Substituent Effects on the Benzene Ring. Determination of the Intramolecular Interactions of Substituents intert-Alkyl-Substituted Catechols from Thermochemical Measurements

2000 ◽  
Vol 45 (5) ◽  
pp. 946-952 ◽  
Author(s):  
Sergey P. Verevkin ◽  
Christoph Schick
Keyword(s):  
Benzene Ring ◽  
Substituent Effects ◽  
Intramolecular Interactions

scholarly journals Fluorescent Orthopalladated Complexes of 4-Aryliden-5(4H)-Oxazolones from the Kaede Protein: Synthesis and Characterization

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1238
Author(s):  
Eduardo Laga ◽  
David Dalmau ◽  
Sofía Arregui ◽  
Olga Crespo ◽  
Ana I. Jimenez ◽  
...  
Keyword(s):  
Intramolecular Interactions ◽  
Ortho Position ◽  
Fluorescent Properties ◽  
Ancillary Ligands ◽  
X Ray ◽  
Mononuclear Complexes ◽  
Fluorescence Measurements ◽  
Anionic Ligands ◽  
Order Of Magnitude

The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4H)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the ortho carbon of the arylidene ring. Two different 4-((Z)-arylidene)-2-((E)-styryl)-5(4H)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring (1a OMe; 1b F), were used as starting materials. Oxazolones 1a and 1b were reacted with Pd(OAc)2 to give the corresponding dinuclear orthometalated palladium derivates 2a and 2b by regioselective C–H activation of the ortho-position of the arylidene ring. Reaction of 2a (2b) with LiCl promoted the metathesis of the bridging carboxylate by chloride ligands to afford dinuclear 3a (3b). Mononuclear complexes containing the orthopalladated oxazolone and a variety of ancillary ligands (acetylacetonate (4a, 4b), hydroxyquinolinate (5a), aminoquinoline (6a), bipyridine (7a), phenanthroline (8a)) were prepared from 3a or 3b through metathesis of anionic ligands or substitution of neutral weakly bonded ligands. All species were fully characterized and the X-ray determination of the molecular structure of 7a was carried out. This structure has strongly distorted ligands due to intramolecular interactions. Fluorescence measurements showed an increase in the quantum yield (QY) by up to one order of magnitude on comparing the free oxazolone (QY < 1%) with the palladated oxazolone (QY = 12% for 6a). This fact shows that the coordination of the oxazolone to the palladium efficiently suppresses the hula-twist deactivation pathway.

Substituent effects of mono-, bis-, and tris(trimethylsilyl)methyl groups; determination of σ− and σ+-constants

1970 ◽  
Vol 24 (2) ◽  
pp. 293-299 ◽  
Author(s):  
M.A. Cook ◽  
C. Eaborn ◽  
D.R.M. Walton
Keyword(s):  
Substituent Effects ◽  
Methyl Groups

4-Substituted quinuclidinium perchlorates in the determination of polar substituent effects

1973 ◽  
Vol 14 (37) ◽  
pp. 3627-3630 ◽  
Author(s):  
E. Ceppi ◽  
W. Eckhardt ◽  
C.A. Grob
Keyword(s):  
Substituent Effects ◽  
Polar Substituent

Determination of substituent effects on the proton affinities of natural nucleosides by the kinetic method

2021 ◽  
Vol 56 (1) ◽  
Author(s):  
Angelo Liguori ◽  
Anna Napoli ◽  
Giovanni Sindona
Keyword(s):  
Kinetic Method ◽  
Substituent Effects ◽  
Proton Affinities

2-Anilino-1.3.4-thiadiazole, Hemmstoffe der oxidativen und photosynthetischen Phosphorylierung

1975 ◽  
Vol 30 (3-4) ◽  
pp. 183-189 ◽  
Author(s):  
G. Schäfer ◽  
A. Trebst ◽  
K. H. Büchel
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Oxidative Phosphorylation ◽  
Benzene Ring ◽  
Inhibitory Action ◽  
Substituent Effects ◽  
Photosynthetic Electron Transport ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Oxidative Phosphorylation

Abstract 2-anilino-1,3,4-thiadiazoles carrying various substituents in the 5-position as well as in the benzene-ring were synthesized. The compounds were tested with rat-liver-mitochondria and with spinach-chloroplasts and revealed to be potent uncouplers of both, oxidative and photosynthetic phosphorylation, with p I50-values rangeing from 6.79 to 4.05. At higher concentration all compounds are inhibitors of the Hillreaction. In mitochondria a fair correlation exists between pKa of the acidic NH-group and the uncoupling activity; a maximum is obtained around pKa= 6 .8 , whereas in chloroplasts activity is shifted to more acid pKa-values. The compounds meet the requirements for uncouplers according to the chemi-osmotic theory, being lipophilic weak acids. N-methylation causes total loss of activity in mitochondrial oxidative phosphorylation. The inhibitory action on photosynthetic electron transport is located within photosystem II. This latter activity is almost independent of substituent effects in contrast to uncoupling of either respiratory- or photo-phosphorylation

Analysis of substituent and solvent effects on dissociation of N-phenylbenzenesulphonamides

1987 ◽  
Vol 52 (12) ◽  
pp. 2900-2908 ◽  
Author(s):  
Miroslav Ludwig ◽  
Oldřich Pytela ◽  
Helena Javůrková ◽  
Miroslav Večeřa
Keyword(s):  
Factor Analysis ◽  
Hydrogen Bonds ◽  
Model Equation ◽  
Substituent Effects ◽  
Regression Function ◽  
Reaction Centre ◽  
Solvent Dependence ◽  
Substituent Constants ◽  
Reaction Constants

The potentiometric titration in water, methanol, dimethyl sulphoxide, dimethylformamide, and acetonitrile has been used for determination of pK values of 13 N-arylbenzenesulphonamides. The validity of the Hammett and Yukawa-Tsuno models using several sets of substituent constants has been evaluated by the test to check adequacy of the regression function and by the factor analysis. It has been found that the substituent effects in solvents must be interpreted with regard to the experimental method used, solvent, set of the substituent constants, as well as the model equation ETR. The dependence of the Hammett reaction constants on the solvent has been analyzed and reveals a preferred stabilization of the conjugated base through hydrogen bonds. Direct conjugation of the reaction centre with the substituent and with different extent of the solvent-dependence with the 4-CN and 4-NO2 derivatives have been observed.

Substituent Effects of Phosphorus and Arsenic Containing Groups in Aromatic Substitution. IV. Nitration of Aromatic Phosphine Oxides

1975 ◽  
Vol 53 (10) ◽  
pp. 1468-1474 ◽  
Author(s):  
Edmund Malinski ◽  
Antonina Piekos ◽  
Tomasz A. Modro
Keyword(s):  
Sulfuric Acid ◽  
Benzene Ring ◽  
Phosphorus Atom ◽  
Substituent Effects ◽  
Ortho Position ◽  
Phosphine Oxides ◽  
Aromatic Substitution ◽  
Tertiary Phosphine ◽  
Aqueous Sulfuric Acid

The nitration of some tertiary phosphine oxides ArP(O)R2 in aqueous sulfuric acid has been investigated. All compounds studied react as conjugate acids. When the phosphinyl group is bonded directly to the benzene ring, high deactivation and meta-orientation is found, accompanied in most cases by some substitution at the ortho position. The substituent effects of the "quasiphosphonium" group P(OH)R2+are compared with those of structurally related systems and are discussed in terms of pπ–dπ, interactions of the oxygen and the phosphorus atom.

4-Substituted Quinuclidinium Perchlorates as Models for the Determination of Polar Substituent Effects

1973 ◽  
Vol 12 (4) ◽  
pp. 319-319 ◽  
Author(s):  
Cyril A. Grob ◽  
Werner Simon ◽  
Dieter Treffert
Keyword(s):  
Substituent Effects ◽  
Polar Substituent

Accurate Determination of the Deformation of the Benzene Ring upon Substitution: Equilibrium Structures of Benzonitrile and Phenylacetylene

2013 ◽  
Vol 117 (48) ◽  
pp. 12969-12982 ◽  
Author(s):  
Heinz Dieter Rudolph ◽  
Jean Demaison ◽  
Attila G. Császár
Keyword(s):  
Benzene Ring ◽  
Accurate Determination ◽  
Equilibrium Structures
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