An ultraviolet-visible light (UV-Vis)-reversible but fluorescence-irreversible chemosensor was developed for the detection of copper. Coordination between the probe, 2-pyridylaldehyde fluorescein ...hydrazone (FHP), and Cu(2+) gave a reversible UV-Vis response, Storage of the probe-Cu complex resulted in hydrolytic cleavage of the N═C bond, which released the fluorophore (ring-opened fluorescein hydrazine) and gave irreversible fluorescence. Thus, FHP becomes a multifunctional chemosensor, and its reversibility can be controlled by the reaction time. Cu(2+) in living cells could be detected using FHP and general fluorescence methods.
An environmentally benign protocol of chemoselective transfer hydrogenation of C=C and C=O bonds with alkanols under base‐free conditions is developed by this study, wherein the cobalt‐ bidentate ...phosphine catalyst precursor is commercially available and the active low‐valent Co species could be generated in‐situ. For the conjugation enones, the vinyl group is selectively reduced, whereas with nonconjugated alkenones, the selectivity is changed to the carbonyl group. Besides, ortho‐alkenyl‐benzaldehydes/imines are well tolerated, and the reduction solely occurs at the C=O/C=N site with this protocol.
Low‐cost and sustainable: An environmentally benign protocol of Co‐bidentate phosphine complex‐catalyzed chemoselective transfer hydrogenation of C=C and C=O bonds with equivalent alkanols under base‐free conditions was developed.
The interaction between biliverdin and bovine serum albumin (BSA) has been studied by steady fluorescence spectroscopy, synchronous fluorescence and resonance light scanning spectra. The binding of ...biliverdin to BSA quenches the tryptophan residue fluorescence and the results show that both static and dynamic quenching occur together with complex formation. The binding constant and binding sites of biliverdin to BSA at pH 7.1 are calculated to be 3.33
×
10
8
L/mol and 1.54, respectively, according to the double logarithm regression curve. In addition, the distance between the biliverdin and BSA is estimated to be 1.25
nm using Föster's equation on the basis of the fluorescence energy transfer. Furthermore the synchronous fluorescence spectra show that the microenvironment of the tryptophan residues has not obvious changes, which obeys the phase distribution model. Finally, the thermodynamic data show that biliverdin molecules enter the hydrophobic cavity of BSA via hydrophobic interaction.
Without use of any surfactant or oxidant, a series of Co3O4 catalysts have been prepared from cobalt nitrate aqueous solution via a very simple liquid-precipitation method with ammonium acid ...carbonate followed by calcination at various temperatures. The catalytic performance of the Co3O4 for CO oxidation has been studied with a continuous flowing laboratory microreactor system. The results show that the CO conversion of all the samples can reach 100% at ambient temperature. The catalyst calcined at 300 °C is able to maintain its activity for CO complete oxidation more than 500 min at 25 °C and about 240 min even at −78 °C. High reaction temperature results in a high catalytic stability, while the catalytic stability decreases with further increasing the reaction temperature. Characterizations with X-ray powder diffraction and transmission electron microscopy suggest that all the samples exist as a pure Co3O4 phase with the spinel structure, the samples are apt to aggregate and the specific surface area gradually decreases with increasing the calcination temperature, which directly leads to the decrease of catalytic stability. Furthermore, the amount of active oxygen species measured by CO titration experiments appears to be critical for catalytic performance.
In this paper, the Co
3
O
4
catalysts prepared by the liquid phase precipitation method were investigated with respect to their activity and stability in CO oxidation reaction. The Co
3
O
4
catalysts ...were comparatively investigated by thermal gravimetry analysis (TG-DTG), X-ray powder diffraction (XRD), N
2
adsorption, CO titration and O
2
-temperature program desorption (O
2
-TPD). The results of XRD show that all the catalysts exist as a pure Co
3
O
4
phase with the spinel structure. The high catalytic activity observed at ambient temperature is followed by a gradual decrease. The CO titration experiments show that the Co
3
O
4
catalysts possess active oxygen species. The total amount of active oxygen species and the specific surface area decrease with increasing calcination temperature. The O
2
-TPD results indicate that O
2
−
and O
−
are the possible active oxygen species.
A protocol for a CoII/N,N′,N′′‐trihydroxyisocyanuric acid (THICA)‐catalyzed aerobic oxidative esterification and amidation of aldehydes has been developed. Preliminary insight into the mechanism ...indicates that such an oxidative C−O/N cross‐coupling reaction proceeds by masking the aldehyde in a nucleophilic addition reaction with an alkoxy/amino source, thereby keeping the highly reactive formyl group from undesired oxidation. This protocol for the oxidative esterification and amidation of aldehydes proceeds through two different pathways that are characterized by the intrinsic nucleophilicity of the alkanol and amine substrates The former occurs in the presence of p‐CH3C6H4SO3H as a cocatalyst and orthoformates as the alkoxy sources, instead of alkanols, to efficiently afford the transient acetals. In contrast, the coupling of the more nucleophilic amines with aldehydes renders a readily accessible cross‐coupling reaction that occurs without any cocatalyst but is limited by the potential inhibition of THICA upon nucleophilic substitution by an amine. Consequently, only sterically hindered amines were tolerated in this catalytic system, whereas further condensation occurred in the presence of primary amines to lead to imines.
Through THICA and thin: A protocol for a CoII/N,N′,N′′‐trihydroxyisocyanuric acid (THICA) mediated aerobic oxidative esterification and amidation of aldehydes has been developed. A variety of esters and amides were obtained in moderate to excellent yields by using this one‐step approach.
Four iron complexes {PhN(CH2)2NH(SiMe3)4FeLi·Et2O (1), PhN(CH2)3NSiMe32FeLi(Et2O) (2), PhN(CH2)2NCH(Ph)NSiMe32FeLi(Et2O)2 (3), and PhN(CH2)3NCH(Ph)NSiMe32FeLi(Et2O)2 (4)} with polydentate nitrogen ...ligands were synthesized and structurally characterized by X‐ray crystallography. The X‐ray structures of complexes 1–4 show that they crystallize in three different systems. The magnetic properties of 1–4 were investigated. The magnetization trends of magnetic field intensity show the curves of Type‐S, illustrating those complexes 1–4 are superparamagnetic.
A series of mesoporous SiO
2ZrO
2 aerogels with various zirconia content (10–90 wt%) were prepared by the sol–gel method followed by supercritical drying. The characterization of aerogels is ...performed by XRD, FT-IR,
29Si liquid-state NMR, and BET-N
2 adsorption. The results showed that (i) the aerogels have type VI (BDDT) profile which is the typical of mesopores in the interval between 2<
D
p
<50 nm; (ii) the specific surface areas varied from 340 to 730 m
2/g with (
S
BET)
MAX=735.5 m
2/g for the aerogel with 10 wt% zirconia and the surface areas decreased with the increase of zirconia; (iii) all the aerogels with different zirconia content remained amorphous or poorly crystallized after calcination in air at 500 °C; (iv) a large number of SiOZr bands existed in the aerogels indicating a homogeneous distribution of the components on the atomic scale. In addition, using inorganic salt as zirconium source instead of the expensive and toxic zirconium alkoxide is very economic.
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•Facile, fast and efficient protocols for the deuteration of calix4pyrroles.•There are no examples reporting the deuteration of calix4pyrroles.•Highlights an approach to create ...tritiated macrocyclic species with pyrrole.
Calix4pyrrole was found to be high deuterium incorporation and easy-to-make hydrogen-deuterium exchange in β-pyrrolic positions with the 98% sulphuric acid as catalyst in D2O/CH3CN–D2O/CHCl3–D2O. Compounds 2a–d were obtained by acid-catalyzed hydrogen-deuterium exchange in β-pyrrolic positions of calix4pyrroles 1a–d, respectively. Deuterium labeling at the pyrrole-β-position for compounds 1b and 1c can be achieved with nearly 100% incorporation in D2O–H2SO4 and CH3CN–D2O–H2SO4 systems, and deuterium labelling at the pyrrole-β-position for 1a and 1d is more than 90% in CHCl3–D2O–H2SO4.
The promotional effects of ZrO2 on Ni/ZrO2–SiO2 catalysts were investigated by the comparison of Ni/SiO2 and Ni/ZrO2–SiO2 activity in the hydrogenation of maleic anhydride (MA) to γ-butyrolactone ...(GBL), and by the measurements of X-ray diffraction (XRD), Fourier transform infrared (FT-IR), temperature-programmed reduction (TPR) and ammonia temperature-programmed desorption (NH3-TPD). The presence of ZrO2 led to an obvious increase of GBL yield. The promotion effect could be attributed to the possible presence of Zr4+ species on the catalyst surface owing to the higher ionicity of the Zr–O bonds, and to the proper interaction of Ni with the ZrO2-SiO2 support that is regulated by the presence of ZrO2.
