 3 P). O 3 + hv (λ = 334 nm) → O 2 ( 1 ∑ g + or 1 ∆ g ) + O( 3 P). Thus it appears that ozone photolysis in the weak absorption tail of the Huggins band does not proceed with conservation of spin. Some possible implications of the laboratory observations in atmospheric photochemistry are considered.

Photophysics of novel 22π porphyrinoids

2012 ◽  
Vol 16 (05n06) ◽  
pp. 499-507 ◽  
Author(s):  
Daniel O. Mártire ◽  
Sigrid Russell ◽  
Hans-Jürgen Dietrich ◽  
Carlos J. Cobos ◽  
Silvia E. Braslavsky
Keyword(s):  
Triplet State ◽  
Molecular Oxygen ◽  
Photophysical Properties ◽  
Intersystem Crossing ◽  
Quenching Rate ◽  
Triplet Energy ◽  
Singlet Molecular Oxygen ◽  
Time Resolved ◽  
Quenching Rate Constant ◽  
New Compounds

The photophysical properties of toluene solutions of two new 22π expanded porphycene compounds were measured using a combination of various steady-state and time-resolved techniques. The determined triplet energy (E T = 109 ± 3) kJ.mol-1, coincident with the calculated E T = (96.0 ± 10) kJ.mol-1, of both red absorbing compounds is higher than the energy required to excite ground state molecular oxygen to singlet molecular oxygen. However, the intersystem crossing yield is very low (ca. 10-2), which makes these compounds poor photosensitizers. The triplet state yield of the two expanded 22π porphyrinoid compounds is much lower than that of the parent porphycene, whereas their fluorescence is as high (ca. 30%) as the value for porphycene. The slower than diffusional quenching rate constant of a porphycene triplet state by the two new compounds reflects a steric hindering factor of the exothermic energy transfer.

Environmental photodegradation of pyrimidine fungicides — Kinetics of the visible-light-promoted interactions between riboflavin and 2-amino-4-hydroxy-6-methylpyrimidine

2002 ◽  
Vol 80 (1) ◽  
pp. 62-67 ◽  
Author(s):  
E Haggi ◽  
S Bertolotti ◽  
S Miskoski ◽  
F Amat-Guerri ◽  
N A García
Keyword(s):  
Visible Light ◽  
Molecular Oxygen ◽  
Superoxide Anion ◽  
Flash Photolysis ◽  
Triplet States ◽  
Excited Singlet ◽  
Singlet Molecular Oxygen ◽  
Time Resolved ◽  
Singlet And Triplet States ◽  
Kinetics Of

To clarify the evolution of pyrimidine fungicides under natural aquatic environmental conditions, the visible-light-promoted degradation of the model fungicide 2-amino-4-hydroxy-6-methylpyrimidine (AHMPD) has been studied in air-equilibrated pH 6 aqueous solutions in the presence of riboflavin (Rf), employing time-resolved and stationary kinetic–spectroscopic methods. AHMPD, a compound practically inert towards the attack of singlet molecular oxygen (O2(1Δg)), quenches excited singlet and triplet states of Rf with rate constants of 2.7 × 109 M–1 s–1 and 2.7 × 107 M–1 s–1, respectively. In the presence of AHMPD, the photodecomposition of Rf, which occurs from the excited triplet state of the pigment, depends on the concentration of the fungicide: at [Formula: see text]40–50 mM a limited photochemistry occurs due to the quenching of excited singlet Rf, while at ca. 5–10 mM triplet Rf is largely photogenerated and subsequently quenched either by oxygen, giving rise to O2(1Δg), or by AHMPD, yielding semireduced Rf through an electron transfer process. Flash photolysis experiments and indirect auxiliary tests confirm the presence of superoxide anion generated by the reaction of Rf anion radical with the dissolved oxygen. The neat result of this intricate scheme of competitive reactions is the photodegradation of both AHMPD and Rf, mainly through a superoxide anion-mediated oxidation, although some contribution of O2(1Δg)-mediated photooxidations cannot be disregarded.Key words: photooxidation, pyrimidine derivatives, riboflavin, singlet molecular oxygen, superoxide anion.

Porphyrin-Sensitized Generation of Singlet Molecular Oxygen: Comparison of Steady-State and Time-Resolved Methods

1995 ◽  
Vol 99 (24) ◽  
pp. 9825-9830 ◽  
Author(s):  
Charles Tanielian ◽  
Christian Wolff
Keyword(s):  
Steady State ◽  
Molecular Oxygen ◽  
Singlet Molecular Oxygen ◽  
Time Resolved
Sign in / Sign up

Export Citation Format

Share Document