scholarly journals Time-Resolved Thermodynamics of Inter-Molecular Electron Transfer Between Water-Soluble Anionic Free-Base Porphyrins and Ubiquinone

2010 ◽  
Vol 98 (3) ◽  
pp. 565a
Author(s):  
William A. Maza ◽  
Randy W. Larsen
Keyword(s):  
Electron Transfer ◽  
Water Soluble ◽  
Free Base ◽  
Time Resolved ◽  
Molecular Electron

Using Quenching Kinetics and Thermodynamics of Amino-Fluorophores as Empirical Tools for Predicting Boronic Acid Sensors Suitable for Use in Physiological Conditions

2011 ◽  
Vol 64 (11) ◽  
pp. 1438 ◽  
Author(s):  
Nicholas McGregor ◽  
Christophe Pardin ◽  
W. G. Skene
Keyword(s):  
Electron Transfer ◽  
Fluorescence Quenching ◽  
Boronic Acid ◽  
Sulfonic Acid ◽  
Phenylboronic Acid ◽  
Water Soluble ◽  
Time Resolved ◽  
Diffusion Limited ◽  
Phenylboronic Acids ◽  
Acid Sensors

A series of water-soluble 1-amino-naphthalenes and 2-amino-fluorenes are prepared. These serve as model fluorophores for measuring the thermodynamics and kinetics of fluorescence quenching with phenylboronic acids and aliphatic amines. Steady-state and time-resolved fluorescence quenching kinetics are investigated using the Stern–Volmer method. Diffusion limited quenching constants and exergonic thermodynamics of electron transfer are derived for the 5-amino-1-napthol and 2-aminofluorene derivatives with phenylboronic acid and/or an aliphatic imine. No quenching and endergonic thermodynamics or electron transfer are observed for 5-sulfonamide, 5-sulfonic acid, or 5-hydroxy-7-sulfonic acid aminonaphthalene derivatives. Boronic acid sensors synthesized from these aminofluorophores by reductive amination with 2-formylphenylboronic acid undergo fluorescence revival in the presence of saccharides only when the fluorophore demonstrates diffusion limited quenching kinetics and exergonic thermodynamics of electron transfer with the boronic acid or imine quenchers. Thus, these two properties are suitable empirical tools for predicting saccharide-induced fluorescence revival of boronic acid sensors.

Synthesis and Photophysical Properties of a Conformationally Flexible Mixed Porphyrin Star-Pentamer

2009 ◽  
Vol 62 (7) ◽  
pp. 692 ◽  
Author(s):  
Toby D. M. Bell ◽  
Sheshanath V. Bhosale ◽  
Kenneth P. Ghiggino ◽  
Steven J. Langford ◽  
Clint P. Woodward
Keyword(s):  
Energy Transfer ◽  
Photophysical Properties ◽  
Fluorescence Decay ◽  
High Yield ◽  
Free Base ◽  
Time Resolved ◽  
Zinc Porphyrin ◽  
Relative Contribution ◽  
Synthetic Strategy ◽  
Decay Times

The synthesis of a porphyrin star-pentamer bearing a free-base porphyrin core and four zinc(ii) metalloporphyrins, which are tethered by a conformationally flexible linker about the central porphyrin’s antipody, is described. The synthetic strategy is highlighted by the use of olefin cross metathesis to link the five chromophores together in a directed fashion in high yield. Photoexcitation into the Soret absorption band of the zinc porphyrin chromophores at 425 nm leads to a substantial enhancement of central free-base porphyrin fluorescence, indicating energy transfer from the photoexcited zinc porphyrin (outer periphery) to central free-base porphyrin. Time-resolved fluorescence decay profiles required three exponential decay components for satisfactory fitting. These are attributed to emission from the central free-base porphyrin and to two different rates of energy transfer from the zinc porphyrins to the free-base porphyrin. The faster of these decay components equates to an energy-transfer rate constant of 3.7 × 109 s–1 and an efficiency of 83%, whereas the other is essentially unquenched with respect to reported values for zinc porphyrin fluorescence decay times. The relative contribution of these two components to the initial fluorescence decay is ~3:2, similar to the 5:4 ratio of cis and trans geometric isomers present in the pentamer.

scholarly journals Inter- and intra-molecular electron transfer in the cytochrome bc1 complex

2002 ◽  
Vol 1555 (1-3) ◽  
pp. 65-70 ◽  
Author(s):  
Chang-An Yu ◽  
Xiaolin Wen ◽  
Kunhong Xiao ◽  
Di Xia ◽  
Linda Yu
Keyword(s):  
Electron Transfer ◽  
Cytochrome Bc1 ◽  
Bc1 Complex ◽  
Cytochrome Bc1 Complex ◽  
Molecular Electron

scholarly journals Photoinduced electron transfer processes of single-wall carbon nanotube (SWCNT)–based hybrids

Nanophotonics ◽  
2020 ◽  
Vol 9 (16) ◽  
pp. 4689-4701
Author(s):  
Lili Du ◽  
Wenjuan Xiong ◽  
Wai Kin Chan ◽  
David Lee Phillips
Keyword(s):  
Electron Transfer ◽  
Transient Absorption ◽  
Electronic Materials ◽  
Photophysical Properties ◽  
Functional Materials ◽  
Single Wall Carbon Nanotubes ◽  
Spectroscopic Techniques ◽  
Time Resolved ◽  
Single Wall Carbon ◽  
Electron Transfer Processes

AbstractIn this review, noncovalent functionalization of single-wall carbon nanotubes (SWCNTs) is briefly reviewed. The functional materials summarized here include metalloporphyrin derivatives, biomolecules and conjugated polymers. Notably, time-resolved spectroscopic techniques such as time-resolved fluorescence and transient absorption were employed to directly investigate the electron transfer and recombination processes between the functionalities and the SWCNTs. In addition, Raman spectroscopy is also useful to identify the interaction and the electron transfer direction between both the functionalities and the SWCNTs. An improved understanding of the mechanisms of these SWCNT-based nanohybrids in terms of their structural and photophysical properties can provide more insights into the design of new electronic materials.

scholarly journals Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

2013 ◽  
Vol 9 ◽  
pp. 1448-1454
Author(s):  
Martin Goez ◽  
Martin Vogtherr
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Nuclear Polarization ◽  
Activation Barrier ◽  
Activation Parameters ◽  
Radical Cations ◽  
Free Energies ◽  
Time Resolved ◽  
Diethyl Sulfide ◽  
Chemically Induced

Electron transfer between the title compounds and their radical cations, which were generated by photoinduced electron transfer from the sulfides to excited 2,4,6-triphenylpyrylium cations, was investigated by time-resolved measurements of chemically induced dynamic nuclear polarization (CIDNP) in acetonitrile. The strongly negative activation entropies provide evidence for an associative–dissociative electron exchange involving dimeric radical cations. Despite this mechanistic complication, the free energies of activation were found to be well reproduced by the Marcus theory of electron transfer, with the activation barrier still dominated by solvent reorganization.

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