Sulfonamides as ionophores for ion-selective electrodes. IV. New secondary sulfonamide podands and cryptands

New compounds — podands and cryptands with two secondary sulfonamide groups —have been synthesized and are described. They were tested as ionophores for guanidinium ions in PVC-membrane electrodes with bis (2-ethylhexyl)sebacate (DOS) as plasticizer.     

Note on a theoretical interpretation of the isotopic ratio vOH/vOD versus vOH in isotopically diluted HDO molecules in solid hydrates

A simple intra- and inter-molecular potential for water molecules engaged in hydrogen bonding has been used in a one-dimensional approximation for a theoretical interpretation of the experimental correlation $\text{v}$_OH/$\text{v}$_OD versus $\text{v}$_OH in solid hydrates. The variation in the equilibrium OH(D) distance has also been considered.     

Synthesis of 1,3,4,14b-tetrahydro-2H,10H-pyrazino[1,2-α]- pyrrolo[2,1-c][1,4]benzodiazepines

1,3,4,14b-Tetrahydro-2H,10H-pyrazino[1,2-α]pyrrolo[2,1-c] [1,4]benzodiazepines (1a-e) were synthesized to investigate their potential CNS activity. The key step in the synthesis was the formation of the 10,11-dihydro-5H-pyrrolo[2,1-c][1,4]benzodiazepine (13) by reduction and concomitant cyclization of the nitroketone (11). Biological evaluation of 1a-e revealed interesting properties for 1b (CGS 7525A) [2].     

Bonding Properties of a Novel Inorganometallic Complex, Ru(SnPh(3))(2)(CO)(2)(iPr-DAB) (iPr-DAB = N,N'-Diisopropyl-1,4-diaza-1,3-butadiene), and its Stable Radical-Anion, Studied by UV-Vis, IR, and EPR Spectroscopy, (Spectro-) Electrochemistry, and Density Functional Calculations

Ru(SnPh(3))(2)(CO)(2)(iPr-DAB) was synthesized and characterized by UV-vis, IR, (1)H NMR, (13)C NMR, (119)Sn NMR, and mass (FAB(+)) spectroscopies and by single-crystal X-ray diffraction, which proved the presence of a nearly linear Sn-Ru-Sn unit. Crystals of Ru(SnPh(3))(2)(CO)(2)(iPr-DAB).3.5C(6)H(6) form in the triclinic space group P&onemacr; in a unit cell of dimensions a = 11.662(6) ?, b = 13.902(3) ?, c = 19.643(2) ?, alpha = 71.24(2) degrees, beta = 86.91(4) degrees, gamma = 77.89(3) degrees, and V = 2946(3) ?(3). One-electron reduction of Ru(SnPh(3))(2)(CO)(2)(iPr-DAB) produces the stable radical-anion [Ru(SnPh(3))(2)(CO)(2)(iPr-DAB)](*-) that was characterized by IR, and UV-vis spectroelectrochemistry. Its EPR spectrum shows a signal at g = 1.9960 with well resolved Sn, Ru, and iPr-DAB (H, N) hyperfine couplings. DFT-MO calculations on the model compound Ru(SnH(3))(2)(CO)(2)(H-DAB) reveal that the HOMO is mainly of sigma(Sn-Ru-Sn) character mixed strongly with the lowest pi orbital of the H-DAB ligand. The LUMO (SOMO in the reduced complex) should be viewed as predominantly pi(H-DAB) with an admixture of the sigma(Sn-Ru-Sn) orbital. Accordingly, the lowest-energy absorption band of the neutral species will mainly belong to the sigma(Sn-Ru-Sn)-->pi(iPr-DAB) charge transfer transition. The intrinsic strength of the Ru-Sn bond and the delocalized character of the three-center four-electron Sn-Ru-Sn sigma-bond account for the inherent stability of the radical anion.     

A comparative molecular dynamics study of crystalline,paracrystalline and amorphous states of cellulose

The quintessential form of cellulose in wood consists of microfibrils that have high aspect ratio crystalline domains embedded within an amorphous cellulose domain. In this study, we apply united-atom molecular dynamics simulations to quantify changes in different morphologies of cellulose. We compare the structure of crystalline cellulose with paracrystalline and amorphous phases that are both obtained by high temperature equilibration followed by quenching at room temperature. Our study reveals that the paracrystalline phase may be an intermediate, kinetically arrested phase formed upon amorphisation of crystalline cellulose. The quenched structures yield isotropic amorphous polymer domains consistent with experimental results, thereby validating a new computational protocol for achieving amorphous cellulose structure. The non-crystalline cellulose compared to crystalline structure is characterized by a dramatic decrease in elastic modulus, thermal expansion coefficient, bond energies, and number of hydrogen bonds. Analysis of the lattice parameters shows that Iβ cellulose undergoes a phase transition into high-temperature phase in the range of 450–550 K. The mechanisms of the phase transition elucidated here present an atomistic view of the temperature dependent dynamic structure and mechanical properties of cellulose. The paracrystalline state of cellulose exhibits intermediate mechanical properties, between crystalline and amorphous phases, that can be assigned to the physical properties of the interphase regions between crystalline and amorphous cellulose in wood microfibrils. Our results suggest an atomistic structural view of amorphous cellulose which is consistent with experimental data available up to date and provide a basis for future multi-scale models for wood microfibrils and all-cellulose nanocomposites.     

Thermomechanical treatment of two Ecuadorian zeolite-rich tuffs and their potential usage as supplementary cementitious materials

Two Ecuadorian zeolite-rich tuffs, coded as Zeo1 (Mordenite) and Zeo2 (Clinoptilolite–Heulandite–Mordenite), were treated and used as supplementary cementitious materials (SCM) so as to study the effect of the thermal and mechanical treatments on pozzolanic reaction in mortars. The treatment was carried out by means of thermomechanical process according to a central composite-blocked cube-star experimental design. In this experimental design as independent factors the milling time (48, 60, 90, 120 and 132 min) and the heating temperatures (559, 600, 700, 800 and 841 °C) were used but keeping a constant heating time (5 h), and zeolite-rich tuffs as experimental blocks. The proportion of SCM was kept constant i.e. 15 %. On the other hand, the compressive strength, fixed lime, normalized water in hydrates and mg Ca(OH)₂ per mg Cement at 7, 28 and 45 days, as well as hydration products related to dehydration degree of the zeolitic tuffs (DOD) were used as dependent factors. In addition, Quantitative and High-temperature chamber XRD, TG-DSC, particle size distribution and SEM-EDS were also carried out. The most significant factor was calcination leading to increase in the compressive strength compared to control, but just up to 800 °C because of recrystallization. As a conclusion, a meaningful loss of crystal structure of zeolites was not observed; but instead, the treatment could only lead to removing the water in cages and voids, thus improving the reaction with Ca(OH)₂, producing more hydrates. In addition, lime was not only fixed by pozzolanic reaction, but also by carbonation.     

Semi-continuous High Speed Gas Analysis of Generated Vapors of Chemical Warfare Agents

A method is presented for the continuous analysis of generated vapors of the nerve agents soman and sarin and the blistering agent sulfur mustard. By using a gas sampling valve and a very short (15 cm) column connected to an on-column injector with a “standard length” column, the system can either be calibrated or used for performing high speed gas analyses. When using a flame ionization detector, the detection limit was ca. 100 ppb (ca. 0.5–1.0 mg/m³). This technique is applied in inhalation toxicokinetic studies of nerve agents and mustard gas in the guinea pig.     

Properties of monolayers of crown ethers bearing an azo and azoxy group in the macrocycle

Two methods are described for preparing monomolecular layers of crown ethers with an azo or azoxy group in the macrocycle. When the molecules used to build the monolayer are soluble in aqueous solutions, adsorptive preconcentration on mercury electrodes was used to prepare the monolayer coating. The monolayer was electroactive due to the presence of the azo or azoxy unit in the molecules. Monolayers of crown ethers bearing an azo group in the macrocycle were shown to recognize alkali metal cations present in the solution. Changes of the parameters of the voltammetric reduction peaks - peak potential and peak width, served as an indication of specific interactions of the monolayer of 13-membered and 16-membered azocrown ethers with Na⁺ and K⁺ cations, respectively.The monolayers capable of recognizing cations have also been prepared on the aqueous solution-air interface, using the Langmuir technique. In this approach, amphiphilic derivatives of the azocrowns were synthesized and the monolayer has been assembled on the subphase containing metal cations. Binding of the cation by the macrocycle has a stabilizing effect on the monolayer and higher collapse pressures are achieved than on the pure water subphase. The monolayer was transferred from the air-water interface on the solid substrate using the Langmuir-Blodgett technique. Thin mercury film electrodes on the Ag substrate, or An films evaporated on glass slides were employed as the electrode substrates. The former gave monolayer modified electrodes of higher stability.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.