Rewritable and switching chiroptical supramolecular nanolayers

Schofield, W. C. E.; Badyal, J. P. S.

doi:10.1039/c2jm14912e

Cited by 3 publications

(4 citation statements)

References 81 publications

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“…521 In this latter study, the authors excluded LD and LB contributions to the measured ECD signals by sample rotation and displacement. Many other azobenzene-functionalized polymethacrylates have been investigated, bearing several enantiopure groups in the side chains as source of chirality: pyrrolidine, 522,523 prolinol, 524 hydroxysuccinimide 525 or (+)-L-lactate 526 bridges, as well as cholesteryl 527 and branched alkyl 528−532 substituents. Most of them revealed a liquid crystal behavior, with a supramolecular order (and chiroptical properties) very sensitive to temperature and light irradiation processes.…”

Section: Ecd In Thin Films Of π-Conjugated Oligomers and Polymersmentioning

confidence: 99%

“…Many other azobenzene-functionalized polymethacrylates have been investigated, bearing several enantiopure groups in the side chains as source of chirality: pyrrolidine, , prolinol, hydroxysuccinimide or (+)- l -lactate bridges, as well as cholesteryl and branched alkyl − substituents. Most of them revealed a liquid crystal behavior, with a supramolecular order (and chiroptical properties) very sensitive to temperature and light irradiation processes. − Furthermore, some examples of achiral polymethacrylates liquid crystals with azobenzene − or azo-binaphthyl chromophores showing induced ECD only after CP-light irradiation were also described; in particular, CP-light-induced supramolecular chirality was also testified via SHG-CD measurements in thin films of the achiral azobenzene polymethacrylate poly(DR1M) .…”

Section: Ecd Properties In Thin Films Of π-Conjugated Systems: Litera...mentioning

confidence: 99%

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Chiroptical Properties in Thin Films of π-Conjugated Systems

2020

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Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecular structures and intermolecular interactions to a large extent. Electronic circular dichroism, ECD, and its emission counterpart, circularly polarized luminescence, CPL, provide tools for studying aggregated states and the key properties to be sought for designing innovative devices. In this review, we shall present a comprehensive coverage of chiroptical properties measured on thin films of organic π-conjugated molecules. In the first part, we shall discuss some general concepts of ECD, CPL, and other chiroptical spectroscopies, with a focus on their applications to thin film samples. In the following, we will overview the existing literature on chiral π-conjugated systems whose thin films have been characterized by ECD and/or CPL, as well other chiroptical spectroscopies. Special emphasis will be put on systems with large dissymmetry factors (g abs and g lum) and on the application of ECD and CPL to derive structural information on aggregated states.

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Section: Ecd In Thin Films Of π-Conjugated Oligomers and Polymersmentioning

confidence: 99%

Section: Ecd Properties In Thin Films Of π-Conjugated Systems: Litera...mentioning

confidence: 99%

Chiroptical Properties in Thin Films of π-Conjugated Systems

2020

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“…This molecule and its derivatives are photoactive and they can suffer repeated trans− cis−trans photoisomerization cycles. 1 In addition, due to their large dipole moment, they can reorientate their axis toward a parallel alignment with the electric field of polarized light, an important property that permits to control their chiroptical behavior. Furthermore, ACAB derivatives exhibit trans−cis photoisomerization and reverse cis−trans thermal isomerization as amorphous films as well as in solution.…”

Section: Introductionmentioning

confidence: 99%

“…4-Amino-4′-cyano azobenzene (ACAB) combines both characteristics and, consequently, it has been proposed as building block for chiroptical switches. This molecule and its derivatives are photoactive and they can suffer repeated trans–cis–trans photoisomerization cycles . In addition, due to their large dipole moment, they can reorientate their axis toward a parallel alignment with the electric field of polarized light, an important property that permits to control their chiroptical behavior.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Solvent Effects on the Ground and Low-Lying Excited Free Energy Surfaces of a Push–Pull Substituted Azobenzene

et al. 2014

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The ground and low-lying excited free energy surfaces of 4-amino-4'-cyano azobenzene, a molecule that has been proposed as building block for chiroptical switches, are studied in gas phase and a variety of solvents (benzene, chloroform, acetone, and water). Solvent effects on the absorption and emission spectra and on the cis-trans thermal and photo isomerizations are analyzed using two levels of calculation: TD-DFT and CASPT2/CASSCF. The solvent effects are introduced using a polarizable continuum model and a QM/MM method, which permits one to highlight the role played by specific interactions. We found that, in gas phase and in agreement with the results found for other azobenzenes, the thermal cis-trans isomerization follows a rotation-assisted inversion mechanism where the inversion angle must reach values close to 180° but where the rotation angle can take almost any value. On the contrary, in polar solvents the mechanism is controlled by the rotation of the CN═NC angle. The change in the mechanism is mainly related to a better solvation of the nitrogen atoms of the azo group in the rotational transition state. The photoisomerization follows a rotational pathway both in gas phase and in polar and nonpolar solvents. The solvent introduces only small modifications in the nπ* free energy surface (S1), but it has a larger effect on the ππ* surface (S2) that, in polar solvents, gets closer to S1. In fact, the S2 band of the absorption spectrum is red-shifted 0.27 eV for the trans isomer and 0.17 eV for the cis. In the emission spectrum the trend is similar: only S2 is appreciably affected by the solvent, but in this case a blue shift is found.

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Photoresponsive chiral nanotubes of achiral amphiphilic azobenzene

Wang

Jia

et al. 2012

Soft Matter

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Supramolecular chirality has generally been fabricated by an aggregation process of chiral building blocks. Herein, we report the fabrication of the soft chiral nanotubes by chiral self-assembly, exclusively from a novel designed achiral carboxylic-substituted bolaamphiphilic azobenzene. Based on the studies with UV-vis absorption, circular dichroism (CD), transmission electron microscopy (TEM), and X-ray diffraction (XRD) spectra, a plausible mechanism by which a chirally helical shape emerges from the nonsymmetric packing of an achiral molecule has been proposed. Our results demonstrate a valid approach for correlating the molecular structure to the macroscopic properties, in which, by ingenious molecular design, supramolecular chirality can be achieved from achiral molecular building blocks. It was further revealed that the morphology and chirality of the self-assembled nanostructures change in response to external stimuli such as light and heat. This should open an avenue for a good understanding of the ways in which structural variation affects self-assembled structures at the molecular level. We should also find potential applications as smart carriers for the controlled release and site-specific targeting of the loading, modulated by environmental stimuli.

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Rewritable and switching chiroptical supramolecular nanolayers

Cited by 3 publications

References 81 publications

Chiroptical Properties in Thin Films of π-Conjugated Systems

Chiroptical Properties in Thin Films of π-Conjugated Systems

Theoretical Study of Solvent Effects on the Ground and Low-Lying Excited Free Energy Surfaces of a Push–Pull Substituted Azobenzene

Photoresponsive chiral nanotubes of achiral amphiphilic azobenzene

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