Formation Thermodynamics of Binary and Ternary Lanthanide(III) Complexes with 1,10-Phenanthroline and Chloride in N,N-Dimethylformamide

Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethyl-formamide (DMF) containing 0.2 mol-dm^–3 (C₂H₅)₄NClO₄ as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)³⁺ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)³⁺ decrease in the order La > Ce > Nd, then increase in the order Nd < Eu < Gd < Dy, and again decrease in the order Dy > Tm > Lu. The variation is explained in terms of the coordination structure of Ln(phen)³⁺ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln³⁺-Cl^–-phen system, the formation of LnCl(phen)²⁺, LnCl₂(phen)⁺, and LnCl₃(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.     

Study of SPG membrane emulsification processes for the preparation of monodisperse core-shell microcapsules

Experimental investigations on the Shirasu-porous-glass (SPG)-membrane emulsification processes for preparing monodisperse core-shell microcapsules with porous membranes were carried out systematically. The results showed that, to get monodisperse oil-in-water (O/W) emulsions by SPG membrane emulsification, it was more important to choose an anionic surfactant than to consider hydrophile-lipophile balance (HLB) matching. Increasing the viscosity of either the disperse phase or the continuous phase or decreasing the solubility of the disperse phase in the continuous phase could improve both the monodispersity and the stability of emulsions. With increasing monomer concentration inside the disperse phase, the monodispersity of emulsions became slightly worse and the mean diameter of emulsions gradually became smaller. Monodisperse monomer-containing emulsions were obtained when the SPG membrane pore size was larger than 1.0 micro m, and from these emulsions satisfactory monodisperse core-shell microcapsules with a porous membrane were prepared. On the other hand, when the SPG membrane pore size was smaller than 1.0 mciro m, no monodisperse emulsions were obtained because of the formation and chokage of solid monomer crystals in the pores or at the end of the pores of the SPG membrane. This was due to the remarkable solvation and diffusion of the solvent in water. With increasing the emulsification time the average emulsion diameter generally decreased, and the monodispersity of the emulsions gradually became worse.     

Novel synthesis and properties of 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate: autorecycling oxidation of some alcohols under photo-irradiation

Three-step reactions starting from 2-chlorotropone with barbituric acid afforded novel 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (9·BF₄⁻), which is the isoelectronic compound of the 5-ethyl-3-methyllumiflavinium ion. The stability of cation 9 is expressed by the pK_R+ value, which was determined spectrophotometrically, as ca. 6.0. The electrochemical reduction of 9 exhibited low reduction potential at −0.58 (V vs Ag/AgNO₃), upon cyclic voltammetry (CV). In a search for the reactivity, reactions of 9·BF₄⁻ with some nucleophiles, hydroxide, hydride, amines, thiols, and methanol, were carried out to exhibit that the introduction of nucleophiles is dependent on the nucleophile itself. The photo-induced oxidation reactions of some alcohols catalyzed by 9·BF₄⁻ under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compound 9·BF₄⁻], suggesting the oxidizing function of 9·BF₄⁻ toward alcohols in the autorecycling process. The UV-vis and fluorescence spectra of 9 were studied to suggest the electron transfer from alcohols to the excited 9.     

Novel synthesis, static and dynamic properties, and structural characteristics of 5-cyano[n](2,4)pyridinophane-6-ones (n= 9-6) and their chemical transformations

A novel synthesis of 5-cyano[n](2,4)pyridinophane-6-ones 12a-d (n= 9, 8, 7, and 6) consists of allowing cyanoacetatoamide to react with cycloalk-2-enones. Their static and dynamic properties as well as structural characteristics are studied on the basis of their spectroscopic properties, cyclic voltammetry, and theoretical calculations. The (1)H and (13)C NMR spectra at various temperatures have clarified the dynamic behavior of the methylene chains for [7](2,4)- and [6](2,4)pyridinophane-6-one derivatives 12c and 12d. The energy barrier (Delta G(++)) of the bridge flipping of 12c is estimated to be 12.0 kcal mol(-1)(T(c)= 0 degree C). On the other hand, compound 12d undergoes pseudorotation (conformational change of the methylene chain) at room temperature, and does not undergo bridge flipping even at 150 degree C in DMSO-d(6). The energy barrier (Delta G(++)) of the pseudorotation of the methylene chain 12d of is found to be 10.5 kcal mol(-1)(T(c)=-25 degree C), and thus, two stable conformers of the hexamethylene bridge of 12d are determined as predicted by theoretical calculations. Deformation of the pyridone ring of 12d is also determined by X-ray crystallographic analysis. Furthermore, chemical transformations of 12a-c leading to 5-carbamoyl[n](2,4)pyridinophanes 15a-c are also accomplished successfully in moderate to good yields.     

Synthesis of Bis(phosphanyl)alkane Monosulfides by the Addition of Diphosphane Monosulfides to Alkenes under Light

Bis-phosphanated compounds are regarded as the most ubiquitous privileged ligand structures in transition-metal catalysis. The development of highly atom economical reactions is of great importance for their syntheses because less atom economical methods often require complicated purification procedures under inert atmospheres to remove excess starting materials and byproducts. Herein, the photoinduced addition reactions of diphosphane monosulfides bearing P^V(S)−P^III single bonds to alkenes is disclosed. These reactions require only equimolar amounts of the diphosphane monosulfide relative to the alkene and facilitate highly selective introduction of two different types of phosphorus-containing groups, such as thiophosphoryl and phosphanyl groups, into a variety of alkenes without any catalyst, base, or additive.     

Thiol-terminated hydroxy-functional polymer as a transtab toward polymer latex particles

Hydroxy-functional macrodisulfides have been synthesized by atom transfer radical polymerization of 2-hydroxyethyl methacrylate or 2-hydroxypropyl methacrylate in 2-propanol. Mean degrees of polymerization of the polymer chains beside the disulfide were fixed at 30, 60, and 90; since ATRP has reasonably good living character, the molecular weight distribution is relatively narrow. Furthermore, the macrodisulfides were reduced to synthesize corresponding thiol-terminated polymers with relatively narrow molecular weight distributions. ¹H nuclear magnetic resonance and gel permeation chromatography were used to characterize the macrodisulfides and thiol-terminated polymers in terms of their chemical structure, molecular weight, and polydispersity, respectively. Dispersion polymerizations of styrene using the thiol-terminated hydroxy-functional polymers as a transtab (chain transfer agent + colloidal stabilizer) in ethanol resulted in colloidally stable submicrometer-sized polystyrene latex particles. Scanning electron microscopy, Fourier transform infrared spectroscopy, and elemental microanalysis were used to characterize the particles in terms of their morphologies, particle sizes and their distributions, and chemical compositions.     

Combustion behaviors of isolated n-decane and ethanol droplets in carbon dioxide-rich ambience under microgravity

The burning and sooting behaviors of isolated fuel droplets for ethanol and n-decane are examined in high concentration of the ambient carbon dioxide under microgravity. A quartz fiber with the diameter of 50 μm maintains the droplet in the center of the combustion chamber and the range in the initial droplet diameter is from 0.30 to 0.80 mm. The ambience consists of oxygen, nitrogen and carbon dioxide. The concentration of oxygen is 21% in volume, and that of carbon dioxide is varied from 0% to 60% in volume. Detail measurements of the projected image of the droplet are conducted by using a high speed video camera and the effective droplet diameter squared are calculated from the surface area of the rotating body of the projected object. From evolutions of the droplet diameter squared, the instantaneous burning rates are calculated. Time history of the instantaneous burning rate clearly represents the droplet combustion events, such as the initial thermal expansion, ignition and following combustion. The instantaneous burning rate for n-decane shows an increasing trend during combustion, while that for non-sooting ethanol remains almost constant or shows a decreasing trend. A slight stepwise increase in the instantaneous burning rate is observed for larger n-decane droplets in air, which may be attributed to soot accumulation. However, this behavior of the burning rate disappears in higher concentration of carbon dioxide. Direct observation of the droplet flame indicates suppression of soot production in higher concentration of carbon dioxide and the suppression is enhanced for smaller droplet.     

UV–vis and fluorescence detection by receptors based on an isophthalamide bearing a phenylethynyl group

We have successfully prepared 5-(2-phenylethynyl)isophathalilc acid as a signaling unit and the corresponding derivatives for an anion receptor 2 and a barbiturate receptor 4. Receptor 2 showed characteristic UV–vis changes and dramatic fluorescence quenching upon the addition of anions and receptor 4 showed UV–vis and an OFF-ON fluorescence changes upon the addition of dibutylbarbituric acid based on the diphenylethyne moiety.