Functional soft materials exhibiting distinct functionalities in response to a specific stimulus are highly desirable towards the fabrication of advanced devices with superior dynamic performances. ...Herein, two novel light‐driven chiral fluorescent molecular switches have been designed and synthesized that are able to exhibit unprecedented reversible Z/E photoisomerization behavior along with tunable fluorescence intensity in both isotropic and anisotropic media. Cholesteric liquid crystals fabricated using these new fluorescent molecular switches as chiral dopants exhibit reversible reflection color tuning spanning the visible and infrared region of the spectrum. Transparent display devices have been fabricated using both low chirality and high chirality cholesteric films that operate either exclusively in fluorescent mode or in both fluorescent and reflection mode, respectively. The dual mode display device employing short pitch cholesteric film is able to function on demand under all ambient light conditions including daylight and darkness with fast response and high resolution. Moreover, the proof‐of‐concept for a “remote‐writing board” using cholesteric films containing one of the light‐driven chiral fluorescent molecular switches with ease of fabrication and operation is disclosed herein. Such optically rewritable transparent display devices enabled by light‐driven chiral fluorescent molecular switches pave a new way for developing novel display technology under different lighting conditions.
Reversible photoresponsive chiral fluorescent molecular switches for optically rewritable transparent cholesteric liquid crystal display devices are developed. Both single‐luminescent‐mode and dual‐reflective‐photoluminescent‐mode displays with desirable resolutions are demonstrated.
A journey into the nano‐world: The ability to design, use and control motor‐like functions at the molecular level sets the stage for numerous dynamic molecular systems. In his Nobel Lecture, B. L. ...Feringa describes the evolution of the field of molecular motors and explains how to program and control molecules by incorporating responsive and adaptive properties.
The ability to tune molecular self‐organization with an external stimulus is a main driving force in the bottom‐up nanofabrication of molecular devices. Light‐driven chiral molecular switches or ...motors in liquid crystals that are capable of self‐organizing into optically tunable helical superstructures undoubtedly represent a striking example, owing to their unique property of selective light reflection and which may lead to applications in the future. In this review, we focus on different classes of light‐driven chiral molecular switches or motors in liquid crystal media for the induction and manipulation of photoresponsive cholesteric liquid crystal systems and their consequent applications. Moreover, the change of helical twisting powers of chiral dopants and their capability of helix inversion in the induced cholesteric phases are highlighted and discussed in the light of their molecular geometric changes.
The ability to tune molecular self‐organization with an external stimulus is a main driving force in the bottom‐up nanofabrication of molecular devices. Light‐driven chiral molecular switches or motors in liquid crystals that are capable of self‐organizing into optically tunable helical superstructures undoubtedly represent such a striking example. In this review, we focus on different classes of light‐driven chiral molecular switches or motors in liquid crystal media for the induction and manipulation of photoresponsive cholesteric LC systems and their consequent applications.
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•Switchable systems, based on porphyrins, phthalocyanines and related macrocycles.•Various types of an input signals to trigger the tetrapyrrolic switches.•Various types of output ...signals which might be obtained from tetrapyrrolic switches.•Applications of tetrapyrrole switches in elaboration of smart materials.
Porphyrins and phthalocyanines are well-known colourful compounds, which attract much attention in various fields of science and technology, including the area of molecular switches and machines – an emerging multidisciplinary area, which is expected to provide novel classes of materials for data storage and processing, smart materials with switchable properties, etc. This review is aimed to exemplify various types of switchable systems, based on porphyrins, phthalocyanines and related macrocycles to give the link between the physical-chemical properties of the parent macrocycles, different types of input signals and mechanisms of responses, leading to detectable outputs. Specifically, attention will be paid to switching of properties which are meaningful for practical applications of porphyrinoids – change of optical characteristics, alteration of excited state dynamics, switching between different spin states and tuning of magnetic properties.
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•Transport properties of some β-diketones are studied with DFT-NEGF technique.•In these molecular switches, in most cases, the current was higher in the enol forms.•Analyzed the ...effects of electrode materials and adsorptions sites on I-V in STMHDS.
In this study, the nonequilibrium green's function (NEGF) combination with density functional theory (DFT) was used to investigate the molecular switching properties in some β-diketones with different alkyl and methoxy groups in their beta positions. The compounds used in this research are: 1,7-dimercapto-2,2,6,6-tetramethyl-3 5-heptanedione (STMHDS), 1,7-dimercapto3,5-Heptanedione (SHPDS), 1,5-dimercaptopentane-2,4-dione (SAAS), and mercaptomethyl 4-mercapto-3-oxobutanoate (SMOBS). In these four compounds, in most cases, the current in keto form is lower than in the enol form. We thoroughly examined the STMHDS molecule, including different electrodes (Pt, Au, and Ag), the types of connection states (top, bridge, and hollow), the on–off ratios, the HOMO-LUMO gaps, the I-V, and the transmission spectra. For this molecule, the best connection is hollow, so the same type of connection is considered for all calculations. With changing the enol form to keto form, the conductivity changed from the on-state (low resistance) to the off-state (high resistance). The best electrodes with the highest current ratios in STMHDS, SHPDS, SAAS, and SMOBS are Au, Au, Pt, and Ag, respectively. Because the ratios in SHPDS, SAAS, and SMOBS molecules are much smaller than that in STMHDS molecule, the transmission spectra and the HOMO-LUMO gaps cannot explain which form is more conductive.
The valence isomerization of norbornadiene (NBD) and quadricyclane (QC) has been widely studied as a potential molecular solar thermal (MOST) energy storage and release system. By combining this ...interconversion couple with C60 fullerene, a hybrid system with novel properties was created. Within this system, light‐induced switching between NBD and QC in both directions is possible, thereby transforming the former photo/thermal system into a pure photoswitch. More information can be found in the Full Paper by P. Lorenz and A. H. Hirsch on page 5220.
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Solar energy conversion and solar energy storage are key challenges for a future society with limited access to fossil fuels. Certain compounds that undergo light-induced ...isomerisation to a metastable isomer can be used for storage of solar energy, so-called molecular solar thermal systems. Exposing the compound to sun light will generate a high energy photoisomer that can be stored. When energy is needed, the photoisomer can be catalytically converted back to the parent compound, releasing the excess energy as heat. This Letter gives examples of selected molecular solar thermal systems found in the literature. The focus of the Letter is on examples where molecular design has been used to improve the performance of the molecules, and as such it may serve as an inspiration for future design. The selected examples cover five widely studied systems, notably: anthracenes, stilbenes, azobenzenes, tetracarbonyl-fulvalene-diruthenium compounds and norbornadienes.
A dual temperature‐ and light‐responsive C2H2/C2H4 separation switch in a diarylethene metal–organic framework (MOF) is presented. At 195 K and 100 kPa this MOF shows ultrahigh C2H2/C2H4 selectivity ...of 47.1, which is almost 21.4 times larger than the corresponding value of 2.2 at 293 K and 100 kPa, or 15.7 times larger than the value of 3.0 for the material under UV at 195 K and 100 kPa. The origin of this unique control in C2H2/C2H4 selectivity, as unveiled by density functional calculations, is due to a guest discriminatory gate‐opening effect from the diarylethene unit.
Photochromic diarylethene units were used to identify C2H2, leading to ultrahigh C2H2/C2H4 selectivity and promising application in C2H2/C2H4 separation at low temperature. The photochromic material can be further used as a temperature‐ and light‐responsive switch for C2H2/C2H4 separation.
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