Correlation of the photoelectron and electronic spectra of thiochromones and thiochromanones with their electrochemical data

1979 ◽  
Vol 57 (6) ◽  
pp. 638-644 ◽  
Author(s):  
Rafik O. Loutfy ◽  
Ian W. J. Still ◽  
Michael Thompson ◽  
Toong S. Leong
Keyword(s):  
Gas Phase ◽  
Substituent Effects ◽  
Spectroscopic Properties ◽  
Oxidation Potential ◽  
Molecular Orbitals ◽  
Absolute Difference ◽  
Linear Free Energy Relationship ◽  
Redox Potentials ◽  
Reduction Potentials ◽  
Oxidation Potentials

The gas phase ionization potentials, electrochemical redox potentials and spectroscopic properties of a series of thiochroman-4-one and thiochromone derivatives have been studied. A dramatic shift in the energies of the lowest vacant and highest occupied molecular orbitals of the parent thiochromanone as a function of the addition of a double bond and/or oxidation of the sulphur atom was observed. This shift in energy of the molecular orbitals was reflected in their spectroscopic characteristics. The lowest singlet (and triplet) state of compounds 1–3 in solution is π,π* in nature, while that of compounds 4–6 is n,π*. These results are best explained in terms of substituent effects on the energetics of the acetophenone moiety. The change in the nature of the lowest excited state from π,π* (1–3) to n,π* (4–6) should result in quite different types of photochemistry for the two series.A linear free-energy relationship between the singlet and triplet energies and the absolute difference between the oxidation and reduction potentials of the two series was found. These correlations have been utilized to estimate the half-wave oxidation potentials of compounds 3–6. A correlation was found to exist between the gas phase ionization potential and the solution electrochemical oxidation potential.

The interrelation between polarographic half-wave potentials and the energies of electronic excited states

1976 ◽  
Vol 54 (9) ◽  
pp. 1454-1463 ◽  
Author(s):  
Rafik O. Loutfy ◽  
Raouf O. Loutfy
Keyword(s):  
Excited States ◽  
Coulomb Repulsion ◽  
Oxidation Potential ◽  
Absolute Difference ◽  
Linear Free Energy Relationship ◽  
Electronic Excited States ◽  
Reduction Potentials ◽  
Linear Free Energy ◽  
Half Wave ◽  
Experimental Parameters

The polarographic half-wave oxidation and reduction potentials, singlet and triplet energies of a series of (i) monocyclic aza-aromatics, (ii) polycyclic aza-aromatics and their N-oxides, (iii) condensed aromatic hydrocarbons, and (iv) substituted benzene derivatives are reported. The interrelation between the spectroscopic and electrochemical data is developed and discussed in regard to theoretical and experimental parameters. A linear free-energy relationship between the triplet energies and the absolute difference between the oxidation and reduction potentials of the first three series was found. These correlations were utilized to estimate the triplet energies of other molecules in the series, to predict the true half-wave oxidation potential of some heteroaromatic N-oxides and to compute the coulomb repulsion integral. No correlation between ET(π, π*) and (E1/2°x − E1/2R) for substituted benzenes was found. The various reasons for this deviation were discussed.

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.

Synthesis and hydrolysis of gas-phase lanthanide and actinide oxide nitrate complexes: a correspondence to trivalent metal ion redox potentials and ionization energies

2015 ◽  
Vol 17 (15) ◽  
pp. 9942-9950 ◽  
Author(s):  
Ana F. Lucena ◽  
Célia Lourenço ◽  
Maria C. Michelini ◽  
Philip X. Rutkowski ◽  
José M. Carretas ◽  
...  
Keyword(s):  
Gas Phase ◽  
Metal Ion ◽  
Oxidation States ◽  
Redox Potentials ◽  
Trivalent Metal ◽  
Ionization Energies ◽  
Reduction Potentials ◽  
Hydrolysis Of ◽  
Nitrate Complexes

Gas-phase hydrolysis of lanthanide/actinide MO3(NO3)3−ions relates to the stabilities of the MIVoxidation states, which correlate with IV/III solution reduction potentials and 4th ionization energies.

Photoswitching of Redox Potentials and Spectroscopic Properties in the UV/vis Region

2005 ◽  
Vol 60 (1) ◽  
pp. 75-82 ◽  
Author(s):  
Nedko Drebov ◽  
Nikolai Tyutyulkov ◽  
Stojan Karabunarliev ◽  
Fritz Dietz
Keyword(s):  
Spectroscopic Properties ◽  
Visible Spectral Region ◽  
Redox Potentials ◽  
Electron Systems ◽  
Excitation Energies ◽  
Reduction Potentials ◽  
Open Ring ◽  
Wavelength Absorption ◽  
Donor Acceptor ◽  
Ct Transitions

The photoswitching of optical and electrochemical properties of di-donor, di-acceptor and donor-acceptor substituted photochromic tetrahydropyrene - [2,2]metacyclophanene and dihydropyrene - [2,2]metacyclophanediene systems has been studied theoretically. A switching of the halfwave oxidation and reduction potentials should be possible in the case of bis(pyridinium) and bis(hydroxyphenyl) substituted systems. Because of the relatively great perturbation of the planarity of the π-electron systems by large torsion of the substituents out of the π-electron structure of the photochromic system and the stair-like structure of the ring-opened isomer, relatively large excitation energies for CT transitions have been calculated with the AM1-CI procedure. The ring-closed structures should absorb in the visible spectral region, and the open-ring isomers should have a longest-wavelength absorption in the UV region.

Effects of Doping on the Electrochemical and Electrical Properties of Poly(2,5-di(2-thienyl)pyrrole)

1999 ◽  
Vol 64 (8) ◽  
pp. 1357-1368 ◽  
Author(s):  
Enric Brillas ◽  
José Carrasco ◽  
Ramon Oliver ◽  
Francesc Estrany ◽  
Víctor Ruiz
Keyword(s):  
Mass Spectrometry ◽  
Fast Atom Bombardment ◽  
Oxidation Potential ◽  
Ethanolic Solution ◽  
Pt Electrode ◽  
Reversible Process ◽  
Oxidation Potentials ◽  
Lower Productivity ◽  
Polymeric Chains ◽  
Linear Molecules

The electropolymerization of 2,5-di(2-(thienyl)pyrrole) (SNS) on a Pt electrode from ethanolic solution with LiClO4 or LiCl as electrolyte has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). In both media, a quasi-reversible process has been indicated by CV, reversing the scan at low oxidation potentials. Under these conditions, reducible positive charges formed in both oxidized polymers are compensated by the entrance of anions from solution. Elemental analysis reveals that polymers generated at a low oxidation potential by CA contain a 21.03% (w/w) of ClO4- or a 9.56% (w/w) of Cl-. The poly(SNS) doped with Cl- presents higher proportion of reducible positive charges, higher polymerization charge and lower productivity. A much higher electrical conductivity, however, has been found for the poly(SNS) doped with ClO4-. Both polymers are soluble in DMSO, acetone and methanol. The dimer, trimer, tetramer and pentamer have been detected as soluble and neutral linear oligomers by mass spectrometry-fast atom bombardment. The analysis of polymers by infrared spectroscopy confirms the predominant formation of linear molecules with α-α linkages between monomeric units. A condensation mechanism involving one-electron oxidation of all electrogenerated linear and neutral polymeric chains is proposed to explain the SNS electropolymerization.

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