scholarly journals Stereoelectronic control of oxidation potentials of 3,7-bis(diarylamino)phenothiazines

RSC Advances ◽  
2017 ◽  
Vol 7 (88) ◽  
pp. 56144-56152 ◽  
Author(s):  
Ayumu Karimata ◽  
Shuichi Suzuki ◽  
Masatoshi Kozaki ◽  
Keiji Okada
Keyword(s):  
Conformational Changes ◽  
Substituent Effect ◽  
Oxidation Process ◽  
Oxidation Potentials ◽  
Stereoelectronic Control

We found a unique stereoelectronic-substituent effect on the oxidation potentials of bis(diarylamino)phenothiazines through large conformational changes during the oxidation process.

The effect of substituents on the electrochemical oxidation potentials of 1,1,2,2-tetraphenylcyclopropane and 1,1,3,3-tetraphenylpropenyl radical

1986 ◽  
Vol 64 (1) ◽  
pp. 100-103 ◽  
Author(s):  
Danial D. M. Wayner ◽  
Donald R. Arnold
Keyword(s):  
Electron Transfer ◽  
Transition State ◽  
Transfer Process ◽  
Substituent Effect ◽  
Oxidation Process ◽  
Oxidation Potential ◽  
Slow Electron ◽  
Electron Transfer Process ◽  
Oxidation Potentials ◽  
Multiple Substitution

The effects of multiple substitution by methoxy and cyano in the 4-position(s) of 1,1,2,2-tetraphenylcyclopropane (1) and 1,1,3,3-tetraphenylpropenyl radical (2•) on the oxidation potentials have been measured. The results indicate that the oxidation process for the cyclopropanes (1a–m) is irreversible. Nevertheless, the substituent effect on the potential is essentially additive and correlates reasonably well with Σσ+. A slow electron transfer process (an overall conversion of 1 to 2+), with a transition state resembling the ring-opened radical cation, is consistent with these observations. The oxidation of the radical 2• is quasi-reversible in dichloromethane. In this case also, the substituent effect on the oxidation potential is additive and correlates with Σσ+. Any deviation from planarity of 2• is not sufficient to prevent substituents from exerting normal (additive) behaviour.

Substituent Effect of Bis(pyridines)iodonium Complexes as Iodinating Reagents: Control of the Iodocyclization/Oxidation Process

2013 ◽  
Vol 19 (16) ◽  
pp. 4992-4996 ◽  
Author(s):  
Takashi Okitsu ◽  
Saki Yumitate ◽  
Kana Sato ◽  
Yasuko In ◽  
Akimori Wada
Keyword(s):  
Substituent Effect ◽  
Oxidation Process

Stereo-Electronic Effects in Substituted Phosphines: a Molecular Orbital Study

1985 ◽  
Vol 38 (1) ◽  
pp. 23 ◽  
Author(s):  
E Magnusson
Keyword(s):  
Molecular Orbital ◽  
Conformational Changes ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Steric Effects ◽  
Electronic Effects ◽  
Electronic Response ◽  
Donor Acceptor ◽  
Geometrical Change

Substituent effects from directly bonded and remote groups in phosphines have been studied by ab initio molecular orbital methods in an attempt to discriminate between the electronic and steric effects of attached groups and determine how they are transmitted to phosphorus. Results of calculations are compared with experimentally determined basicities and acidities, ionization energies, inversion barriers and 31P N.M.R. results. The electronic consequences of steric effects are comparable in importance to direct electronic effects; in the PHn(CH3)3-n, series steric effects account for about half of the substituent effect on basicities and ionization potentials. The effects of steric bulk, modelled by bond angle constraint, are concentrated in the HOMO; by contrast, electronic effects on the HOMO are often minimal. Conformational changes include changes in geometry but the electronic response exceeds what would be expected for geometrical change alone and in NH2- and OH-substituted model compounds of the PH2X and PX3 series may be as great as that produced by changing the substituent. In remote substitution the effects are mainly due to charge displacement at phosphorus. Directly bound groups more often exert their effects by altering the balance between s and p orbitals in the bonding and in the non-bonding parts of the electron distribution but in ways which preclude correlation with electronegativity or other single-parameter measures of substituent properties. Donor/acceptor interactions are weaker in phosphorus(III) compounds than in the first-row analogues but the response to substitution in the density profile is much stronger around the more polarizable second-row element which explains why the alkyl substituent effect is greater for the donor properties of phosphines than amines while the effects of fluoro-substitution are weaker.

ChemInform Abstract: Substituent Effect of Bis(pyridines)iodonium Complexes as Iodinating Reagents: Control of the Iodocyclization/Oxidation Process.

ChemInform ◽  
2013 ◽  
Vol 44 (34) ◽  
pp. no-no
Author(s):  
Takashi Okitsu ◽  
Saki Yumitate ◽  
Kana Sato ◽  
Yasuko In ◽  
Akimori Wada
Keyword(s):  
Substituent Effect ◽  
Oxidation Process

Substituent and charge distribution effects on the redox potentials of radicals. Thermodynamics for homolytic versus heterolytic cleavage in the 1-naphthylmethyl system

1992 ◽  
Vol 70 (1) ◽  
pp. 121-127 ◽  
Author(s):  
Paul H. Milne ◽  
Danial D. M. Wayner ◽  
Dayal P. DeCosta ◽  
James A. Pincock
Keyword(s):  
Charge Density ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Radical Cations ◽  
Relative Magnitude ◽  
Redox Potentials ◽  
Heterolytic Cleavage ◽  
Reduction Potentials ◽  
Oxidation Potentials ◽  
Interesting Conclusion

The electrochemical oxidation and reduction potentials of a number of substituted 1-methylnaphthalenes (1a-l) and 1-naphthylmethyl radicals (2a-l•) as well as 2-methylnaphthalene (3) and the 2-naphthylmethyl radical (4•) have been measured by cyclic voltammetry and photomodulation voltammetry. The oxidation potentials correlate with σ+ (ρ+ = −7.1 and −8.4 for 1 and 2• respectively) while the reduction potentials correlate with σ− (ρ− = 10.1 and 13.0 for 1 and 2• respectively). The relative magnitude of the ρ values can be rationalized when the charge density distribution in these systems is considered. This leads to the interesting conclusion that even though a full charge is placed in the π-system of 1 when it is oxidized or reduced, the fraction of the charge that accumulates at C4 is actually less than in 2+ or 2− where only 50–70% of the charge is delocalized into the ring. A correlation between ρ for the redox reactions of 1, 2•, benzyl, diphenylmethyl, and cumyl and the calculated (AM1) charge density at C4 is established, implying that the sensitivity of the corresponding ions to substituent effects increases as the fraction of charge at that site increases. The redox data have been used in thermochemical cycles in order to estimate the substituent effect on the homolytic, mesolytic, and heterolytic cleavage reactions of 1 and its corresponding radical ions. The implication of these results on the C—C cleavage versus deprotonation of radical cations and on the photochemical homolysis versus heterolysis of naphthylmethyl halides and acetates is discussed. Keywords: electrochemistry, homolysis, heterolysis, naphthylmethyl, substituent effect.

The Mechanism of Hydrolysis of Imidate Salts. The Importance of Stereoelectronic Control and pH of the Reaction Medium on the Cleavage of Tetrahedral Intermediates

1975 ◽  
Vol 53 (20) ◽  
pp. 3029-3037 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Roland J. Taillefer
Keyword(s):  
Conformational Changes ◽  
Entire Range ◽  
Reaction Medium ◽  
Tetrahedral Intermediate ◽  
Mechanism Of Hydrolysis ◽  
Stereoelectronic Control ◽  
Neutral Conditions ◽  
Hydrolysis Of ◽  
Ionic Forms ◽  
Tetrahedral Intermediates

Hydrolysis of anti imidate salts give the ester amine products exclusively over the entire range of pH. Hydrolysis of syn imidate salts in acidic and neutral conditions give the ester amine products only; in basic conditions, mixtures of ester amine and amide alcohol products are observed. These results are explained by the application of the new theory of stereoelectronic control on the various ionic forms T+, T±, and T− of the tetrahedral intermediate. For syn imidate salts, conformational changes of the tetrahedral intermediate must occur in order to have cleavage with stereoelectronic control.

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

Control of Metal Alloy Oxidation with Electric Fields

1973 ◽  
Vol 31 ◽  
pp. 164-165
Author(s):  
R. R. Dils ◽  
P. S. Follansbee
Keyword(s):  
Electric Fields ◽  
Oxidation Process ◽  
Base Alloy ◽  
Oxide Surface ◽  
Platinum Electrodes ◽  
Insulating Layer ◽  
Iron Base Alloy ◽  
Alloy Oxidation ◽  
Aluminum Oxide Layer ◽  
And Control

Electric fields have been applied across oxides growing on a high temperature alloy and control of the oxidation of the material has been demonstrated. At present, three-fold increases in the oxidation rate have been measured in accelerating fields and the oxidation process has been completely stopped in a retarding field.The experiments have been conducted with an iron-base alloy, Pe 25Cr 5A1 0.1Y, although, in principle, any alloy capable of forming an adherent aluminum oxide layer during oxidation can be used. A specimen is polished and oxidized to produce a thin, uniform insulating layer on one surface. Three platinum electrodes are sputtered on the oxide surface and the specimen is reoxidized.

Structural Imperfections in thin Oxide Films Formed on Some Fe- and Ni-Base Alloys

1970 ◽  
Vol 28 ◽  
pp. 510-511
Author(s):  
L. P. Lemaire ◽  
D. E. Fornwalt ◽  
F. S. Pettit ◽  
B. H. Kear
Keyword(s):  
Oxide Scale ◽  
Oxidation Process ◽  
Short Circuit ◽  
Protective Oxide ◽  
Protective Oxide Scale ◽  
Thin Oxide Films ◽  
Diffusion Paths ◽  
Oxidation Resistant ◽  
Structural Imperfections ◽  
Short Circuit Diffusion

Oxidation resistant alloys depend on the formation of a continuous layer of protective oxide scale during the oxidation process. The initial stages of oxidation of multi-component alloys can be quite complex, since numerous metal oxides can be formed. For oxidation resistance, the composition is adjusted so that selective oxidation occurs of that element whose oxide affords the most protection. Ideally, the protective oxide scale should be i) structurally perfect, so as to avoid short-circuit diffusion paths, and ii) strongly adherent to the alloy substrate, which minimizes spalling in response to thermal cycling. Small concentrations (∼ 0.1%) of certain reactive elements, such as yttrium, markedly improve the adherence of oxide scales in many alloy systems.

Role of spectrin in membrane fusion and in shape change of human erythrocyte ghost

1978 ◽  
Vol 36 (2) ◽  
pp. 328-329
Author(s):  
Hideo Hayashi ◽  
Yoshikazu Hirai ◽  
John T. Penniston
Keyword(s):  
Conformational Changes ◽  
Human Erythrocyte ◽  
Shape Change ◽  
Membrane Surface ◽  
Slight Modification ◽  
Active Role ◽  
Main Role ◽  
Bank Blood ◽  
Human Erythrocyte Ghost

Spectrin is a membrane associated protein most of which properties have been tentatively elucidated. A main role of the protein has been assumed to give a supporting structure to inside of the membrane. As reported previously, however, the isolated spectrin molecule underwent self assemble to form such as fibrous, meshwork, dispersed or aggregated arrangements depending upon the buffer suspended and was suggested to play an active role in the membrane conformational changes. In this study, the role of spectrin and actin was examined in terms of the molecular arrangements on the erythrocyte membrane surface with correlation to the functional states of the ghosts.Human erythrocyte ghosts were prepared from either freshly drawn or stocked bank blood by the method of Dodge et al with a slight modification as described before. Anti-spectrin antibody was raised against rabbit by injection of purified spectrin and partially purified.

Sign in / Sign up

Export Citation Format

Share Document