Photo orientation of azo dye molecules in glassy o-terphenyl

Grebenkin, S. Yu.; Большаков, Б. В.

doi:10.1016/j.jphotochem.2006.04.009

Cited by 12 publications

(15 citation statements)

References 26 publications

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“…It is for this reason that the photoorientation of A CN (proportional to the difference between A p and A s ) continues to grow at a slow rate and never saturates over the time scale of the experiment (Figure ). An increase in A s after the rapid AHB was also reported using UV–vis spectroscopy for cyano-tailed azobenzenes covalently bonded as side chains to polyurethane and for 1-naphthylazomethoxybenzene in glassy o -terphenyl . The fact that A s increases under irradiation after the rapid initial AHB supports the conclusion that the slow process of photoorientation is due to the AR of the trans conformers toward the direction perpendicular to the laser polarization and is not due to AHB or to photobleaching.…”

Section: Resultssupporting

confidence: 64%

“…An increase in A s after the rapid AHB was also reported using UV− vis spectroscopy for cyano-tailed azobenzenes covalently bonded as side chains to polyurethane 71 and for 1-naphthylazomethoxybenzene in glassy o-terphenyl. 72 The fact that A s increases under irradiation after the rapid initial AHB supports the conclusion that the slow process of photoorientation is due to the AR of the trans conformers toward the direction perpendicular to the laser polarization and is not due to AHB or to photobleaching. It can also be observed from Figure 7b (and Figure S7a for additional F A ) that the relative importance of the fast AHB and slow AR processes depends on the degree of complexation of P4VP/A CN , with AR contributing more strongly at high F A .…”

Section: ■ Results and Discussionmentioning

confidence: 58%

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Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

et al. 2018

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To optimize azobenzene-containing materials for applications such as rewritable waveguides and holographic data storage, it is imperative to understand the effect of the azobenzene structure on the photoresponse of the material. Supramolecular materials, in which a complexed photoactive azobenzene controls the motion or other properties of a passive polymer, are uniquely convenient for studying the impact of specific chemical modifications. Here, we use polarization modulation infrared structural absorbance spectroscopy (PM-IRSAS) to hydrogen-bonded supramolecular azobenzene complexes using poly(4-vinylpyridine) (P4VP) as a model polymer. We show that changing the tail group from hydrogen (AH) to cyano (ACN) induces greater angular redistribution of the chromophores and, remarkably, provokes P4VP pyridine ring orientation. Increasing the degree of complexation decreases the saturated orientation of both AH and ACN, whereas for P4VP/ACN it increases the pyridine orientation as well as the orientation stability of both components. These results explain the contrasting photoinduced birefringence behavior previously observed for these complexes and identify azo-azo intermolecular interactions as the main reason. To our knowledge, this is the first molecular-level spectroscopic analysis of the contrasting contributions of azobenzenes to the photo-orientation of supramolecular azopolymer complexes and the first report of the large impact of small molecular changes on the capacity of azo dyes to transfer light-induced orientation to a photopassive polymer. 29 bonds. In many cases, the passive polymer host employed is poly(4-vinylpyridine) (P4VP). [16][17][18][19][20][21][23][24][25][26][27][28][29] Various studies have revealed that the chemical structure and the content of the supramolecularly attached azo have significant impact on the measured PIB [23][24][25]30 and on SRG formation efficiency. [20][21][22] For example, the saturated PIB per azobenzene unit of hydrogen-bonded P4VP-azo complexes, where the azos used differ only by the nature of its tail group (Scheme 1), increases by more than a factor of 2 when increasing azo content for the cyano-tailed azo (CN-tailed or ACN), whereas it decreases by up to a factor of 2 for the hydrogen-tailed azo (H-tailed or AH). 25

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Section: Resultssupporting

confidence: 64%

Section: ■ Results and Discussionmentioning

confidence: 58%

Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

et al. 2018

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“…This value of dichroism is more than two times lower than the maximum value obtained for azobenzene-containing side-chain polymers (∼0.7) [15], but, nevertheless, is much higher than that reported before for glassy amorphous low-molar mass compounds [31][32][33]. The relatively low values of the dichroism in comparison with the azobenzenecontaining polymers can be explained by the presence of bent-shaped fragments that decrease the uniaxial orientation and anisotropy.…”

Section: Results Of the Photochemical Studiescontrasting

confidence: 56%

“…Only a few papers consider photo-orientation processes in lowmolar mass amorphous glassy compounds [31][32][33]. It has been demonstrated that in these systems only small values of photo-induced order parameter and dichroism were achieved (∼0.004), which are much smaller than those for the azobenzene-containing LC polymers (in the range of 0.3-0.7 ).…”

Section: Introductionmentioning

confidence: 99%

Photochromic azobenzene functionalised banana–calamitic dimers and trimers: mesophase behaviour and photo-orientational phenomena

et al. 2011

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Azobenzene functionalised banana-calamitic dimers and a novel type of banana-calamitic-banana trimers have been synthesised. Their thermotropic behaviour and the structure of the mesophases have been characterised by differential scanning calorimetry, polarising optical microscopy and X-ray diffractions measurements. Electro-optical studies evidence the polar properties of the smectic phases. A rare anticlinic-synclinic smectic CP (SmCP) phase transition could be proven for two of the twins upon cooling without an electric field although the molecules are not optically active. Remarkably, the phase sequence SmC a -SmC s has been observed upon cooling, the inverse sequence to that reported for non-chiral compounds up to now. A comparative study of the photochemical properties of dilute solutions and of thin films of two compounds has been performed. Irradiation with polarised ultra-violet (365 nm) and visible light (473 nm) induces a photo-orientation process of the chromophores in a direction perpendicular to the polarisation plane of the exciting light. For a trimeric compound bearing an azobenzene bridge between both bent-core mesogenic units this process is associated with cycles of the E-Z-E isomerisation of the azobenzene groups followed by rotational diffusion of molecules in the films. For a bis(azobenzene) containing dimer the E-Z isomerisation in films is strongly suppressed and the photo-induced orientation has a rotational diffusion mechanism.

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“…[1], [2] In particular, applications of sterically demanding ortho-terphenyls span from synthetic pharmaceuticals [3] over key structures in organic light-emitting diodes (OLEDs) [4] to matrixes for photoinduced formation of optical absorption anisotropy. [5] Nonetheless, synthesis of ortho-terphenyls remains challenging due to steric hindrance of two ortho-standing aromatic rings. Existing synthetic routes towards ortho-terphenyls include Diels-Alder reactions followed by aromatization [6] or Ullman-coupling.…”

Section: Introductionmentioning

confidence: 99%

Facile Access to Challenging ortho‐Terphenyls via Merging Two Multi‐Step Domino Reactions in One‐Pot: A Joint Experimental/Theoretical Study

et al. 2019

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ortho‐Terphenyls are of high interest for medicinal chemistry and materials science, but they are difficult to access. Herein, we demonstrate a straightforward and sustainable synthesis of highly functionalized ortho‐terphenyls via joining an organocatalyzed two‐step domino reaction (Knoevenagel/vinylogous Michael) with a DABCO/CuBr2 co‐catalyzed three‐step domino reaction (cyclization/tautomerization/aromatization) in a one‐pot process. Overcoming necessity to isolate intermediate products leads to a reduction of energy, costs and waste for a broad scope of reactions. DFT calculations have been performed to investigate the thermodynamics of this one‐pot process towards ortho‐terphenyls and to study the reaction profile of the vinylogous Michael reaction under inclusion of solvent effects. Role of London dispersion forces in this transformation has been elucidated. It is shown that reaction kinetics and thermodynamics are slightly influenced by dispersion interactions. Furthermore, the addition of dispersion energy donors leads to small changes of reaction energies in some cases.

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Photo orientation of azo dye molecules in glassy o-terphenyl

Cited by 12 publications

References 26 publications

Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

Photochromic azobenzene functionalised banana–calamitic dimers and trimers: mesophase behaviour and photo-orientational phenomena

Facile Access to Challenging ortho‐Terphenyls via Merging Two Multi‐Step Domino Reactions in One‐Pot: A Joint Experimental/Theoretical Study

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