Folded Conformations. IV. Intramolecular Shielding and Intramolecular Charge-Transfer Interaction in Benzyl Phenyl Sulfones and Sulfoxides

1973 ◽  
Vol 51 (8) ◽  
pp. 1187-1191 ◽  
Author(s):  
(Mrs.) Renée van Est-Stammer ◽  
Jan B. F. N. Engberts
Keyword(s):  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Charge Transfer Band ◽  
Alkyl Substituent ◽  
Aromatic Proton ◽  
Electron System ◽  
High Electron ◽  
Aromatic Rings ◽  
Proton Resonances ◽  
Repulsive Forces

Proton magnetic resonance spectra of the title compounds (A-SO2CHR-D) were measured and compared with the spectra of appropriate reference systems containing an alkyl substituent instead of one of the aromatic rings. The observed upfield shifts of the aromatic proton resonances in the title compounds suggest that there is a significant population of folded conformations, which possess a gauche orientation of the aromatic rings. This conclusion is supported by the observation of an intramolecular charge-transfer band in the u.v. spectra of the compounds containing an A ring of high electron affinity and a D ring of low ionization potential. Stabilization of the folded forms may be obtained through minimizing the n–π repulsive forces between the sulfonyl oxygen lone pairs and the π-electron system of the D ring.

INTRAMOLECULAR CHARGE-TRANSFER INTERACTION BETWEEN LONE PAIR ELECTRONS AND π-ELECTRON SYSTEM

1977 ◽  
Vol 6 (9) ◽  
pp. 1047-1050 ◽  
Author(s):  
Kiyoshi Mutai ◽  
Keiji Kobayashi ◽  
Tsunetoshi Kobayashi ◽  
Chikatoshi Utsunomiya
Keyword(s):  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Lone Pair ◽  
Electron System ◽  
Charge Transfer Interaction ◽  
Lone Pair Electrons

Photophysical, electrochemical, and spectroelectrochemical investigation of electronic push–pull benzothiadiazole fluorophores

2015 ◽  
Vol 87 (7) ◽  
pp. 649-661 ◽  
Author(s):  
Monika Wałęsa-Chorab ◽  
Marie-Hélène Tremblay ◽  
Mohamed Ettaoussi ◽  
William G. Skene
Keyword(s):  
Thin Films ◽  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Charge Transfer Band ◽  
Aprotic Solvents ◽  
Neutral Form ◽  
Electron Withdrawing Group ◽  
Fluorescence Wavelength ◽  
Stokes Shifts ◽  
Spectroelectrochemical Properties

AbstractTwo electronic push–pull fluorophores consisting of a benzothiadiazole core and a terminal N,N-dimethylamino electron donating group were prepared. The effect of the terminal electron withdrawing group (–NO2 and –CN) on the spectroscopic, electrochemical, and spectroelectrochemical properties were examined. The fluorophores were solvatochromic with Stokes shifts upward of 9000 cm−1 being observed in aprotic solvents of varying polarity. It was found that the fluorophores fluoresced appreciably (86 % > Φfl > 18 %) in hexane, toluene, diethyl ether, dichloromethane, ethyl acetate, and THF. The fluorescence was quenched in acetonitrile, acetone, and DMSO. The fluorophores also fluoresced appreciably in thin films when embedded in poly(methyl methacrylate) and poly(dimethylsiloxane) matrices. Protonating the terminal amine with trifluoroacetic acid quenched the intramolecular charge transfer band, although the fluorophores remained fluorescent. The fluorophores could also be reversibly oxidized electrochemically. The resulting oxidized state was visually different than the neutral form. Electrochemical oxidation also led to reversible changes in both the fluorescence wavelength and intensity.

Effects of lignin structure and solvent on the formation rate of quinone methide under alkaline conditions

Holzforschung ◽  
2020 ◽  
Vol 74 (6) ◽  
pp. 559-566
Author(s):  
Fuyu Yamauchi ◽  
Toko Ito ◽  
Osamu Kawamoto ◽  
Toshihiro Komatsu ◽  
Takuya Akiyama ◽  
...  
Keyword(s):  
Formation Rate ◽  
Alkyl Substituent ◽  
Electron System ◽  
Chain Structure ◽  
Quinone Methide ◽  
High Electron ◽  
Initial State ◽  
Lignin Model Compound ◽  
Rate Determining Step ◽  
Alkaline Conditions

AbstractThe purpose of this study was to examine how differences in the type of aromatic nucleus, side-chain structure and type of solvent affect the formation rate of quinone methide (QM) in the alkaline reaction of lignin. The reaction was done at a NaOH concentration of 1.0 mol l−1 and temperature of 75–140°C under an anaerobic condition. The formation rates of QM were in the order: syringyl > guaiacyl > p-hydroxyphenyl, when model compounds with lignin-type aromatic nuclei were compared. This and other results on various phenolic compounds suggested that the formation of QM is rapid from compounds having a high electron density in the aromatic π-electron system. The formation of QM was faster from a C6-C2-type than from a C6-C1-type lignin model compound, which was attributed to the fact that QM is an alkene and hence more stable when an unsaturated carbon in QM has an alkyl substituent, like the C6-C2-type compound. When aqueous 1,4-dioxane solutions with different 1,4-dioxane contents were used, the formation of QM became slower with increasing 1,4-dioxane content. This can be explained by the variation in the negative charge density in the rate-determining step, where the density is larger at the transition than at the initial state and consequently the activation energy is lower in a solvent with higher polarity.

Combining High Electron Affinity and Intramolecular Charge Transfer in 1,3-Dithiole–Nitrofluorene Push–Pull Diads

2008 ◽  
Vol 14 (9) ◽  
pp. 2757-2770 ◽  
Author(s):  
Dmitrii F. Perepichka ◽  
Igor F. Perepichka ◽  
Oleksandr Ivasenko ◽  
Adrian J. Moore ◽  
Martin R. Bryce ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Electron Affinity ◽  
Intramolecular Charge Transfer ◽  
High Electron ◽  
High Electron Affinity

Solvatochromism and solvatofluorochromism of the intramolecular charge transfer band of 4-dimethylaminochalcone in the electronic spectra of its solutions

2006 ◽  
Vol 100 (5) ◽  
pp. 700-708 ◽  
Author(s):  
N. G. Bakhshiev ◽  
S. K. Gularyan ◽  
G. E. Dobretsov ◽  
A. Yu. Kirillova ◽  
V. Yu. Svetlichnyĭ
Keyword(s):  
Charge Transfer ◽  
Electronic Spectra ◽  
Intramolecular Charge Transfer ◽  
Charge Transfer Band

Dynamic adjustment of emission from both singlets and triplets: the role of excited state conformation relaxation and charge transfer in phenothiazine derivates

2021 ◽  
Author(s):  
Weidong Qiu ◽  
Xinyi Cai ◽  
Mengke Li ◽  
Liangying Wang ◽  
Yanmei He ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Intramolecular Charge Transfer ◽  
Dynamic Adjustment ◽  
Twisted Intramolecular Charge Transfer

Dynamic adjustment of emission behaviours by controlling the extent of twisted intramolecular charge transfer character in excited state.

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