Stereochemically controlled synthesis of unsaturated acids via diphenylphosphinoyl (Ph2PO) -ketoacids

Acylation of phosphine oxide anions with derivatives of cyclic anhydrides or oxidative cleavage of cyclic allyl phosphine oxides gives Ph₂PO-ketoacids: reduction, separation of diastereoisomers, and completion of the Horner-Wittig reaction gives single isomers ($\text{E}$) or ($\text{Z}$) of unsaturated acids.     

A role of non-hydrogen framework vibrational modes in formation of ferroelectric properties of H-bonded K3H(SO4)2-like materials

An effect of molecular vibrational modes within the dimers [O₃AO–(H/D)OAO₃]³⁻ on behavior of H-bond protons or deuterons is studied theoretically for H-bonded antiferroelectrics and quantum paraelectrics of the M₃(H/D)(AO₄)₂ family (M=alkali metal, A=S, Se). The ‘heavy’ reorganization modes in D-species of this family and both reorganization and promoting modes in corresponding H-analogues are examined. It is shown that the analysis with due regard for the reorganization modes results in insignificant decreasing of the effective tunneling frequency of light nuclei. Hence the reasonable estimations of the critical temperature of the low-temperature phase transition in M₃D(AO₄)₂ materials are available only with additional corrections related to potential profiles of a deuteron. It is noted that in the limits of the proposed model the promoting mode in the case of H-species can favor, in principle, the increasing as well as the decreasing of effective proton level splitting.     

The adsorption of triethylenediamine on Al(2)O(3)-I: a vibrational spectroscopic and desorption kinetic study of surface bonding

The adsorption of triethylenediamine (TEDA) at 300 K is observed to occur via hydrogen bonding to isolated Al-OH groups on the surface of partially dehydroxylated high area gamma-Al(2)O(3) powder. This form of bonding results in +0.3 to +0.4% blue shifts in the CH(2) scissor modes at 1455 cm(-1) and a -0.4% red shift in the CN skeletal mode at 1060 cm(-1), compared to the gas-phase frequencies. Other modes are red shifted less than 0.1%. The isolated OH modes are red shifted by -200 to -1000 cm(-1) due to the strong hydrogen bonding association of Al-OH groups with an N atom in TEDA. Thermal desorption of adsorbed TEDA from the surface occurs in the range 300-700 K. Mass spectral and infrared studies indicate that the decomposition of TEDA occurs on Al(2)O(3) above 725 K, and that C-H bonds are broken, forming adsorbed species with N-H bonds which are stable to 1000 K or above. In contrast to adsorption at 300 K, adsorption of TEDA at 85 K results in the formation of a condensed ice of TEDA, which covers the outer surface of the porous Al(2)O(3) and which does not interact with Al-OH groups inside the porous powder due to immobility.     

Triplet states of humic acids studied by laser flash photolysis using different excitation wavelengths

The spectra and kinetics of short-lived intermediates formed from aqueous (0.1 N NaOH) solutions of the natural mixture of humic and fulvic acids (HFA) were studied by laser flash photolysis using excitation wavelengths of 337, 390, 470, and 520 nm. Laser photolysis of HFA with light of 520 and 470 nm results in the formation of triplet excited states (T_HFA) characterized by the broad absorption spectrum with a maximum near 630 nm and lifetimes of 0.15 ms in deoxygenated solutions. The formation of two types of T_HFA with lifetimes of 0.1 and 2 ms and absorption spectra with maxima at 570 nm is observed under photolysis with light of 337 and 390 nm. The estimation of quantum yields of T_HFA gives 1 and 0.3% under photolysis with excitation wavelengths of 337 and 520 nm, respectively. The rate constants of T_HFA quenching by molecular oxygen are equal to (7—8)·10⁸ L mol^–1 s^–1.     

Structural, textural, and electronic properties of a nanosized mesoporous ZnxTi1-xO2-) solid solution prepared by a supercritical drying route

Mesoporous nanosized TiO2 and Zn(x)Ti(1-x)O(2-x) solid solution having a Zn content below 10 mol % with a particles size between 13 and 17 nm are prepared by a template-free sol-gel method followed by high-temperature supercritical drying in 2-propanol. The structural, textural, and electronic properties of the obtained nanomaterials are methodically investigated by using XRD, SEM, TEM, ED, HREM, EDX, ICP-OES, N(2) adsorption-desorption, Raman spectroscopy, and diffuse reflectance UV-vis spectroscopy. It is shown that the proposed synthesis technique leads to the formation of a Zn(x)Ti(1-x)O(2-x) solid solution based on the anatase crystal structure rather than a two-phase sample. High-resolution electron microscopy and electron diffraction indicate that the distribution of zinc atoms over the anatase structure does not lead to a considerable deformation of the crystal structure.