Quantification of the push–pull character of azo dyes and a basis for their evaluation as potential nonlinear optical materials

Kleinpeter, Erich; Bölke, Ute; Kreicberga, Jana

doi:10.1016/j.tet.2010.04.067

Cited by 29 publications

(14 citation statements)

References 34 publications

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“…Resonance forms related to electron donating "push" of the substituent para to the azo bond. Push-pull effects are widely cited as an important mechanism for understanding how various substituents alter the colour of a dye [39][40][41]. Of importance, here is the idea that an electron donating group para to the azo bond will effectively lengthen the azo bond, Scheme 2, and so give rise to a bathochromatic colour shift.…”

Section: Methodsmentioning

confidence: 99%

Monosulfonated Azo Dyes: A Crystallographic Study of the Molecular Structures of the Free Acid, Anionic and Dianionic Forms

et al. 2020

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Crystallographic studies of monosulfonated azo dyes have concentrated on the salt forms that contain the azo anion. Here we present a study that compares the structures of these anions with protonated free acid forms and with doubly deprotonated dianion forms. To this end, the new single crystal diffraction structures of 13 systematically related free acid forms of monosulfonated azo dyes are presented, together with three new structures of doubly deprotonated forms and two new structures of Na salt forms of azo anions. No structures of dideprotonated monosulfonated azo dyes have previously been reported and this paper also reports the first crystal structure of an azo dye with a hydronium cation. The geometries of the free acid, anion and dianion forms are compared to literature equivalents. It is shown that protonation of the azo bond gives predictable bond lengthening and shortening, which is of a greater magnitude than similar effects caused by azo-hydrazone tautomerisation, or the smaller again effects caused by the resonance electron donation from O or N based substituents. The dianion containing structures have twisted dianion geometries that can be understood based on the resonance effects of the phenoxide groups and upon the needs to bond to a relatively high number of metal cations.

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Section: Methodsmentioning

confidence: 99%

Monosulfonated Azo Dyes: A Crystallographic Study of the Molecular Structures of the Free Acid, Anionic and Dianionic Forms

et al. 2020

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“…These "pseudo-stilbenes" display a strong and broad absorption band in the visible region and the colour exhibited by these chromophores can be controlled by the appropriate choice of substituents. Due to the asymmetric electron distribution they possess important nonlinear optical properties that have been extensively used in designing nonlinear optical materials [1][2][3][4][5]. Among these, heteroaryl azo dyes have recently attracted the attention of many groups due to their diverse optical applications such as second harmonic generation and optical switching [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Photoswitching in azo dyes bearing thienylpyrrole and benzothiazole heterocyclic systems

Coelho¹,

Castro²,

Fonseca³

et al. 2012

Dyes and Pigments

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Visible light promotes the conversion of the E-isomer of benzothiazol-2-yl and benzothiazol-6-yl diazenes to the thermal unstable Z-isomer that reverts in few seconds to the initial form. The kinetics of the thermal Z-E process is strongly influenced by the linkage position of the N=N function to the benzothiazole heterocycle. Thienylpyrrole azo dyes functionalized with benzothiazol-6-yl groups are particularly interesting since they show an excellent compromise between the switching speed (rate constants: 0.068-0.12 s-1) and the amplitude of the absorbance variation (37-42%).

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“…41 From the aforementioned families of compounds, azobenzenes besides interesting applications in the fields of supramolecular organization, 42,43 manipulation of biological systems using light, 44,45 photoorientation of materials and conversion of light into mechanical energy, 46 have also attracted considerable attention in the field of NLO properties due to the high nonlinear response obtained when adding active end groups to the azobenzene core. 25,[47][48][49][50][51][52][53][54] Strangely enough their efficiency in acting as NLO switches has been the subject of only a few investigations 33,37,38,[55][56][57] and it is the major goal of the present contribution to offer a systematic study of NLO properties for this class of molecules.…”

mentioning

confidence: 99%

Designing Efficient Azobenzene and Azothiophene Nonlinear Optical Photochromes

et al. 2014

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International audienceThe present contribution constitutes an extensive density functional theory (DFT) investigation of the nonlinear optical (NLO) properties of a large number of molecules belonging to the azobenzene and azothiophene families of photochromic compounds which can act as NLO switches. Toward the design of systems simultaneously presenting both large total nonlinear response values, beta(tot), and large contrast, beta(ratio), between the cis and trans isomers, we have focused not only on the monomers but also on azobenzene dimers, the latter containing two N=N bonds along the molecular backbone. After it was established that the inclusion of implicit solvation is not important in drawing qualitative conclusions on the NLO switching ability for the investigated systems, gas-phase calculations have shown that for the asymmetric pushpull azobenzene and azothiophene candidates, the combination of strong donating groups such as NPh2, N(Ph-OMe)(2), and N(Ph-NMe2)(2) with the dicyanoethene group CH=C(C=N)(2) as an acceptor delivers large ?trans (150-217 x 10(-30) esu) and non-negligible beta(cis) (18-55 x 10(-30) esu) values as well as substantial contrast, beta(ratio) (3.9-8.7). For the investigated double azobenzenes, it is found that, with a careful choice of donor and acceptor groups, the contrast, beta(ratio), can be significantly increased compared to that of the monomers while maintaining large beta values that facilitate their detection with standard experimental techniques (e.g., electric-field-induced second-harmonic generation). Our results set the stage on which further theoretical and experimental studies can be based in the search for efficient and versatile NLO switches

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Quantification of the push–pull character of azo dyes and a basis for their evaluation as potential nonlinear optical materials

Cited by 29 publications

References 34 publications

Monosulfonated Azo Dyes: A Crystallographic Study of the Molecular Structures of the Free Acid, Anionic and Dianionic Forms

Monosulfonated Azo Dyes: A Crystallographic Study of the Molecular Structures of the Free Acid, Anionic and Dianionic Forms

Photoswitching in azo dyes bearing thienylpyrrole and benzothiazole heterocyclic systems

Designing Efficient Azobenzene and Azothiophene Nonlinear Optical Photochromes

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