Observing the water molecule in macromolecules and aqueous media using infrared spectrometry

2003 ◽  
Vol 648 (1-2) ◽  
pp. 27-47 ◽  
Author(s):  
Y. Maréchal
Keyword(s):  
Water Molecule ◽  
Aqueous Media ◽  
Infrared Spectrometry

Nitrogenous chelate complexes of transition metals. VI. Complexes of copper(II) with 2,2',2'-terpyridine

1970 ◽  
Vol 23 (4) ◽  
pp. 673 ◽  
Author(s):  
CM Harris ◽  
TN Lockyer
Keyword(s):  
Aqueous Solution ◽  
Transition Metals ◽  
Water Molecule ◽  
General Type ◽  
Aqueous Media ◽  
Chelate Complexes ◽  
Excess Copper ◽  
Complexes Of Transition Metals ◽  
Amine Ligands

A series of compounds of the general type Cu(terpy)X2 (terpy = 2,2',2"- terpyridine; X = Cl, Br, I, NCS) have been prepared. The above complexes are sparingly soluble in non-aqueous media in which they show some ionization to yield species of the kind [Cu(terpy)X]+ which are isolable as their perchlorate salts. Reaction of terpyridine with excess copper(11) perchlorate yields [Cu(terpy)-(HzO)](ClO4)2. The water molecule can be replaced by both mono- and bi-dentate amine ligands giving the complexes Cu(terpy)L](ClO4)2 (L = NH3, py, bipy). Conductimetric titrations in non-aqueous solvents show that Cu(terpy)(H2O)]2+ reacts with halide ion to give, in turn, [Cu(terpy)X]+ and Cu(terpy)X2. The bis-terpyridine complexes [Cu(terpy)2]X2,nH2O (X = ClO4, n = 1; X = NCS, n = 2; X = I, n = 1) have also been prepared. [Cu(terpy)2]2+ is stable in the presence of halide ion in aqueous solution but in non-aqueous solution rearrangement to the corresponding mono-complex Cu(terpy)X2 is instantaneous. This was confirmed by conductimetric titrations. Reaction of terpyridine with excess copper(11) chloride affords a complex Cuz(terpy)Cl4, which is shown to be Cu(terpy)Cl][CuCl3].

New Mechanistic Approach in the Enamine-Based Asymmetric Organocatalysis

2021 ◽  
Author(s):  
András A. Gurka
Keyword(s):  
Water Molecule ◽  
Transition State ◽  
Aqueous Media ◽  
Initial Step ◽  
Aldol Reactions ◽  
Asymmetric Aldol ◽  
Mechanistic Approach ◽  
Asymmetric Organocatalysis ◽  
Organocatalytic Reactions ◽  
Proline Derivatives

Abstract During the course of my research in asymmetric organocatalysis the inversion of enantioselectivity was observed in the asymmetric aldol reactions of acetone with different aldehydes catalyzed by amphiphilic proline derivatives in aqueous media varying only achiral components. It was not possible to explain the explored dual stereocontrol with the existing models, therefore I proposed a new mechanism for asymmetric aldol reactions catalyzed by l-amino acid derivatives in aqueous media and explained the explored phenomenon of inversion of enantioselectivity with different structures of micelle-stabilized transition state described as a metal-free version of the Zimmermann-Traxler model with explicit participation of a water molecule. Contrary to the existing models, according to the proposed mechanism the formation of new bonds proceeds directly in the transition state stabilized by a water molecule without the additional step of product iminium ion hydrolysis. The proposed mechanism has universal character, it is consistent with experimental results and general theoretical conceptions and it is applicable to all enamine-based asymmetric organocatalytic reactions carried out not only in aqueous, but in organic media as well, because the initial step of catalytic cycle, which involves the formation of an enamine from the carbonyl compound and proline (derivative), liberates one water molecule.

Photocatalytic degradation of persistent organic pollutants under visible irradiation by TiO2 catalysts sensitized with Zn(II) and Co(II) tetracarboxy-phthalocyanines

2016 ◽  
Vol 20 (08n11) ◽  
pp. 1190-1199 ◽  
Author(s):  
Yaghub Mahmiani ◽  
Altuğ Mert Sevim ◽  
Ahmet Gül
Keyword(s):  
Photocatalytic Degradation ◽  
Organic Pollutants ◽  
Persistent Organic Pollutants ◽  
Diffuse Reflectance Spectroscopy ◽  
Aqueous Media ◽  
Visible Region ◽  
Gas Chromatography Mass Spectrometry ◽  
Infrared Spectrometry ◽  
Visible Irradiation ◽  
The Difference

Photo-excitation under visible light has been an important step to acquire solar-driven TiO2 photocatalysts and dye sensitization has been used frequently to extend the optical response of TiO2 into the visible region. In the present work, new heterogeneous photocatalysts were prepared by anchoring carboxylic acid substituted Zn(II) and Co(II) phthalocyanines onto polycrystalline TiO2 surface and their photocatalytic activities were investigated. Due to covalent bonding of carboxy-terminated molecules onto TiO[Formula: see text]semiconductors, we synthesized symmetric 4-hydroxybenzoic acid-bearing metallophthalocyanines as dye sensitizer molecules. Heterogeneous composites having titanium dioxide and metallophthalocyanines anchored via CO–O–TiO2 bonds were characterized by using X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FT-IR), and ultraviolet-visible diffuse reflectance spectroscopy. The optimum loading value of the dyes on TiO2 were 0.98 [Formula: see text]mol/g TiO2 for CoPc and 0.86 [Formula: see text]mol/g TiO2 for ZnPc, nearly independent of the amount of TiO2 used. These newly obtained heterogeneous photocatalysts were employed in the photocatalytic degradation of 4-chlorophenol(4-CP), chlorobenzene(CB) and 1,2,4-trichlorobenzen(TCB) in aqueous media under visible irradiation. Gas chromatography-mass spectrometry (GC-MS) was used for quantitation. The new photocatalysts showed excellent activities with visible-region irradiation in the photocatalytic degradation of persistent organic pollutants (POPs) as compared to the control experiments used with untreated TiO2 and the difference was attributed to the cooperation of the two elements, namely TiO2 and MPc. Experiments show that in two hours nearly complete degradation of POPs were observed.

Comparison between Methods of Biological Crust Removal on Granite

2013 ◽  
Vol 548 ◽  
pp. 317-325 ◽  
Author(s):  
Santiago Pozo ◽  
Cristina Montojo ◽  
Teresa Rivas ◽  
Ana Jesús López-Díaz ◽  
Maria Paula Fiorucci ◽  
...  
Keyword(s):  
Benzalkonium Chloride ◽  
Aqueous Media ◽  
Infrared Spectrometry ◽  
Nw Spain ◽  
Cleaning Method ◽  
Additional Information ◽  
Biological Crust ◽  
Cleaning Procedures ◽  
Ftir Technique ◽  
Cleaning Methods

This paper presents the evaluation of the efficacy of the removal of biological crust from ornamental granites. The removal was made applying different procedures and the efficiency was evaluated by means of optic and scanning electron microscopy (SEM), Fourier Transformed Infrared spectrometry (FTIR) and colour measures (CIE-L*a*b* colour spaces). Among the cleaning procedures, an abrasive cleaning method, several chemicals-based methods applied by brush in aqueous media (using acids, bleach, benzalkonium chloride, ethanol and others) and laser (Nd:YVO4 at 355 nm) were used. This last method was previously found very efficient in removing graffiti and biological crusts in other granites. The present study was conducted on a granite of great commercial value from Galicia (NW Spain) and traditionally used on construction of historical buildings in this region and abroad. Slabs of this granite with an intense biological crust were used. Before the cleaning procedures, the biological crust was characterized by the same techniques to establish the comparison between Pre and Post cleaning. The efficacy in the crust removal was evaluated with optic and electronic microscopy; the best cleaning methods were the acid-based methods and laser. In both cases, no biological remains were found on the cleaning surfaces. Hydrogommage (the abrasive cleaning method) obtained intermediate results, and benzalkonium chloride cleaning showed the worst effectiveness. FTIR technique helped to identify the presence of organic signals of biological crust; and also, it provided useful information on the contaminant remains on the stone after cleaning and on mineral damages. Colour differences after cleaning gave additional information about the efficiency of the cleaning.

Highly efficient and selective photocatalytic CO2 to CO conversion in aqueous solution

2020 ◽  
Vol 56 (27) ◽  
pp. 3851-3854 ◽  
Author(s):  
Xiaomin Chai ◽  
Hai-Hua Huang ◽  
Huiping Liu ◽  
Zhuofeng Ke ◽  
Wen-Wen Yong ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Photocatalytic Performance ◽  
Aqueous Media ◽  
Highly Efficient ◽  
Co Conversion

A Co-based complex displayed the highest photocatalytic performance for CO2 to CO conversion in aqueous media.

Using of modified-bentonite as low-cost sorbent for removal of methylene blue dye from aqueous solution

2020 ◽  
Vol 27 (2) ◽  
pp. 45-54
Author(s):  
Saraa Muwafaq Ibrahim ◽  
Ziad T. Abd Ali
Keyword(s):  
Aqueous Solution ◽  
Methylene Blue ◽  
Silanol Group ◽  
Infrared Spectrometry ◽  
Blue Dye ◽  
Ammonium Bromide ◽  
Vibration Band ◽  
Order Kinetic ◽  
Methylene Blue Dye ◽  
Modified Bentonite

Batch experiments have been studied to remove methylene blue dye (MB) from aqueous solution using modified bentonite. The modified bentonite was synthesized by replacing exchangeable calcium cations in natural bentonite with cationic surfactant cetyl trimethyl ammonium bromide (CTAB). The characteristics of modified bentonite were studied using different analysis such as Scanning electronic microscopy (SEM), Fourier transform infrared spectrometry (FTIR) and surface area. Where SEM shows the natural bentonite has a porous structure, a rough and uneven appearance with scattered and different block structure sizes, while the modified bentonite surface morphology was smooth and supplemented by a limited number of holes. On other hand, (FTIR) analysis that proved NH group aliphatic and aromatic group of MB and silanol group are responsible for the sorption of contaminate. The organic matter peaks at 2848 and 2930 cm-1 in the spectra of modified bentonite which are sharper than those of the natural bentonite were assigned to the CH2 scissor vibration band and the symmetrical CH3 stretching absorption band, respectively, also the 2930 cm-1 peak is assigned to CH stretching band. The batch study was provided the maximum removal efficiency (99.99 % MB) with a sorption capacity of 129.87 mg/g at specified conditions (100 mg/L, 25℃, pH 11 and 250rpm). The sorption isotherm data fitted well with the Freundlich isotherm model. The kinetic studies were revealed that the sorption follows a pseudo-second-order kinetic model which indicates chemisorption between sorbent and sorbate molecules.

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