Why Do Simple Molecules with “Isolated” Phenyl Rings Emit Visible Light?

2017 ◽  
Vol 139 (45) ◽  
pp. 16264-16272 ◽  
Author(s):  
Haoke Zhang ◽  
Xiaoyan Zheng ◽  
Ni Xie ◽  
Zikai He ◽  
Junkai Liu ◽  
...  
Keyword(s):  
Visible Light ◽  
Phenyl Rings ◽  
Simple Molecules

scholarly journals Azobispyrazole Family as Photoswitches Combining (Near-)Quantitative Bidirectional Isomerization and Widely Tunable Thermal Half-Lives from Hours to Years

2021 ◽  
Author(s):  
Yixin He ◽  
Zhichun Shangguan ◽  
Zhao-Yang Zhang ◽  
Mingchen Xie ◽  
Chunyang Yu ◽  
...  
Keyword(s):  
Visible Light ◽  
Electronic Structures ◽  
Rational Design ◽  
Molecular Diversity ◽  
Molecular Design ◽  
Theoretical Investigations ◽  
Phenyl Rings

Azobenzenes <a>are one of the most attractive class of </a>molecular photoswitches. In recent endeavors of molecular design, replacing one or both phenyl rings by heteroaromatic ones is emerging as a strategy to expand the molecular diversity and to access improved photoswitch properties. However, the currently available heteroaryl azo switches generally show limitations on <i>E </i>⇆ <i>Z</i> photoisomerization yields and/or <i>Z</i>-isomer stability. Here we report a family of azobispyrazoles as new photoswitches, which combine (near-)quantitative bidirectional photoconversions and widely tunable <i>Z</i>-isomer thermal half-lives (<i>t</i><sub>1/2</sub>) from hours to years. A visible-light-activated photoswitch is also obtained. Systematic experimental and theoretical investigations reveal the different geometric and electronic structures of azobispyrazoles from those of phenylazopyrazoles, overcoming the conflict existing in the latter between effective photoconversion and <i>Z</i>-isomer stability. Our work shows the great potential of azobispyrazoles in developing photoresponsive systems and can inspire the rational design of new photoswitches making use of bis-heteroaryl azo architecture.

scholarly journals Azobispyrazole Family as Photoswitches Combining (Near-)Quantitative Bidirectional Isomerization and Widely Tunable Thermal Half-Lives from Hours to Years

2021 ◽  
Author(s):  
Yixin He ◽  
Zhichun Shangguan ◽  
Zhao-Yang Zhang ◽  
Mingchen Xie ◽  
Chunyang Yu ◽  
...  
Keyword(s):  
Visible Light ◽  
Electronic Structures ◽  
Rational Design ◽  
Molecular Diversity ◽  
Molecular Design ◽  
Theoretical Investigations ◽  
Phenyl Rings

Azobenzenes <a>are one of the most attractive class of </a>molecular photoswitches. In recent endeavors of molecular design, replacing one or both phenyl rings by heteroaromatic ones is emerging as a strategy to expand the molecular diversity and to access improved photoswitch properties. However, the currently available heteroaryl azo switches generally show limitations on <i>E </i>⇆ <i>Z</i> photoisomerization yields and/or <i>Z</i>-isomer stability. Here we report a family of azobispyrazoles as new photoswitches, which combine (near-)quantitative bidirectional photoconversions and widely tunable <i>Z</i>-isomer thermal half-lives (<i>t</i><sub>1/2</sub>) from hours to years. A visible-light-activated photoswitch is also obtained. Systematic experimental and theoretical investigations reveal the different geometric and electronic structures of azobispyrazoles from those of phenylazopyrazoles, overcoming the conflict existing in the latter between effective photoconversion and <i>Z</i>-isomer stability. Our work shows the great potential of azobispyrazoles in developing photoresponsive systems and can inspire the rational design of new photoswitches making use of bis-heteroaryl azo architecture.

Multiple Phenyl Rings appended Re-based Complexes for Strong Visible Light Absorption and DNA Binding

2021 ◽  
Author(s):  
Deepak Gupta ◽  
Bholey Singh ◽  
Balaram Pani
Keyword(s):  
Dna Binding ◽  
Visible Light ◽  
Structural Feature ◽  
Light Absorption ◽  
Triphenylphosphine Oxide ◽  
Chelating Ligands ◽  
Visible Light Absorption ◽  
Phenyl Rings ◽  
Acyclic Complexes

A series of facialRe(CO)3based acyclic complexes (13) possessing N∩O bis-chelating ligands and triphenylphosphine-oxide donor were synthesized and characterized. The most interesting structural feature of these complexes is that both the...

scholarly journals Azobispyrazole Family as Photoswitches Combining (Near-)Quantitative Bidirectional Isomerization and Widely Tunable Thermal Half-Lives from Hours to Years

2021 ◽  
Author(s):  
Yixin He ◽  
Zhichun Shangguan ◽  
Zhao-Yang Zhang ◽  
Mingchen Xie ◽  
Chunyang Yu ◽  
...  
Keyword(s):  
Visible Light ◽  
Electronic Structures ◽  
Rational Design ◽  
Molecular Diversity ◽  
Molecular Design ◽  
Widespread Application ◽  
Theoretical Investigations ◽  
Phenyl Rings

Azobenzenes <a>are classical </a>molecular photoswitches that have received widespread application. In recent endeavors of molecular design, replacing one or both phenyl rings by heteroaromatic ones is emerging as a strategy to expand the molecular diversity and to access improved photoswitch properties. However, the currently available heteroaryl azo switches generally show limitations on <i>E </i>⇆ <i>Z</i> photoisomerization yields and/or <i>Z</i>-isomer stability. Here we report a family of azobispyrazoles as new photoswitches, which combine (near-)quantitative bidirectional photoconversions and widely tunable <i>Z</i>-isomer thermal half-lives (<i>t</i><sub>1/2</sub>) from hours to years. A visible-light-activated photoswitch is also obtained. Systematic experimental and theoretical investigations reveal the different geometric and electronic structures of azobispyrazoles from those of phenylazopyrazoles, overcoming the conflict existing in the latter between effective photoconversion and <i>Z</i>-isomer stability. Our work shows the great potential of azobispyrazoles in developing photoresponsive systems and can inspire the rational design of new photoswitches making use of bis-heteroaryl azo architecture.

Photochemical Evolution of Interstellar/Precometary Organic Material

1997 ◽  
Vol 161 ◽  
pp. 23-47 ◽  
Author(s):  
Louis J. Allamandola ◽  
Max P. Bernstein ◽  
Scott A. Sandford
Keyword(s):  
Origin Of Life ◽  
Building Blocks ◽  
Complex Species ◽  
Infrared Observations ◽  
Interstellar Ice ◽  
Polycyclic Aromatic ◽  
Ultraviolet Photolysis ◽  
The Origin Of Life ◽  
Simple Molecules ◽  
Complex Organic

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.

Studies of metaphase chromosomes in the scanning transmission x-ray microscope: Image fidelity, radiation damage and specimen preparation

1992 ◽  
Vol 50 (2) ◽  
pp. 1038-1039
Author(s):  
Shawn Williams ◽  
Xiaodong Zhang ◽  
Susan Lamm ◽  
Jack Van’t Hof
Keyword(s):  
Visible Light ◽  
Radiation Damage ◽  
Cross Section ◽  
Imaging Techniques ◽  
Dose Range ◽  
Specimen Preparation ◽  
X Rays ◽  
Metaphase Chromosomes ◽  
X Ray ◽  
Scanning Transmission

The Scanning Transmission X-ray Microscope (STXM) is well suited for investigating metaphase chromosome structure. The absorption cross-section of soft x-rays having energies between the carbon and oxygen K edges (284 - 531 eV) is 6 - 9.5 times greater for organic specimens than for water, which permits one to examine unstained, wet biological specimens with resolution superior to that attainable using visible light. The attenuation length of the x-rays is suitable for imaging micron thick specimens without sectioning. This large difference in cross-section yields good specimen contrast, so that fewer soft x-rays than electrons are required to image wet biological specimens at a given resolution. But most imaging techniques delivering better resolution than visible light produce radiation damage. Soft x-rays are known to be very effective in damaging biological specimens. The STXM is constructed to minimize specimen dose, but it is important to measure the actual damage induced as a function of dose in order to determine the dose range within which radiation damage does not compromise image quality.

Scanning luminescence x-ray microscopy: Progress toward selective staining using microspheres

1994 ◽  
Vol 52 ◽  
pp. 74-75
Author(s):  
C. Jacobsen ◽  
J. Fu ◽  
S. Mayer ◽  
Y. Wang ◽  
S. Williams
Keyword(s):  
Visible Light ◽  
Active Sites ◽  
Light Emission ◽  
Chinese Hamster ◽  
Polystyrene Spheres ◽  
Good Resistance ◽  
X Ray ◽  
Selective Staining ◽  
Visible Light Emission ◽  
Specific Labelling

In scanning luminescence x-ray microscopy (SLXM), a high resolution x-ray probe is used to excite visible light emission (see Figs. 1 and 2). The technique has been developed with a goal of localizing dye-tagged biochemically active sites and structures at 50 nm resolution in thick, hydrated biological specimens. Following our initial efforts, Moronne et al. have begun to develop probes based on biotinylated terbium; we report here our progress towards using microspheres for tagging.Our initial experiments with microspheres were based on commercially-available carboxyl latex spheres which emitted ~ 5 visible light photons per x-ray absorbed, and which showed good resistance to bleaching under x-ray irradiation. Other work (such as that by Guo et al.) has shown that such spheres can be used for a variety of specific labelling applications. Our first efforts have been aimed at labelling ƒ actin in Chinese hamster ovarian (CHO) cells. By using a detergent/fixative protocol to load spheres into cells with permeabilized membranes and preserved morphology, we have succeeded in using commercial dye-loaded, spreptavidin-coated 0.03μm polystyrene spheres linked to biotin phalloidon to label f actin (see Fig. 3).

Photocatalyst-free decarboxylative aminoalkylation of imidazo[1,2-a]pyridines with N-aryl glycines enabled by visible light

2019 ◽  
Vol 6 (21) ◽  
pp. 3693-3697 ◽  
Author(s):  
Jiu-Jian Ji ◽  
Zhi-Qiang Zhu ◽  
Li-Jin Xiao ◽  
Dong Guo ◽  
Xiao Zhu ◽  
...  
Keyword(s):  
Visible Light

A novel, green and efficient visible-light-promoted decarboxylative aminoalkylation reaction of imidazo[1,2-a]pyridines with N-aryl glycines has been described.

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