scholarly journals Fused bis-azacalixphyrin that reaches NIR-II absorptions

2020 ◽  
Vol 56 (6) ◽  
pp. 896-899 ◽  
Author(s):  
Lucien Lavaud ◽  
Cloé Azarias ◽  
Gabriel Canard ◽  
Simon Pascal ◽  
Joachim Galiana ◽  
...  
Keyword(s):  
Absorption Band ◽  
New Class ◽  
Intense Absorption Band ◽  
Intense Absorption

The fusion of two azacalixphyrins produces a new class of NIR-II dyes showing an intense absorption band in the 1000–1200 nm NIR range.

BF2 complexes of 1,3-diketones on the surface of phosphorus dendrimers: synthesis and study of the photoluminescence properties

2017 ◽  
Vol 95 (9) ◽  
pp. 948-953 ◽  
Author(s):  
Cédric Rouxel ◽  
Olivier Mongin ◽  
Aurélien Hameau ◽  
Armelle Ouali ◽  
Mireille Blanchard-Desce ◽  
...  
Keyword(s):  
Absorption Band ◽  
Hypsochromic Shift ◽  
Photoluminescence Properties ◽  
Intense Absorption Band ◽  
Intense Absorption

Difluoroboron complexes of monomeric and dimeric diketones and of generations 0–4 of phosphorus dendrimers ended by diketone ligands are synthesized and characterized. Their photoluminescence properties are measured. All compounds exhibit an intense absorption band in the near UV region. Both model dimers and dendrimers show a marked hypsochromic shift of this absorption band compared with the monomeric difluoroboron complex. The fluorescence of the dioxaborine complex subunit in the multichromophoric dendritic architectures is quenched compared with the emission of the isolated monomeric fluorophore, presumably due to interactions between the terminal groups of dendrimers.

scholarly journals VII. On the relations of turacin and turacoporphyrin to the colouring matter of the blood

1896 ◽  
Vol 59 (353-358) ◽  
pp. 339-342 ◽  
Keyword(s):  
Absorption Band ◽  
Royal Society ◽  
Intense Absorption Band ◽  
Intense Absorption ◽  
Derivatives Of

In a recent paper read before the Royal Society, I have shown that the intense absorption band in the extreme violet, which is observed, by means of photography, in the spectrum of highly diluted solutions of hemoglobin and its compounds, is (with slight changes in its position) exhibited by certain of the derivatives of the blood colouring matter, e. g ., by hemochromogen and the compounds of hematin, and by that remarkably interesting coloured but iron-free derivative of the latter body, hematoporphyrin.

scholarly journals FAR-INFRARED STUDIES OF THE STATE OF IONICAGGREGATION IN MIXTURES OF POLYETHERURETHANE AND K IONOMER STYRENE COPOLYMER WITH ACRYLIC ACID

2020 ◽  
pp. 150-160
Author(s):  
Валерий Александрович Рыжов
Keyword(s):  
Spectral Analysis ◽  
Absorption Band ◽  
Ion Pairs ◽  
Far Infrared ◽  
Carboxyl Groups ◽  
Styrene Copolymer ◽  
Ionic Groups ◽  
Intense Absorption Band ◽  
Infrared Studies ◽  
Intense Absorption

Методом спектрального анализа в дальнем (70 - 420 см) ИК-диапазоне исследовано влияние введения ионных групп на формирование сетки физических связей в композитах на основе полиэфир уретана и сополимера стирола. Анализ спектров ПУИ / Ст-со-АК (К+) композитов показал, что при увеличении содержания Ст-со-АК (К+) в системе образуется новая сетка межмолекулярных (ион-молекулярных) связей. Появление интенсивной полосы поглощения при ~ 180 см, обусловленной колебаниями катионов К+ в электростатической области анионов (СОО-) карбоксильных групп, её значительная полуширина и наличие максимумов при 145, 155, 177, 185, и 200 см свидетельствуют об образовании различных по организации форм катион-анионных ассоциатов в системе: от простых ионных пар до сложных мультиплетов и кластеров. He effect of the introduction of ionic groups on the formation of a network of physical bonds in composites based on polyether urethane (PEUI) and styrene copolymer (S-co-AA (K+)) was studied by the method of spectral analysis in the far (70-420 cm) IR range. An analysis of the spectra of PEUI / S-co-AA (K+) composites showed that with an increase in the content of S-co-AA (K+), a new network of intermolecular (ion-molecular) bonds forms in the system. The appearance of an intense absorption band at ~ 180 cm, due to vibrations of K+ cations in the electrostatic region of anions (COO-) carboxyl groups, its significant half width and the presence of maxima at 145, 155, 177, 185, and 200 cm indicate the formation of various on the organization of forms of cation-anion associates in the system: from simple ion pairs to complex multiplets and clusters.

scholarly journals The chemistry of vitamin B12. The coordination of biologically important molecules

1970 ◽  
Vol 120 (2) ◽  
pp. 263-269 ◽  
Author(s):  
H. A. O. Hill ◽  
J. M. Pratt ◽  
R. G. Thorp ◽  
B. Ward ◽  
R. J. P. Williams
Keyword(s):  
Charge Transfer ◽  
Absorption Band ◽  
Hydrogen Bonds ◽  
Vitamin B12 ◽  
Extinction Coefficient ◽  
Equilibrium Constants ◽  
Thiol Group ◽  
Intense Absorption Band ◽  
Intense Absorption ◽  
A Charge

The following equilibrium constants (given as logK in units of m−1) were determined for the substitution of co-ordinated H2O in aquocobalamin by glycine (bound through N) 5.8, cysteine (bound through S) 6.0 or 8.3, depending on the value chosen for the pK of the thiol group, and phenolate 2.9. The spectrum of the phenolate cobalamin shows an additional intense absorption band at 468nm with a molar extinction coefficient of 1.1×104, which is assigned to a charge transfer from the phenolate to the cobalt ion. Equilibrium constants have also been determined for the equilibria between adenylcobamide cyanide and CN−, HO− and H+, which show that the adenine is more easily displaced by CN− and HO− than is 5,6-dimethylbenziminazole in vitamin B12, but can be protonated by acid while still remaining co-ordinated to the cobalt. It is shown that in the binding of corrinoids to proteins and polypeptides the formation of hydrogen bonds is far more important than co-ordination by the metal.

Ultraviolet spectrum of domoic acid

1989 ◽  
Vol 67 (9) ◽  
pp. 1421-1425 ◽  
Author(s):  
Michael Falk ◽  
John A. Walter ◽  
Paul W. Wiseman
Keyword(s):  
Absorption Band ◽  
Domoic Acid ◽  
Ultraviolet Spectrum ◽  
Acid Solutions ◽  
Intense Absorption Band ◽  
Intense Absorption

The ultraviolet spectrum of aqueous domoic acid solutions has an intense absorption band, whose λmax shifts from 240.0 ± 0.3 nm at pH 1.3 to 244.7 ± 0.3 nm at pH 12.3. At the same time, its εmax increases from 24250 to 26700 L mol−1 cm−1. At pH 7 λmax is 242.8 ± 0.3 nm and εmax is 26035 ± 200 L mol−1 cm−1 Analysis of the variation of λmax and εmax with pH allowed us to estimate the values of these quantities for each of the five stages of protonation of domoic acid and to verify the pK values reported by Takemoto and Daigo. Keywords: ultraviolet spectrum, pK values, protonation, domoic acid.

scholarly journals Propeller-Shaped Aluminum Complexes with an Azaperylene Core in the Ligands

Inorganics ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 109
Author(s):  
Masahiro Tsukao ◽  
Yoshifumi Hashikawa ◽  
Nana Toyama ◽  
Masahiro Muraoka ◽  
Michihisa Murata ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Blue Color ◽  
Potential Utility ◽  
X Ray Diffraction ◽  
X Ray ◽  
Packing Structure ◽  
Deep Blue ◽  
Intense Absorption Band ◽  
Palladium Catalyzed ◽  
Intense Absorption

Tris(8-hydroxyquinoline) aluminum(III) (Alq3) and its derivatives, characterized by a propeller-shaped three-dimensionally π-conjugated structure, have been intensively studied in the few past decades on account of their potential utility in optoelectronic applications. Reported herein are the synthesis and properties of π-extended Alq3 complexes that contain an azaperylene core in each ligand. Intramolecular palladium-catalyzed direct C–H arylations or base-promoted arylations were employed to prepare these large Alq3 analogues. A single-crystal X-ray diffraction analysis of one of the obtained Al complexes revealed a unique three-dimensional packing structure within the crystal, i.e., a honeycomb packing along the ab-plane and columnar π-stacks along the c-axis. An Alq3 analogue with azaperylene-dicarboximide ligands exhibited deep blue color in solution with an intense absorption band that extended to 780 nm (λmax = 634 nm; ε = 58,000 M−1 cm−1).

In Situ microscopy of the anodic etching of silicon

1995 ◽  
Vol 53 ◽  
pp. 232-233
Author(s):  
Frances M. Ross ◽  
Peter C. Searson
Keyword(s):  
Composite Structures ◽  
High Surface ◽  
High Surface Area ◽  
Chemical Properties ◽  
Selective Etching ◽  
Silicon On Insulator ◽  
Second Phase ◽  
Porous Layers ◽  
New Class ◽  
Porous Semiconductors

Porous semiconductors represent a relatively new class of materials formed by the selective etching of a single or polycrystalline substrate. Although porous silicon has received considerable attention due to its novel optical properties1, porous layers can be formed in other semiconductors such as GaAs and GaP. These materials are characterised by very high surface area and by electrical, optical and chemical properties that may differ considerably from bulk. The properties depend on the pore morphology, which can be controlled by adjusting the processing conditions and the dopant concentration. A number of novel structures can be fabricated using selective etching. For example, self-supporting membranes can be made by growing pores through a wafer, films with modulated pore structure can be fabricated by varying the applied potential during growth, composite structures can be prepared by depositing a second phase into the pores and silicon-on-insulator structures can be formed by oxidising a buried porous layer. In all these applications the ability to grow nanostructures controllably is critical.

The microtubule associated protein (MAP) tau forms a new class of triple-stranded left-hand helical fibrous protein polymer

1992 ◽  
Vol 50 (1) ◽  
pp. 540-541
Author(s):  
G. C. Ruben ◽  
K. Iqbal ◽  
I. Grundke-Iqbal ◽  
H. Wisniewski ◽  
T. L. Ciardelli ◽  
...  
Keyword(s):  
Axial Ratio ◽  
Normal Structure ◽  
Paired Helical Filaments ◽  
Left Hand ◽  
New Class ◽  
Protein Polymer ◽  
Fibrous Protein ◽  
Protein Map ◽  
Neurotransmitter Transport ◽  
Alzheimer Neurofibrillary Tangles

In neurons, the microtubule associated protein, tau, is found in the axons. Tau stabilizes the microtubules required for neurotransmitter transport to the axonal terminal. Since tau has been found in both Alzheimer neurofibrillary tangles (NFT) and in paired helical filaments (PHF), the study of tau's normal structure had to preceed TEM studies of NFT and PHF. The structure of tau was first studied by ultracentrifugation. This work suggested that it was a rod shaped molecule with an axial ratio of 20:1. More recently, paraciystals of phosphorylated and nonphosphoiylated tau have been reported. Phosphorylated tau was 90-95 nm in length and 3-6 nm in diameter where as nonphosphorylated tau was 69-75 nm in length. A shorter length of 30 nm was reported for undamaged tau indicating that it is an extremely flexible molecule. Tau was also studied in relation to microtubules, and its length was found to be 56.1±14.1 nm.

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