Laser Photo‐Ionization of Phenothiazine in Micellar Solution II: Mechanism and Light Induced Redox Reactions with Quinones

Alkaitis, S. A.; Grätzel, Michaël; Henglein, A.

doi:10.1002/bbpc.19750790613

Cited by 55 publications

(8 citation statements)

References 16 publications

(1 reference statement)

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“…This finding suggests that in medium polar solvents the CT state of dyad 3 is higher in energy than the triplet state of pyrene (2.1 eV) 40 but lower than the triplet state of phenothiazine (2.62 eV). 41 The above estimate is in accord with this conclusion. It provides evidence that the CT state can decay into locally excited triplet states in less polar solvents.…”

Section: Stabilization Of Ct States By Solvent and Geometricalsupporting

confidence: 90%

Phenothiazine−Pyrene Dyads: Photoinduced Charge Separation and Structural Relaxation in the CT State

et al. 2003

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Electron donor-acceptor systems with phenothiazine linked directly to pyrene exhibit a dual emission in moderately and very polar solvents. Steady state and time-resolved fluorescence spectroscopy provide evidence that the "blue" and "red" emission bands originate from different species. Fluorescence excitation spectra show a similar appearance when the emission is monitored either in the red or blue spectral range, but they are slightly shifted against each other. This suggests that different isomers exist with a distinctly different photophysical behavior. Semiempirical (AM1/CI) molecular orbital calculations with a continuum solvent treatment have been used to establish the geometry of the two nearly isoenergetic stereoisomers and to calculate the properties of their excited Franck-Condon states. Geometry optimization of various excited states provides evidence for different internal relaxation coordinates for the phenothiazine-localized S 1 state and the charge transfer state S 6 , on one hand, and the pyrene-localized S 2 (S 3 ) state, on the other hand. The relaxed geometries in the excited states of both isomers represent mirror images with identical properties. The different photophysical behavior of the two isomers is most likely caused by the different potential energy curves, or more precisely speaking, by different location and/or heights of the barrier along the reaction coordinates from the locally excited to the geometry-relaxed CT states.

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Section: Stabilization Of Ct States By Solvent and Geometricalsupporting

confidence: 90%

Phenothiazine−Pyrene Dyads: Photoinduced Charge Separation and Structural Relaxation in the CT State

et al. 2003

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“…A careful analysis of light-induced reactions will eventually lead us to an improved understanding of the timedependent dielectric in the interiors of membranes. Relevant experiments are now emerging (see, for example, Alkaitis, Gratzel & Henglein, 1975).…”

Section: (4) the Spectra Of Proteinsmentioning

confidence: 99%

Calculations of electrostatic interactions in biological systems and in solutions

Warshel

Russell

1984

Quart. Rev. Biophys.

1,010

915

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Correlating the structure and action of biological molecules requires knowledge of the corresponding relation between structure and energy. Probably the most important factors in such a structure– energy correlation are associated with electrostatic interactions. Thus the key requirement for quantative understanding of the action of biological molecules is the ability to correlate electrostatic interactions with structural information. To appreciate this point it is useful to compare the electrostatic energy of a charged amino acid in a polar solvent to the corresponding van der Waals energy. The electrostatic free energy, ΔGel, can be approximated (as will be shown in Section II) by the Born formula (ΔGel = –(166Q2/ā) (I – I/E)). Where ΔGel is given in kcal/mol, Qis the charge of the given group, in units of electron charge, āis the effective radius of the group, and E is the dielectric constant of the solvent. With an effective radius of charged amino acids of approximately 2 Å, Born's formula gives about – 80 kcal/mol for their energy in polar solvents where E is larger than 10. This energy is two orders of magnitude larger than the van der Waals interaction of such groups and their surroundings.

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“…17). 60 _Yj ' " 1 CH,-CHiCH,-CHiCH,-CHfCH,-CH,-CH,-CH,-CH,-CHiCH,-CHjCH, In the case of photolysis of mixed micelles of SLS and the 4-benzoylbenzoate anion (15) hydrogen abstraction from the detergent backbone methylene groups occurs and is followed by attachment of the benzophenone moiety to the detergent. Abstraction occurs from over positions 5 to 11 of the chain.…”

Section: Intermolecular Hydrogen Abstraction Reactionsmentioning

confidence: 99%

Photophysical and Photochemical Processes in Micellar Systems

Turro

Grätzel

Braun

1980

Angew. Chem. Int. Ed. Engl.

403

191

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A fascinating feature inherent to aqueous surfactant solutions is the phenomenon of self-organization: above a certain critical concentration (the critical micelle concentration, CMC) detergent molecules associate spontaneously to build up structural entities of colloidal dimensions called micelles. The architecture of these agglomerates is such that the interior contains the hydrophobic alkyl chain of the amphiphile while the hydrophilic head groups are located at the surface and are in contact with bulk water. In the case of ionic micelles the interface is charged giving rise to an electrical double layer and a potential difference of up to several hundred millivolts between the micellar pseudophase and water. Thus micellar systems are microheterogeneous in character: the electrostatic potential and polarity prevailing in the interior of the aggregate differ from those of the bulk aqueous phase. A particularly attractive aspect of photochemical studies in micellar systems is the possibility of organizing the reactants at a molecular level: by comparison of the data in micelles with similar data in homogeneous solution one can learn about the molecular details of a given reaction and establish which conditions favor one pathway or another. In simpIe surfactant systems differences in rate and efficiency of a reaction will often be controlled by local electrostatic potentials and the compartmentalization of the reagents within the surfactant aggregates. Through the latter effect the statistics of probe distribution over the micelles becomes important in controlling fast photochemical events. Functional micelles are distinguished by the fact that the surfactant molecule contains a group which itself participates in the photoprocess. These units are unique in that self-assembly often introduces striking cooperative effects.

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Laser Photo‐Ionization of Phenothiazine in Micellar Solution II: Mechanism and Light Induced Redox Reactions with Quinones

Cited by 55 publications

References 16 publications

Phenothiazine−Pyrene Dyads: Photoinduced Charge Separation and Structural Relaxation in the CT State

Phenothiazine−Pyrene Dyads: Photoinduced Charge Separation and Structural Relaxation in the CT State

Calculations of electrostatic interactions in biological systems and in solutions

Photophysical and Photochemical Processes in Micellar Systems

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