Coexisting antiferromagnetism and ferromagnetism in mechanically alloyed Fe-rich Fe–Ni alloys: implications regarding the Fe–Ni phase diagram below 400°C

Fe–Ni alloys below the Invar region with compositions Fe_100−xNi_x (x=21, 24, and 27 at%) were prepared by high-energy ball milling technique (mechanical alloying). The as-milled samples, characterized by X-ray diffraction and Mössbauer spectroscopy, contain a mixture of (BCC) and γ (FCC) phases, whereas the samples annealed at 650°C for 0.5 h show a single γ (FCC) phase displaying a single line Mössbauer spectrum at room temperature (RT). At low temperature, the Mössbauer spectra of annealed Fe₇₆Ni₂₄ and Fe₇₃Ni₂₇ alloys show the existence of a magnetically split pattern together with a broad singlet, which are ascribed to a high-moment ferromagnetic Ni-rich phase and a low-moment Fe-rich phase, respectively. The Fe-rich phase in annealed Fe₇₆Ni₂₄ alloy, which is paramagnetic at RT, undergoes antiferromagnetic ordering at 40 K, estimated from the dramatic line broadening of its spectrum, giving rise to a small hyperfine field (e.g. 2 T at 6 K). The coexistence of these phases is attributed to phase segregation occurring in these alloys as a result of enhanced atomic diffusion. The stability of these alloys towards martensitic (FCC→BCC) transformation at low temperatures is discussed in connection with the Fe–Ni phase diagram below 400°C.     

Some novel photosensitive diacetylene diurethanes and their mixtures in common polymers

Some new octa-3,5-diynylene diurethanes were prepared using 3-butyn-1-ol, and all were found to be highly light-sensitive and to undergo topochemical polymerization on exposure to irradiation. The di-n-octyldiurethane was mixed with vinyl polymers such as poly(vinyl acetate) and poly(N,N-dimethylamino-ethyl methacrylate) and the mixtures were made into thin films by spin coating. The films were then irradiated by an electron beam to polymerize the diacetylene. The purple films thus obtained showed third-order nonlinear susceptibility, χ⁽³⁾, of the order of 10⁻¹⁰–10⁻¹¹ e.s.u.     

A simple flow injection spectrophotometric determination method for iron(III) based on O-acetylsalicylhydroxamic acid complexation

A simple and rapid flow-injection spectrophotometric method for the determination of iron(III) and total iron is proposed. The method is based on the reaction between iron(III) and O-acetylsalicylhydroxamic acid (AcSHA) in a 2 % methanol solution resulting in an intense violet complex with strong absorption at 475 nm. Optimum conditions for the determination of iron(III) and the interfering ions were tested. The relative standard deviation for the determination of 5 μg L⁻¹ iron(III) was 0.85 % (n = 10), and the limit of detection (blank signal plus three times the standard deviation of the blank) was 0.5 μg L⁻¹, both based on the injection volumes of 20 μL. The method was successfully applied in the determination of iron(III) and total iron in water and ore samples. The method was verified by analysing a certified reference material Zn/Al/Cu 43XZ3F and also by the AAS method.     

Structural properties of new spiro-1,3-propanediaminocyclotriphosphazene derivatives

New 1,3-propanediaminocyclotriphosphazene derivatives (7-17) were synthesized from the reactions of spiro-1,3-propanediaminocyclotriphosphazene, N₃P₃Cl₄[NH(CH₂)₃NH] (1) with the cyclopropanemethylamine (2), cyclohexylamine (3), pyrrolidine (4) cyclohexanol (5), cyclopropylmethanol (6). The structures of the novel compounds (7-17) were characterized by elemental analysis, mass spectrometry, ¹H and ³¹P NMR spectroscopy. The molecular structures of 8, 12 and 13 were determined by X-ray crystallography. The structures of all these three compounds are in the monoclinic crystal system; compounds 8 and 12 have the P21/c space group while compound 13 has the P21/n space group. The ring conformation of the cyclotriphosphazene and other external rings were investigated based on the X-ray crystal structures.     

Synthesis,Antibacterial, and Antioxidant Evaluation of Novel Series of Condensed Thiazoloquinazoline with Pyrido,Pyrano, and Benzol Moieties as Five- and Six-Membered Heterocycle Derivatives

A novel synthesis of thiazolo[2,3-b]quinazolines 4(a–e), pyrido[2′,3′:4,5]thiazolo[2,3-b]quinazolines {5(a–e), 6(a–e), and 7(a–e)}, pyrano[2′,3′:4,5]thiazolo[2,3-b]quinazolines 8(a–e), and benzo[4,5]thiazolo[2,3-b]quinazoloine9(a–e) derivatives starting from 2-(Bis-methylsulfanyl-methylene)-5,5-dimethyl-cyclohexane-1,3-dione 2 as efficient α,α dioxoketen dithioacetal is reported and the synthetic approaches of these types of compounds will provide an innovative molecular framework to the designing of new active heterocyclic compounds. In our study, we also present optimization of the synthetic method along with a biological evaluation of these newly synthesized compounds as antioxidants and antibacterial agents against the bacterial strains, like S. aureus, E. coli, and P. aeruginosa. Among all the evaluated compounds, it was found that some showed significant antioxidant activity at 10 μg/mL while the others exhibited better antibacterial activity at 100 μg/mL. The results of this study showed that compound 6(c) possessed remarkable antibacterial activity, whereas compound 9(c) exhibited the highest efficacy as an antioxidant. The structures of the new synthetic compounds were elucidated by elemental analysis, IR, ¹H-NMR, and ¹³C-NMR.     

Intermolecular interactions in nitrogen-containing aromatic systems

π–π and CH···N interactions are vital in biological systems. In this study, stacking and hydrogen-bonded interactions in pyrazine and triazine dimers were investigated by density functional theory combined with symmetry-adapted perturbation theory (DFT-SAPT) and counterpoise (CP)-corrected supermolecular MP2, SCS-MP2, B3LYP-D and CCSD(T) calculations. All interaction energies were computed using the optimized structures at the CP-corrected SCS/aug-cc-pVDZ level, which gave 1–2 kJ/mol lower interaction energies than the ones computed at the MP2 level. For both dimers, doubly hydrogen-bonded and cross-(displaced) stacked orientations were found to be the lowest energy ones. The reference CCSD(T) calculations favored the former structure in both dimer systems, whereas MP2 and SCS-MP2 located the latter as the lowest energy isomer. In particular, the former was found to be lower in energy than the latter by 2.28 and 1.01 kJ/mol at the CCSD(T)/aug-cc-pVDZ level for pyrazine and triazine, respectively. B3LYP-D produced interaction energies in agreement with the CCSD(T) at the equilibrium geometries, but it overestimates them at the short range and underestimates at the long intermonomer separations. Furthermore, it tends to give smaller equilibrium distances compared to the CCSD(T). DFT-SAPT method was in a good agreement with the reference CCSD(T) calculations. This suggests that DFT-SAPT can be employed to compute the full potential energy surface of these dimers. Moreover, DFT-SAPT calculations showed that the electrostatic and dispersion contributions are the most important energy components stabilizing these dimers. The present study aims to show which theoretical method is the most promising one for the investigation of intermolecular interactions dominated by π–π and CH···N. Therefore, the findings obtained in this study can be used to unravel the structures of nucleic acid bases and other systems stabilized by π–π and CH···N interactions.     

Conversion of a cyclotriphosphazene to a cyclohexaphosphazene by ring expansion

Deprotonation of a cyclotriphosphazene with a tert-butylamino group in the side chain results in ring expansion to a very stable, planar cyclohexaphosphazene derivative that still contains eight P-Cl bonds suitable for forming macromolecular structures.