Femtosecond transient absorption, Raman, and electrochemistry studies of tetrasulfonated copper phthalocyanine in water solutions

Ultrafast time-resolved electronic spectra of the primary events induced in the copper tetrasulfonated phthalocyanine Cu(tsPc)4-) in aqueous solution has been measured by femtosecond pump-probe transient absorption spectroscopy. The primary events initiated by the absorption of a photon occurring within the femtosecond time scale are discussed on the basis of the electron transfer mechanism between the adjacent phthalocyanine rings proposed recently in our laboratory. The femtosecond transient absorption results are compared with the low temperature emission spectra obtained with Raman spectroscopy and the voltammetric curves.     

Adsorption of lanthanides on mordenite from nitrate medium

The adsorption of lanthanides (except for Pm) on mordenite was investigated under various solution conditions of nitrate ion concentrations ([NO*3]: 0.001-2 mol/dm3) and total lanthanide concentrations (0.0005 mol/dm3). Solutions of lanthanide nitrates were equilibrated with zeolite samples at 296 K. A concave tetrad effect was evident in the change of logK d values within the lanthanide series and an explanation by a comparison of covalence in Ln-O bonds existing in triple bond Al-O(1/3Ln)-Si species found in the zeolite phase and in Ln(H2O)3+x or Ln(NO3) n-3 n complexes formed in the aqueous phase is presented. The decreasing trend in C1 and C3 coefficients, which are the function of E1 and E3 Racah f-interelectron repulsion parameters, is evidence of the magnification of covalence in Ln-O bond in the series triple bond S-iO(1/3Ln)-Al triple bond 相似文献   

Effects of reagents’ nature on mechanochemical synthesis of calcium titanate

The effect of alkaline hydrothermal activation of class-C fly ash belite cement was studied using thermal analysis (TG/DTG) by determining the increase in the combined water during a period of hydration of 180 days. The results were compared with those obtained for a belite cement hydrothermally activated in water. The two belite cements were fabricated via the hydrothermal-calcination route of class-C fly ash in 1 M NaOH solution (FABC-2-N) or demineralised water (FABC-2-W). From the results, the effect of the alkaline hydrothermal activation of belite cement (FABC-2-N) was clearly differentiated, mainly at early ages of hydration, for which the increase in the combined water was markedly higher than that of the belite cement that was hydrothermally activated in water. Important direct quantitative correlations were obtained among physicochemical parameters, such as the combined water, the BET surface area, the volume of nano-pores, and macro structural engineering properties such as the compressive mechanical strength.     

Co-digestion of agricultural and industrial wastes

The efficiency of anaerobic digestion process is dependent on the type and composition of the material to be digested. This work examines the co-digestion of corn silage, beet pulp silage, carrot residues, and cheese whey in different configurations together with a glycerin fraction — the waste product of transestrification of oils (biodiesel production) in a 25 L bioreactor operated mesophically in a quasi-continuous mode. Co-digestion of corn silage with carrot residues appeared to be more effective than that with cheese whey resulting in the gas production rate equal to 5.9 L L⁻¹ d⁻¹ and 1.4 L L⁻¹ d⁻¹, respectively. The performed experiments showed that a combination of three substrates: corn silage, cheese whey, and glycerin fraction resulted in the highest methane content equal to 61 % and the biogas production rate of 1.8 L L⁻¹ d⁻¹.     

DFT studies on tautomeric preferences of 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione in the gas phase and in solution

Density functional theory (DFT) calculations show that in vacuum such α-diketone as 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione is much less stable than its enolimine–enaminone ((1Z,3Z)-3-hydroxy-4-(pyridin-2-yl)-1-(quinolin-2(1H)-ylidene)but-3-en-2-one) and dienaminone tautomers ((1Z,3Z)-1-(pyridin-2-yl)-4-(quinolin-2-yl)buta-1,3-diene-2,3-diol). Other its tautomers (multiple basic and acidic centers in their molecules enable multiple proton transfer to take place) are even more labile. Strength of the intramolecular hydrogen bonds and aromatic character of the (quasi)rings [proved by the Harmonic Oscillator Model of Aromaticity (HOMA) index] in their molecules were found to be responsible for the observed tautomeric preferences. Polar and basic solvent disfavors and favors the enolimine and enaminone tautomers, respectively.     

Identification of acrylate copolymers using pyrolysis and gas chromatography

A combination of pyrolysis and gas chromatography were used to investigate thermal degradation products formed from acrylic copolymers containing alkyl acrylate and methacrylate. The method provided an analytical tool for characterizing the chemical composition and structure of the degradation products. Thermal degradation of the synthesized copolymers was analyzed using isothermal (250 °C) pyrolysis–gas chromatography. The degradation process, and the nature and amount of pyrolysis products, provides relevant information about the thermal degradation of acrylic copolymers and the mechanism of pyrolysis. During pyrolysis, the formation of corresponding olefins, alcohols, acrylates and methacrylate was observed.     

Fluorescent chemosensors for metal ions based on 3-(2-benzoxazol-5-yl)alanine skeleton

The ability of new chelate ligands, benzoxazol-5-yl-alanine derivatives substituted in position 2 by heteroaromatic substituent, to form complexes with selected metal ions in acetonitrile are studied by means of absorption and steady-state and time-resolved fluorescence spectroscopy. Among the ligands studied, only azaaromatic derivatives form stable complexes with transition metal ions in the ground state. Their absorption bands are bathochromically shifted enabling to use those ligands as ratiometric sensors. The fluorescence of each ligand is quenched by metal ions, however, in the presence of Cd(II) and Zn(II) ions a new red shifted emission band is observed.      

Structural and thermal properties of rare earth complexes with 2,2′-biphenyldicarboxylic acid

Rare earth complexes with 2,2′-biphenyldicarboxylic acid (diphenic acid = H₂dpa) were obtained as hydrated precipitates of the general formula Ln₂(C₁₄H₈O₄)₃∙nH₂O, where n = 3 for the of Y(III) and Ce(III)–Er(III) and n = 6 for La(III), Tm(III), Yb(III) and Lu(III) complexes. On heating in air atmosphere complexes lose all water molecules in the temperature range 30–210 °C in one step and form anhydrous compounds, which are stable up to 315–370 °C. During further heating they decompose to oxides. The trihydrated compounds are crystalline powders whereas the hexahydrated are amorphous solids. The trihydrated complexes crystallize in the monoclinic (Pr(III) and Ce(III) complexes) and triclinic (Y(III) and Nd(III)–Er(III) complexes) crystal systems.     

Spectroscopic and magnetic evidence of coordination properties of bioactive diethyl (pyridin-4-ylmethyl)phosphate ligand with chloride transition-metal ions

A series of five chloride coordination compounds of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand, i.e. [CuCl₂(4-pmOpe)₂], [NiCl₂(4-pmOpe)₄], [CoCl₂(4-pmOpe)], [ZnCl₂(4-pmOpe)₂], and [CdCl₂(4-pmOpe)₂], was prepared and studied. Stoichiometry and stereochemistry of the compounds was confirmed by spectroscopic and magnetic studies as well as by elemental analyses. The 4-pmOpe ligand has a capacity to coordinate to metal ions by means of phosphoryl oxygen and/or nitrogen of pyridine atoms. In Cu(II), Ni(II), and Zn(II) compounds, 4-pmOpe adopts the monodentate coordination mode, bonding metal centers through the pyridine nitrogen atom only. On the contrary, in Co(II) and Cd(II) compounds, 4-pmOpe acts as N,O-bridging ligand forming polynuclear structures. Magnetic studies (1.8–300 K) indicate mononuclear structure of the Co(II) and Ni(II) compounds and suggest existence of a very weak exchange coupling between metal centers in crystal lattice.