Basicities of organometallic and other bases using the visible absorption maximum of the reference acid and its conjugate base

1970 ◽  
Vol 48 (23) ◽  
pp. 3769-3770 ◽  
Author(s):  
R. A. N. McLean ◽  
J. D. Umpleby
Keyword(s):  
Absorption Maximum ◽  
Quantitative Measure ◽  
Visible Absorption ◽  
Organic Bases ◽  
Reference Acid ◽  
Conjugate Base

The shift in the visible absorption maximum of hexanitrodiphenylamine has been used as a measure of the base strengths of some organometallic and organic bases. It is not possible to obtain a quantitative measure for stronger bases as the hexanitrodiphenylamine anion is produced. The order of base strengths for the organometallic bases studied is found to be Me3SiSMe < Me3CSMe < Me3SnSMe ≈ Me3SiNMe2.

scholarly journals Purification of commercial acriflavine by Sephadex LH-20 column chromatography.

1977 ◽  
Vol 25 (11) ◽  
pp. 1275-1277 ◽  
Author(s):  
J W Levinson ◽  
V M Maher ◽  
J J McCormick
Keyword(s):  
Aluminum Oxide ◽  
Column Chromatography ◽  
Spectral Properties ◽  
Absorption Maximum ◽  
Band Width ◽  
Visible Absorption ◽  
Theoretical Maximum

Acriflavine supplies commercially was purified by removing contaminating proflavine by chromatography on a column of Sephadex LH-20 eluded with 65% methanol. The purified acriflavine, recovered in a yield that was 52% of the theoretical maximum, had a visible absorption maximum of 452 nm with a band width of 47 nm. These spectral properties agreed with those of acriflavine purified by precipitation, repeated recrystallization and chromatography on aluminum oxide, which results in a yield of 13% at best.

scholarly journals Atomistic Insight into the Role of Threonine 127 in the Functional Mechanism of Channelrhodopsin-2

2019 ◽  
Vol 9 (22) ◽  
pp. 4905 ◽  
Author(s):  
David Ehrenberg ◽  
Nils Krause ◽  
Mattia Saita ◽  
Christian Bamann ◽  
Rajiv K. Kar ◽  
...  
Keyword(s):  
Schiff Base ◽  
Absorption Maximum ◽  
Light Adaptation ◽  
Resonance Raman Spectroscopy ◽  
Proton Pumping ◽  
Hydroxyl Group ◽  
Visible Absorption ◽  
Dark Light ◽  
Hydrogen Bonded

Channelrhodopsins (ChRs) belong to the unique class of light-gated ion channels. The structure of channelrhodopsin-2 from Chlamydomonas reinhardtii (CrChR2) has been resolved, but the mechanistic link between light-induced isomerization of the chromophore retinal and channel gating remains elusive. Replacements of residues C128 and D156 (DC gate) resulted in drastic effects in channel closure. T127 is localized close to the retinal Schiff base and links the DC gate to the Schiff base. The homologous residue in bacteriorhodopsin (T89) has been shown to be crucial for the visible absorption maximum and dark–light adaptation, suggesting an interaction with the retinylidene chromophore, but the replacement had little effect on photocycle kinetics and proton pumping activity. Here, we show that the T127A and T127S variants of CrChR2 leave the visible absorption maximum unaffected. We inferred from hybrid quantum mechanics/molecular mechanics (QM/MM) calculations and resonance Raman spectroscopy that the hydroxylic side chain of T127 is hydrogen-bonded to E123 and the latter is hydrogen-bonded to the retinal Schiff base. The C=N–H vibration of the Schiff base in the T127A variant was 1674 cm−1, the highest among all rhodopsins reported to date. We also found heterogeneity in the Schiff base ground state vibrational properties due to different rotamer conformations of E123. The photoreaction of T127A is characterized by a long-lived P2380 state during which the Schiff base is deprotonated. The conservative replacement of T127S hardly affected the photocycle kinetics. Thus, we inferred that the hydroxyl group at position 127 is part of the proton transfer pathway from D156 to the Schiff base during rise of the P3530 intermediate. This finding provides molecular reasons for the evolutionary conservation of the chemically homologous residues threonine, serine, and cysteine at this position in all channelrhodopsins known so far.

scholarly journals Solvent Effects on the UV-Visible Absorption Spectra of Some New 3-Methyl-5-(Phenylamino)-4-((4-Phenylazo-Phenyl)Azo)-2-Substituted Thiophene Dyes

2021 ◽  
Vol 11 (5) ◽  
pp. 12937-12945
Keyword(s):  
Absorption Spectra ◽  
Absorption Maximum ◽  
Bathochromic Shift ◽  
Thiophene Ring ◽  
Solvent Polarity ◽  
Visible Absorption ◽  
Chemical Structures ◽  
Effect Of Solvent ◽  
Polar Groups ◽  
Uv Visible

The preparation of 3-methyl-5-(phenylamino)-4-((4-phenylazo-phenyl)azo)thiophene dyes 4a-d, having different polar groups at the second position, was described through hetero-cyclization of the precursor 4-mercapto-4-(phenylamino)-3-((4-phenylazo-phenyl)azo)but-3-en-2-one (3) with various α-chlorinated reagents. The absorption spectra of the synthesized thiophene dyes were studied in three solvents (MeOH, CHCl3, and DMF) to correlate the effect of solvent polarity as well as chemical structures on absorption in the UV–vis region. The absorption maximum (λmax) changed from 486 to 502 nm in methanol, from 502 to 512 nm in chloroform, and from 626 to 654 nm in DMF. The benzoyl group's introduction in the second position of the thiophene ring brings the absorption maxima to higher values (bathochromic shift).

SYNTHESIS AND ELECTRO-OPTICAL PROPERTIES OF BLUE EMITTING POLY(BP-alt-BCV) CONJUGATED POLYMERS

2005 ◽  
Vol 14 (04) ◽  
pp. 535-543
Author(s):  
JEONG JU BAEK ◽  
YOUNG CHUL JEONG ◽  
LEE SOON PARK ◽  
JUNG KYUNG LEE ◽  
YOON SOO HAN ◽  
...  
Keyword(s):  
Optical Properties ◽  
Conjugated Polymers ◽  
Double Layer ◽  
Phosphonic Acid ◽  
Conjugated Polymer ◽  
Absorption Maximum ◽  
Blue Emission ◽  
Diethyl Ester ◽  
Visible Absorption ◽  
Uv Visible

A new blue electroluminescent conjugated polymer, poly(BP-alt-BCV), was prepared by Hornor–Emmons polycondensation of [5-carbazol-9-yl-3-(diethoxy-phosphorylmethyl)-2-(2-ethyl-hexyloxy)-benzyl]-phosphonic acid diethyl ester (PHBP) and 4,4′-biphenyldicarboxaldehyde (BPCA) in the presence of tert-BuOK in THF. UV-visible absorption maximum (λmax,UV, π-π* transition) of poly(BP-alt-BCV) was measured at 340 nm. PL maximum (λmax,PL) values of poly(BP-alt-BCV) were obtained at 406 and 430 nm, when excited at its own λmax,UV. It was found that double layer [ITO/poly(BP-alt-BCV)/Alq3 (50 Å)/Al] PLED exhibited maximum EL peak at 440 nm and blue emission (x = 0.1794, y = 0.1878), similar to the NTSC standard blue (x = 0.14, y = 0.08).

Octahedral cobalt(III) complexes of the chloropentammine type. XX. The preparation, properties, and reactions of some chlorocycloalkylaminebis- (ethylenediamine)cobalt(III) salts

1970 ◽  
Vol 23 (4) ◽  
pp. 707 ◽  
Author(s):  
SC Chan ◽  
TL Cheung
Keyword(s):  
Rate Constants ◽  
Ion Pair ◽  
Base Hydrolysis ◽  
Isomeric Form ◽  
Visible Absorption ◽  
First Order ◽  
Order Rate ◽  
Hydrolysis Of ◽  
Conjugate Base ◽  
Visible Absorption Spectroscopy

Salts of one isomeric form of the chlorocycloalkylaminebis(ethylenediamine)cobalt(111) series of cations have been prepared and characterized. They are tentatively assigned a cis configuration on the basis of visible absorption spectroscopy. The first-order rate constants for the solvolytic aquation of these cations have been determined at 50.5�, and the results suggest the presence of steric acceleration. The second-order rate constants for the base hydrolysis of these cations have also been determined at 0� and ionic strength of 0.1M. These results are discussed in terms of the conjugate-base/ion-pair mechanistic spectrum postulated previously.

Synthesis, Characterization and Properties of Amphiphilic Copolyfluorenes

2006 ◽  
Vol 11-12 ◽  
pp. 371-374
Author(s):  
Ai Ying Li ◽  
Jie Yun Chang ◽  
Kai Quan Wang ◽  
Lu De Lu
Keyword(s):  
Molecular Weight ◽  
Absorption Maximum ◽  
Amphiphilic Copolymers ◽  
Narrow Molecular Weight Distribution ◽  
Thermal Stabilities ◽  
Visible Absorption ◽  
1H And 13C Nmr ◽  
Good Solubility ◽  
Suzuki Polycondensation ◽  
Uv Visible

One novel fluorene-based amphiphilic copolymers has been synthesized by Suzuki polycondensation (SPC) with monomer 2,7-dibromo-9,9-bis-(3,6-dioxahepyl)fluorene and 9,9-dioctylfluorene-2,7-bis-(trimethyleneboronate). The copolyfluorenes’ molecular structure is characterized by 1H and 13C NMR as well as elemental analysis. The copolyfluorenes have high molecular weight and narrow molecular weight distribution, at the same time, are found to have good solubility and thermal stabilities. The copolyfluorenes exhibit a UV-visible absorption band in the range of 389-393 nm in both toluene solution and the film state. Upon photo-excitation around the absorption maximum wavelength, their PL spectra show a maximum peaks around at 415-427 nm.

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