Electronic and Molecular Structures of Dyes VI: Estimation of Redox Potentials and Excitation Energies of Cyanine Dyes by Means of HMO Calculation with Regard to Steric Effects.

1971 ◽  
Vol 19 (6) ◽  
pp. 161-166 ◽  
Author(s):  
T. Tani
Keyword(s):  
Cyanine Dyes ◽  
Molecular Structures ◽  
Steric Effects ◽  
Redox Potentials ◽  
Excitation Energies

Unexpected formation and conversion: role of substituents of 1,3-ynones in the reactivity and product distribution during their reactions with Ru3(CO)12

2019 ◽  
Vol 43 (3) ◽  
pp. 1478-1486
Author(s):  
Lei Xu ◽  
Liping Jiang ◽  
Shasha Li ◽  
Guofang Zhang ◽  
Weiqiang Zhang ◽  
...  
Keyword(s):  
Product Distribution ◽  
Molecular Structures ◽  
Steric Effects ◽  
Unexpected Formation ◽  
Electronic And Steric Effects

Electronic and steric effects of the substituents in 1,3-ynones play key roles in the product distribution and molecular structures.

Steric effects on the electronic and molecular structures of nickel(II) and cobalt(II) 2,6-dipyrazol-1-ylpyridine complexes

Polyhedron ◽  
2001 ◽  
Vol 20 (22-23) ◽  
pp. 2829-2840 ◽  
Author(s):  
Joanne M. Holland ◽  
Colin A. Kilner ◽  
Mark Thornton-Pett ◽  
Malcolm A. Halcrow
Keyword(s):  
Molecular Structures ◽  
Steric Effects

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.

Synthesis of Heterocyclic Monomers Designed to Produce Conducting Polymer with Specific Redox Requisites and to Evaluate Stereochemical Factors Influencing the Conductivity

1992 ◽  
Vol 247 ◽  
Author(s):  
Anna Berlin ◽  
Elisabetta Brenna ◽  
Giorgio. A. Pagani ◽  
Franco Sannicolo ◽  
Gianni Zotti ◽  
...  
Keyword(s):  
Twist Angle ◽  
Conductive Polymer ◽  
Type Systems ◽  
Molecular Structures ◽  
Ring Size ◽  
Redox Potentials ◽  
Central Ring ◽  
Crystal And Molecular Structures ◽  
Factors Influencing ◽  
Saturated Chain

ABSTRACTAccording to the “spacer” strategy we have previously proposed the monomers candidate for providing conductive polymers endowed with special properties should contain the polymerogenic rings (pyrrole or thiophene), as terminal units, linked to a central π-conjugatively active frame; we describe how it is possible in this way to control the redox potentials E of the polymers derived from such monomers. This control is beneficial because it is possible to increase the E° value of polypyrrole-type systems and decreases the E° value of polythiophene-type systems. Also, the “spacer”may be further functionalised and, being remote from the polymerisation site, cannot alter the conductivity characteristics typical of the polymer derived from the parent heterocycle (pyrrole or thiophene): such a functionalisation may provide the final, tailored, conductive polymer with special properties (e.g. solubility). If the central ring, acting as a spacer, is formed linking two positions of a di-heterocycle with a saturated chain, it is possible to partially control the twist angle between the heterocyclic units. Crystal and molecular structures have shown that dipyrrole units further linked through the nitrogen atoms are quite sensitive to the central ring size. With respect to the conductivity of unsubstituted polypyrrolc, the conductivity of the polymers derived from such monomers is dependent from the twist angle between the rings. This result is relevant to describe conditions of conjugation between the heterocyclic units of a monomer required to produce upon doping a conductive polymer.

THE CRYSTAL AND MOLECULAR STRUCTURES OF m-DINITROBENZENE AND p-DINITROBENZENE

1961 ◽  
Vol 39 (8) ◽  
pp. 1638-1644 ◽  
Author(s):  
J. Trotter
Keyword(s):  
Three Dimensional ◽  
Molecular Structures ◽  
Steric Effects ◽  
Crystal And Molecular Structures

The structures of m-dinitrobenzene and p-dinitrobenzene have been refined by three-dimensional (Fo—Fc) syntheses. The results indicate that both nitro groups in each molecule are twisted 11° out of the aromatic plane, about the C—N bonds, in contrast to nitrobenzene, where the whole molecule is completely planar. These molecular configurations are shown to be in accord with those which might be expected from intramolecular steric effects. The dimensions of the three molecules have also been compared.

Regularized regression analysis of digitized molecular structures in organic reactions for quantification of steric effects

2017 ◽  
Vol 38 (21) ◽  
pp. 1825-1833 ◽  
Author(s):  
Shigeru Yamaguchi ◽  
Takahiro Nishimura ◽  
Yuta Hibe ◽  
Masaki Nagai ◽  
Hirofumi Sato ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Molecular Structures ◽  
Organic Reactions ◽  
Steric Effects ◽  
Regularized Regression

scholarly journals Basicity of N5 in semiquinone enhances the rate of respiratory electron outflow inShewanella oneidensisMR-1

2019 ◽  
Author(s):  
Yoshihide Tokunou ◽  
Keisuke Saito ◽  
Ryo Hasegawa ◽  
Kenneth H. Nealson ◽  
Kazuhito Hashimoto ◽  
...  
Keyword(s):  
Free Energy ◽  
Electron Transport ◽  
Nitrogen Atom ◽  
Outer Membrane ◽  
Diffusion Constant ◽  
Shewanella Oneidensis ◽  
Molecular Structures ◽  
Redox Potentials ◽  
Transport Reaction ◽  
Extracellular Electron Transport

AbstractExtracellular electron transport (EET) occurs in environmental iron-reducing bacteria and is mediated by an outer membrane multi-heme cytochrome complex (Cyts). It has critical implications for global mineral cycling and electrochemical microbial catalysis. The rate of EET mediated by multiple heme redox centers significantly increases in the presence of flavins and quinones. Their electron free energy does not entirely account for the fact that differential effects on EET rate enhancement vary significantly by factors ≥100. Here, we report on whole-cell electrochemical analysis ofShewanella oneidensisMR-1 using six flavin analogs and four quinones. We demonstrated that protonation of the nitrogen atom at position 5 (N5) of the isoalloxazine ring is essential for electron outflow acceleration as a bound non-covalent cofactor of Cyts. EET mediated by Cyts was accelerated at a rate dependent on pKa(N5). The EET rate largely decreased in response to the addition of deuterated water (D2O), while low concentration of D2O (4 %) had little impact on electron free energy difference of the heme and non-covalent bound cofactors, strongly suggesting that the protonation of N5 limits the rate of EET. Our findings directly link EET kinetics to proton transport reaction via N5 and provide a basis for the development of novel strategies for controlling EET-associated biological reactions.Significance statementThe potential of various small molecules such as flavins and quinones to enhance the rate of extracellular electron transport (EET) has been exploited to develop environmental energy conversion systems. Flavins and quinones have similar molecular structures but their abilities to enhance EET vary by >100× inShewanella oneidensisMR-1. These large differences are inconsistent with conventional models, which rely on redox potentials or diffusion constant of shuttling electron mediators. In this study, we demonstrated that the basicity of the nitrogen atom of the isoalloxazine ring (N5) enhances the rate of electron outflow when a flavin or quinone is a non-covalent cofactor ofS. oneidensisMR-1 outer membranec-type cytochromes.

Preparation, crystal and molecular structures of Ph2CNSNSO and a comparison of the —SNSO and —SNSS chromophores

1985 ◽  
Vol 63 (5) ◽  
pp. 1063-1067 ◽  
Author(s):  
Tristram Chivers ◽  
Richard T. Oakley ◽  
Roger Pieters ◽  
John F. Richardson
Keyword(s):  
Thermal Decomposition ◽  
Molecular Structures ◽  
Structural Determination ◽  
Model Compounds ◽  
Excitation Energies ◽  
Space Group ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Mndo Calculations

The sulphenyl chloride, Ph2CNSCl, prepared insitu from Ph2CNSiMe3 and sulphur dichloride, has been employed in the synthesis of Ph2CNSNSO and Ph2CNSNSNSNCPh2 by reaction with Me3SiNSO and Me3SiNSNSiMe3, respectively. An X-ray structural determination of Ph2CNSNSO shows it to consist of a planar cis-trans chain. The crystals are triclinic and belong to the space group[Formula: see text], a = 9.9078(8), b = 10.0967(9), c = 15.1682(14) Å, α = 78.646(7), β = 71.065(7), γ = 63.449(7)°, V = 1281.5(5) Å3, Z = 4. The final R and Rw values were 0.033 and 0.027, respectively. The π* → π* excitation energies for the RSNSO and RSNSS chromophores are compared for different R groups and discussed in the light of MNDO calculations on the model compounds HSNSX (X = S, O). The thermal decomposition of both Ph2CNSNSO and Ph2CNSNSNSNCPh2 produced S4N4 and Ph2CO or (Ph2CN)2S, respectively.

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