Mechano-isomerization of azobenzene

Surampudi, Sravan K.; Patel, Harik R.; Gavvalapalli, Nagarjuna; Venkataraman, D.

doi:10.1039/c3cc43797c

Cited by 30 publications

(37 citation statements)

References 22 publications

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“…A strong relationship between rate of reactions and solvent polarity points to an intermediate transition state that is considerably more polar than the cis conformation. This polar transition state is indicative of a rotational mechanism for the isomerization of 4A4NAB [21,22,24]. This result is expected considering the strong electron withdrawing group (the nitro group) on 4A4NAB and is corroborated by computational studies [22,25,26].…”

supporting

confidence: 70%

The Kinetics of the Cis-to-Trans Thermal Isomerization of 4-Anilino-4’- Nitroazobenzene are Highly Influenced by Solvent Polarity

Smith¹,

Bou-Abdallah²

2017

J Thermodyn Catal

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supporting

confidence: 70%

The Kinetics of the Cis-to-Trans Thermal Isomerization of 4-Anilino-4’- Nitroazobenzene are Highly Influenced by Solvent Polarity

Smith¹,

Bou-Abdallah²

2017

J Thermodyn Catal

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“… 34 claimed that mechanoisomerization of azobenzene typically results in the cleavage of the N=N azo bond. However, more recent theoretical calculations 35 and experiments 36 have challenged this view.…”

Section: Resultsmentioning

confidence: 99%

“…2b . Previous studies 36 37 on the trans -to- cis isomerization of azobenzene in the presence of UV light showed that the reaction follows first-order kinetics and the rate constant k can be written as follows:…”

Section: Resultsmentioning

confidence: 99%

Light-enhanced liquid-phase exfoliation and current photoswitching in graphene–azobenzene composites

et al. 2016

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Multifunctional materials can be engineered by combining multiple chemical components, each conferring a well-defined function to the ensemble. Graphene is at the centre of an ever-growing research effort due to its combination of unique properties. Here we show that the large conformational change associated with the trans–cis photochemical isomerization of alkyl-substituted azobenzenes can be used to improve the efficiency of liquid-phase exfoliation of graphite, with the photochromic molecules acting as dispersion-stabilizing agents. We also demonstrate reversible photo-modulated current in two-terminal devices based on graphene–azobenzene composites. We assign this tuneable electrical characteristics to the intercalation of the azobenzene between adjacent graphene layers and the resulting increase in the interlayer distance on (photo)switching from the linear trans-form to the bulky cis-form of the photochromes. These findings pave the way to the development of new optically controlled memories for light-assisted programming and high-sensitive photosensors.

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“…Only recently, after studies of the molecular physics of the photoisomerization of azo dyes have revealed that the photoisomerization reaction occurs on the timescale of a few picoseconds (2,3), azobenzenes came back into focus as potential photoswitchable materials (4,5). Azobenzenes have been investigated in terms of ultrafast spectroscopy (4, 6, 7), mechanoisomerization (8), the effect of slow photons (9), two-photon absorption (10) and laser-induced periodic surface structuring (11)(12)(13)(14)(15)(16)(17). The latter describes the phenomenon of Turing pattern formation on the surface of an azopolymer film upon exposure to UV or visible light.…”

mentioning

confidence: 99%

Instability-induced pattern formation of photoactivated functional polymers

Galinski

Ambrosio

Maddalena

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Since the pioneering work of Turing on the formation principles of animal coat patterns [Turing AM (1952) Phil Trans R Soc Lond B 237(641):37-72], such as the stripes of a tiger, great effort has been made to understand and explain various phenomena of selfassembly and pattern formation. Prominent examples are the spontaneous demixing in emulsions, such as mixtures of water and oil [Herzig EM, et al. (2007) Nat Mater 6:966-971]; the distribution of matter in the universe [Kibble TWB (1976 A zobenzenes, which belong to photochromic materials, are switchable two-state systems with distinct optical, electronic, magnetic, and/or electrochemical properties that can be reversibly converted by irradiation. Since the discovery of the unique photochemical properties of azobenzene in 1937 (1), azobenzenes have been mainly used in the chemical industry. Only recently, after studies of the molecular physics of the photoisomerization of azo dyes have revealed that the photoisomerization reaction occurs on the timescale of a few picoseconds (2, 3), azobenzenes came back into focus as potential photoswitchable materials (4, 5). Azobenzenes have been investigated in terms of ultrafast spectroscopy (4, 6, 7), mechanoisomerization (8), the effect of slow photons (9), two-photon absorption (10) and laser-induced periodic surface structuring (11-17). The latter describes the phenomenon of Turing pattern formation on the surface of an azopolymer film upon exposure to UV or visible light. The outstanding feature of this photoactivated pattern formation is its dependence on both the light's intensity and polarization, which allows for the formation of a large variety of Turing patterns, such as hexagonal cells, parallel stripes, or turbulent structures. Several attempts have been made to understand the underlying physics that controls these various forms of pattern formation (18-23), but a sound picture is still lacking.In this paper, we demonstrate that the photoactivated pattern formation on azopolymer films can be entirely explained by the physical concept of phase separation of two coexistent immiscible phases in the polymer. A phase separation can be briefly characterized as follows: A (meta)stable configuration subjected to an external perturbation (temperature, light) becomes unstable. The unstable system tends to equilibrate by the formation of two immiscible phases. These two phases tend to separate leading to a spatial reorganization of the system.In the case of azopolymers, the instability is caused by the random optical excitation of the isomers in the polymer film. Excited by a photon of suitable energy (λ = 200-550 nm), the azobenzene isomer undergoes a structural transition by inversion or rotation (3), called photoisomerization, and relaxes either in the trans or cis ground state. The symmetry of the system is broken. The principle of the photoisomerization reaction for one azobenzene isomer is illustrated in Fig. 1A. The ground-state energy is characterized by an asymmetric double-well potential (Fig. 1A), containing...

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Mechano-isomerization of azobenzene

Cited by 30 publications

References 22 publications

The Kinetics of the Cis-to-Trans Thermal Isomerization of 4-Anilino-4’- Nitroazobenzene are Highly Influenced by Solvent Polarity

The Kinetics of the Cis-to-Trans Thermal Isomerization of 4-Anilino-4’- Nitroazobenzene are Highly Influenced by Solvent Polarity

Light-enhanced liquid-phase exfoliation and current photoswitching in graphene–azobenzene composites

Instability-induced pattern formation of photoactivated functional polymers

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