A multifunctional tripodal fluorescent probe for the recognition of Cr3+, Al3+, Zn2+ and F− with controllable ESIPT processes
Hong ZhangTao SunQin RuanJiang‐Lin ZhaoLan MuXi ZengZongwen JinShao-Bo SuQingying LuoYiyong YanCarl Redshaw
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Stokes shift
Proton NMR
Proton NMR
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Detailing Hydrogen Bonding and Deprotonation Equilibria between Anions and Urea/Thiourea Derivatives
Spectrophotometric and 1H NMR titrations of N-methoxyethyl-N'-(4-nitrophenyl)thiourea (3) by Bu4NOAc show that in DMSO deprotonation of the receptor and formation of a hydrogen-bonded complex with anion proceed simultaneously but in MeCN deprotonation requires the participation of the second acetate anion. The formation constants of hydrogen-bonded complexes were determined from titrations in the presence of added acetic acid, which suppressed deprotonation. These constants together with independently measured stability constants of (AcO)2H- complexes were employed for a rigorous numerical analysis of titration results in the absence of added acid, which allowed us to determine the equilibrium deprotonation constants as well as pKa values for 3 in both solvents. Although 3 appeared to be a weaker acid than AcOH in both solvents, it can be deprotonated by acetate in dilute solutions when the concentration of liberated acetic acid is low enough. With disubstituted N,N-bis(methoxyethyl)-N'-(4-nitrophenyl)thiourea 4 only deprotonation equilibrium is observed. In contrast, both parent urea derivatives 1 and 2 cannot be deprotonated by acetate anions. Independent of the real type of equilibrium, whether it is a deprotonation or a hydrogen bonding, titration plots always can be satisfactorily fitted to a formal 1:1 binding isotherm. A relationship between apparent "binding constants" and real equilibrium constants of hydrogen bonding association and deprotonation processes is discussed.
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Coordination complex
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Two novel fluorescent naphthalimide dyes with acetylamino and amino groups were prepared for the first time by imidation, reduction and acetylation reactions from 4-nitro- 1,8-naphthalic anhydride as a starting material. The synthesized dyes were characterized by FTIR, differential scanning calorimetry (DSC), 1 HNMR, 13 CNMR, Uv-visible and fluorometery spectroscopic techniques. The absorption spectra of the dyes were examined in DMF and wavelength maxima and molar extinction coefficients of dyes were obtained. The fluorescence properties of dyes were evaluated in DMF and their Stokes shift were determined. Keywords—Synthesis, Fluorescent naphthalimide dye, Characterization, Stock's shift.
Stokes shift
Proton NMR
Molar absorptivity
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The removal of 75% of the lipid from bacteriorhodopsin caused the following: (i) decreased efficiency and rate of deprotonation of the protonated Schiff base (as monitored by absorption of the M412 intermediate); (ii) increased efficiency of deprotonation of deionized samples; (iii) a decrease by 1 unit in the pH at which deprotonation ceases; (iv) increased intensity of Eu3+ emission in Eu3+-regenerated deionized delipidated samples; (v) increased exposure of the Eu3+ sites to water; and (vi) elimination of the dependence of the deprotonation efficiency on the metal cation concentration. These results are discussed in terms of changes in the protein conformation upon delipidation, which in turn control the deprotonation mechanism.
Halobacteriaceae
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The molecular structures of 4-aminomethyl-phenylamino-bis-(3,4-dichloro-5-phenylcarbamoyl-1H-pyrrole-2-carboxamide), LH2, its deprotonated species and fluoride,chloride and hydroxide complexes were obtained by geometry optimizations using thedensity functional theory (DFT) calculations. Energetics, thermodynamic properties andequilibrium constants of deprotonation processes of the compound in the presence andabsence of fluoride, chloride and hydroxide ions were computed at the B3LYP/6-31G(d)level with zero point vibration energy (ZPVE) corrections. In gas phase, the fluoride andhydroxide ions are able to form complexes with the deprotonated species of the compoundsand finally the compounds became the free deprotonated form. However, the chloride ionsprefer to form the dichloride complexes without the deprotonation processes of thecompound. The B3LYP/6-31G(d)-optimized data of L2─ also shows a strong support for itsX-ray crystallographic structure. Keywords: anion coordination; computational chemistry; 2,5-diamidopyrrole; DFT;deprotonation.
Pyrrole
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Two iron complexes each containing a 1-ferra-2,5-diphospha-[2.1.1] ring are prepared by deprotonation reaction of cationic vinylidene complexes [Fe]CC(Ph)CH2R+ ([Fe] = (η5-C5H5)(dppe)Fe, R = CHCH2 and Ph). The deprotonation takes place at the methylene proton of the dppe ligand, which is followed by an intramolecular addition giving the product. For similar vinylidene complexes with R = CN, p-C6H4CN, and p-C6H4CF3, the deprotonation reaction gave the cyclopropenyl complexes. The deprotonation of the vinylidene complex with R = C6F5 gave both the cyclopropenyl complex and the product containing a 1-ferra-2,5-diphospha-[2.1.1] ring system. The electron-withdrawing ability of the substituent near the Cγ-methylene group of the vinylidene ligand determines the selectivity of deprotonation. Characterizations of vinylidene, cyclopropenyl complexes, and a complex containing a 1-ferra-2,5-diphospha-[2.1.1] ring are carried out using single-crystal X-ray diffraction analysis.
Methylene
Cationic polymerization
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