Photo-induced Inversion of the Cholesteric Helix in Systems Containing 3(<i>R</i>)-Methylcyclohexanone 6-Arylidene Derivatives

Krivoshey, Alexander I.; Shkolnikova, N. I.; Pivnenko, N. S.; Kutulya, L. A.

doi:10.1080/15421400600580055

Cited by 4 publications

(2 citation statements)

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“…A number of photochromes such as azobenzene, [28–38] diarylethene, [39,40] sterically overcrowded alkene, [41–43] spirooxazine, [44] fulgide, [45] unsaturated ketone [46–48] and naphthopyran [49] were used as chiral dopants with photoisomerization ability. Two large reviews devoted to the photoalignment of polymer CLCs and the creation of photocontrollable materials have been published by two of our coauthors [50,51] …”

Section: Introductionmentioning

confidence: 99%

“…[27] Alternating irradiation of the relief surface with blue and green light leads to twisting-untwisting transformation of the helix, which makes it possible to organize the movement of particles along the changing surface. [26] A number of photochromes such as azobenzene, [28][29][30][31][32][33][34][35][36][37][38] diarylethene, [39,40] sterically overcrowded alkene, [41][42][43] spirooxazine, [44] fulgide, [45] unsaturated ketone [46][47][48] and naphthopyran [49] were used as chiral dopants with photoisomerization ability. Two large reviews devoted to the photoalignment of polymer CLCs and the creation of photocontrollable materials have been published by two of our coauthors.…”

Section: Introductionmentioning

confidence: 99%

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Large Thermally Irreversible Photoinduced Shift of Selective Light Reflection in Hydrazone‐Containing Cholesteric Polymer Systems

et al. 2023

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Stimuli responsive liquid crystalline polymers are a unique class of so‐called “smart” materials demonstrating various types of mesomorphic structures easily controlled by external fields, including light. In the present work we synthesized and studied a comb‐shaped hydrazone‐containing copolyacrylate exhibited cholesteric liquid crystalline properties with the pitch length of the helix being tuned under irradiation with light. In the cholesteric phase selective light reflection in the near IR spectral range (1650 nm) was measured and a large blue shift of the reflection peak from 1650 nm to 500 nm was found under blue light (428 or 457 nm) irradiation. This shift is related to the Z‐E isomerization of photochromic hydrazone‐containing groups and it is photochemically reversible. The improved and faster photo‐optical response was found after copolymer doping with 10 wt % of low‐molar‐mass liquid crystal. It is noteworthy that both, the E and Z isomers of hydrazone photochromic group are thermally stable that enable to achieve a pure photoinduced switch without any dark relaxation at any temperatures. The large photoinduced shift of the selective light reflection, together with thermal bistability, makes such systems promising for applications in photonics.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Large Thermally Irreversible Photoinduced Shift of Selective Light Reflection in Hydrazone‐Containing Cholesteric Polymer Systems

et al. 2023

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Structure of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone as chiral component of liquid-crystalline systems

et al. 2006

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The spatial structure of (Z ) (5R) methyl 2 (4 phenylbenzylidene)cyclohexanone prepared by photochemical isomerization of the E isomer was studied by analyzing the magnitudes and temperature dependence of the proton spin spin coupling constants obtained by 1 H NMR spectroscopy and the results of molecular modeling using semiempirical quantum chemical AM1 and PM3 methods and the density functional theory (DFT). Comparison of the results obtained for the Z and E isomers shows that in both cases the conformational equilibrium for both isomers is characterized by significant preference of the chair conformer having an equatorial methyl group, namely, -∆H (chair a chair e) = 1.98-2.12 and 1.36-1.54 kcal mole -1 for the Z and E isomers, respectively. Distinctions in the non planar ity of the enone fragment and cyclohexanone ring in the Z and E isomers under study following from the results of mathematical modeling were confirmed by the experimental values of the geminal spin spin coupling constants of protons of the methylene groups in α,α´ positions with respect to the enone group. Quantum chemical calculations of the Z isomer revealed the existence of intramolecular hydrogen bond between the carbonyl oxygen and the nearest aromatic proton in ortho position of the benzene ring. Possible reasons for different helical twisting power of (Z ) (5R) methyl 2 (4 phenylbenzylidene)cyclohexanone and the E and Z arylidene derivatives of 1R,4R isomenthone in the mesophase are discussed based on the results of molecular structure studies for these compounds.Key words: (Z ) and (E) (5R) methyl 2 (4 phenylbenzylidene)cyclohexanone, confor mational state, 1 H NMR spectroscopy, quantum chemical calculations, intramolecular hydro gen bond. Chiral α,β unsaturated ketones with six membered ring preset s cis configuration of enone fragment and a Z or E configuration relative to the double bond are of considerable interest as components of liquid crystalline (LC) systems with induced helical supramolecular order ing. 1-4 Photoinduced effects in LC compositions, which accompany a reversible photochemical E-Z isomeriza tion typical of these compounds, 5-9 strongly depend on the nature of both the nematic solvent and, especially, the chiral additive (CA), although the reasons for this depen dence are unclear.Photoactive CA include, in particular, 2 arylidene de rivatives of (1R,4R) isomenthone ((3R,6R) 6 isopropyl 3 methylcyclohexanone) 1*, which were studied in detail earlier. 5,6,10,11 UV Irradiation of E isomers in both iso tropic organic solvents 5,10 and LC media 5,11 causes a highly efficient E-Z photoisomerization. A feature of this photochemical transformation consists in a higher quan tum yield of the direct reaction compared to that of the reverse reaction. This predetermines a much higher pro portion of the Z isomer in the photostationary state. 10 An important macroscopic manifestation of this photo transformation in doped LC compositions is an increase in the pitch of the supramolecular helix (P), i.e., its un twisting. 5,11 A n...

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New steroid α,β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

et al. 2009

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Photo-induced Inversion of the Cholesteric Helix in Systems Containing 3(R)-Methylcyclohexanone 6-Arylidene Derivatives

Cited by 4 publications

References 14 publications

Large Thermally Irreversible Photoinduced Shift of Selective Light Reflection in Hydrazone‐Containing Cholesteric Polymer Systems

Large Thermally Irreversible Photoinduced Shift of Selective Light Reflection in Hydrazone‐Containing Cholesteric Polymer Systems

Structure of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone as chiral component of liquid-crystalline systems

New steroid α,β-unsaturated ketones as chiral components of induced cholesteric liquid crystal systems

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