Organometallic superacids and hyperacids: Acidity enhancement by internal bonding with a strong electron-pair acceptor group BX2

2021 ◽  
Vol 763 ◽  
pp. 138207
Author(s):  
Younes Valadbeigi ◽  
Jean-François Gal
Keyword(s):  
Electron Pair ◽  
Internal Bonding ◽  
Strong Electron ◽  
Acceptor Group

scholarly journals Taming Super Lewis Acids for Catalysis: The Family of Ferrocene-Stabilized Silicon Cations

2014 ◽  
Author(s):  
Martin Oestreich ◽  
Hendrik Klare ◽  
Kristine Müther ◽  
Roland Fröhlich
Keyword(s):  
Low Temperatures ◽  
Lewis Acids ◽  
Acid Catalysis ◽  
Electron Pair ◽  
Reaction Rates ◽  
Diels Alder ◽  
Strong Electron ◽  
The Family ◽  
Electron Deficiency

Tricoordinate silicon cations are exceptionally strong electron pair acceptors, so strong that they react with almost any σ and π basic molecule. In order to use such reactive intermediates in synthetic chemistry, Lewis acid catalysis in particular, we have designed intramolecularly stabilized silylium ions whose electron deficiency is attenuated by an adjacent, electron-rich ferrocenyl fragment. Here we wish to present the synthesis and structural characterization of these unique transition metal-stabilized silicon cations which reveal an unprecedented bonding situation different from its isoelectronic analogues. The potential of this motif is further highlighted in challenging Diels–Alder reactions, which are catalyzed at low temperatures with exceptional reaction rates and selectivities.

Two Excited State Structures of Donor-Acceptor Substituted "Proton Sponge"

2005 ◽  
Vol 277-279 ◽  
pp. 1060-0 ◽  
Author(s):  
A. Szemik Hojniak ◽  
I. Deperasińska ◽  
W.J. Buma ◽  
G. Balkowski ◽  
A.F. Pozharsky ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Ground State ◽  
Experimental Spectrum ◽  
Proton Sponge ◽  
Strong Electron ◽  
Acceptor Group ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Ab Initio Hf

Photoexcitation of “proton sponge” 1,8-bis (dimethylamino) naphthalene (DMAN) leads to charge transfer (CT) emission. This work demonstrates that substitution of DMAN with a strong electron acceptor group (CN) results in CN-DMAN and leads to a stronger orbital decoupling between the Donor and Acceptor groups and to a more effective CT process (λF = 630 nm). The theoretical absorption spectrum calculated for CN-DMAN using the ZINDO method on its ground state ab initio [HF/6-31G(d)] optimized geometry reproduces a better experimental spectrum than that calculated using the RCIS method. It also shows that AM1 excited state (1La) optimization reveals two quasi-degenerated states with anti-quinoidal (A) and quinoidal (B) structures and the CT nature. Both structures may contribute more or less equally to the fluorescence of CN-DMAN in a solution.

scholarly journals Push-Pull Heterocyclic Dyes Based on Pyrrole and Thiophene: Synthesis and Evaluation of Their Optical, Redox and Photovoltaic Properties

Coatings ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 34
Author(s):  
Sara S. M. Fernandes ◽  
Maria Cidália R. Castro ◽  
Dzmitry Ivanou ◽  
Adélio Mendes ◽  
Maria Manuela M. Raposo
Keyword(s):  
Electron Donor ◽  
Oxidation Potential ◽  
Cyanoacetic Acid ◽  
Strong Electron ◽  
Photovoltaic Properties ◽  
Heterocyclic Molecules ◽  
Acceptor Group ◽  
Donor Acceptor ◽  
Ethoxyl Group ◽  
Anchoring Groups

Three heterocyclic dyes were synthesized having in mind the changes in the photovoltaic, optical and redox properties by functionalization of 5-aryl-thieno[3,2-b]thiophene, 5-arylthiophene and bis-methylpyrrolylthiophene π-bridges with different donor, acceptor/anchoring groups. Knoevenagel condensation of the aldehyde precursors with 2-cyanoacetic acid was used to prepare the donor-acceptor functionalized heterocyclic molecules. These organic metal-free dyes are constituted by thieno[3,2-b]thiophene, arylthiophene, bis-methylpyrrolylthiophene, spacers and one or two cyanoacetic acid acceptor groups and different electron donor groups (alkoxyl, and pyrrole electron-rich heterocycle). The evaluation of the redox, optical and photovoltaic properties of these compounds indicate that 5-aryl-thieno[3,2-b]thiophene-based dye functionalized with an ethoxyl electron donor and a cyanoacetic acid electron acceptor group/anchoring moiety displays as sensitizer for DSSCs the best conversion efficiency (2.21%). It is mainly assigned to the higher molar extinction coefficient, long π-conjugation of the heterocyclic system, higher oxidation potential and strong electron donating capacity of the ethoxyl group compared to the pirrolyl moiety.

Evidence for Strong Electron-Electron Correlations in (MTPP)1-x (MTPA)X (TCNQ)2

1982 ◽  
Vol 85 (1) ◽  
pp. 225-231
Author(s):  
G. Croteau ◽  
Amir Lakhani ◽  
N. K. Hota
Keyword(s):  
Electron Correlations ◽  
Strong Electron

Electron Donation by Low-Crystalline Ba-La-Ce Oxygen-Deficient Composite Oxide Accumulating on Ru Nanoparticles for Ammonia Synthesis under Mild Conditions

2019 ◽  
Author(s):  
Katsutoshi Sato ◽  
Shin-ichiro Miyahara ◽  
Yuta Ogura ◽  
Kotoko Tsujimaru ◽  
Yuichiro Wada ◽  
...  
Keyword(s):  
Ammonia Synthesis ◽  
Bond Cleavage ◽  
Synthesis Process ◽  
Strong Electron ◽  
Mild Conditions ◽  
Ru Nanoparticles ◽  
Rate Determining Step ◽  
Highly Active ◽  
Composite Oxides ◽  
Low Crystalline

<p>To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity of Ru/Ba/LaCeO<i><sub>x</sub></i> pre-reduced at 700 °C is the highest reported among oxide-supported Ru catalysts. Our results indicate that low crystalline oxygen-deficient composite oxides, which include Ba<sup>2+</sup>, Ce<sup>3+</sup> and La<sup>3+</sup>, with strong electron-donating ability, accumulate on Ru particles and thus promote N≡N bond cleavage, which is the rate determining step for ammonia synthesis.</p>

Electron Donation by Low-Crystalline Ba-La-Ce Oxygen-Deficient Composite Oxide Accumulating on Ru Nanoparticles for Ammonia Synthesis under Mild Conditions

2019 ◽  
Author(s):  
Katsutoshi Sato ◽  
Shin-ichiro Miyahara ◽  
Yuta Ogura ◽  
Kotoko Tsujimaru ◽  
Yuichiro Wada ◽  
...  
Keyword(s):  
Ammonia Synthesis ◽  
Bond Cleavage ◽  
Synthesis Process ◽  
Strong Electron ◽  
Mild Conditions ◽  
Ru Nanoparticles ◽  
Rate Determining Step ◽  
Highly Active ◽  
Composite Oxides ◽  
Low Crystalline

<p>To mitigate global problems related to energy and global warming, it is helpful to develop an ammonia synthesis process using catalysts that are highly active under mild conditions. Here we show that the ammonia synthesis activity of Ru/Ba/LaCeO<i><sub>x</sub></i> pre-reduced at 700 °C is the highest reported among oxide-supported Ru catalysts. Our results indicate that low crystalline oxygen-deficient composite oxides, which include Ba<sup>2+</sup>, Ce<sup>3+</sup> and La<sup>3+</sup>, with strong electron-donating ability, accumulate on Ru particles and thus promote N≡N bond cleavage, which is the rate determining step for ammonia synthesis.</p>

1H and 13C NMR spectra of 2,2’-disubstitutedtrans-azobenzenes suitable for preparation of metallized azo dyes

1991 ◽  
Vol 56 (10) ◽  
pp. 2160-2168 ◽  
Author(s):  
Josef Jirman
Keyword(s):  
Nmr Spectra ◽  
Electron Pair ◽  
Phenyl Group ◽  
Aprotic Solvents ◽  
1H And 13C Nmr ◽  
Predominant Form ◽  
Rapid Equilibrium ◽  
Dipolar Aprotic Solvents ◽  
Free Electron Pair ◽  
C Nmr

The 1H and 13C NMR spectra have been measured of six trans-azobenzenes substituted at 2 and 2’ positions with substituents favourable for complex formation with a metal (OH, NH2, NHCOCH3, COOH). From the standpoint of NMR such substituted trans-azobenzenes are present in solution in a rapid equilibrium following from rotation around the bond between C-1 of phenyl group and N atom of azo linkage. The predominant form has the substituent in the syn-position with respect to the free electron pair of the nearer azo nitrogen atom. The equilibrium is affected by dipolar aprotic solvents (such as hexadeuteriodimethyl sulfoxide) by decreasing the presence of the predominant form by 1 to 11%.

Trioxorhenium as a strong acceptor group: ab initio CI investigations on the Re-L bonding in L-ReO3 complexes (L = C5H5, CH3, Cl, F, CF3)

1992 ◽  
Vol 96 (26) ◽  
pp. 10800-10804 ◽  
Author(s):  
Roland Wiest ◽  
Thierry Leininger ◽  
Gwang Hi Jeung ◽  
Marc Benard
Keyword(s):  
Ab Initio ◽  
Acceptor Group
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