DFT study of structure–properties correlations in [MnTPP][TCNE] quasi-one-dimensional molecular magnets

We report the first band structure calculations of the quasi-one-dimensional [MnTPP][TCNE] compounds (TPP = meso-tetraphenylporphyrinato, TCNE = tetracyanoethylene), based on Density Functional Theory (DFT) methods, in order to interpret the magnetic ordering in these prototypic systems. We compare and contrast the results of broken-symmetry DFT calculations for extended systems, with periodic boundary conditions, and for finite systems, magnetic dimers modeling the actual molecular magnets. By varying systematically the main angles, we are able to determine the geometry dependence of the exchange interaction. Structure–properties correlations in these charge-transfer salts reveal the determinant role of the Mn-(N≡C)_TCNE bond angle on the strength of the ferrimagnetic coupling between the S ₁ = 2 spin located on the Mn^III-porphyrin donor and the S ₂ = 1/2 spin positioned on the cyanocarbon acceptor. When the Mn-(N≡C)_TCNE angle is decreased, the intrachain magnetic coupling strengthens, correlated with the increase in the d_z² - p* d_{{z^{2} }} - \pi * orbital overlap. The exchange coupling constants resulting from DFT calculations of extended systems, with periodic boundary conditions, were found to be consistent with those obtained for the dimers, but systematically smaller. The exchange constants vary strongly with the functional used, hybrid functionals such as B3LYP leading to results that better correlate with the experimental mean-field critical temperatures. The coupling constant varies significantly with the type of broken-symmetry approach, depending on the overlap between magnetic orbitals, but weakly on the basis set once polarization effects are included. The electronic structure calculations for the extended systems provide a density of states consistent with the energy spectrum of the corresponding dimer, allowing for an intuitive explanation of the intrachain ferrimagnetic ordering.     

Synthesis and photophysical properties of some 6,6″-functionalized terpyridine derivatives

The synthesis and photophysical properties of several 6,6″ symmetrically substituted 4′-aryl-2,2′:6′,2″-terpyridine derivatives are reported herein. The UV-Vis spectra in acetonitrile as well as in dichloromethane show two intense bands in the UV areas 252–262 nm and 275–290 nm while the fluorescence emission spectra are only slightly influenced by chemical derivatization.     

Assessment of the In Vivo Release and Biocompatibility of Novel Vesicles Containing Zinc in Rats

This paper is focused on the in vivo release and biocompatibility evaluation in rats of some novel systems entrapping zinc chloride in lipid vesicles. The particles were prepared by zinc chloride immobilization inside lipid vesicles made using phosphatidylcholine, stabilized with 0.5% chitosan solution, and dialyzed for 10 h to achieve a neutral pH. The submicrometric systems were physico-chemically characterized. White Wistar rats, assigned into four groups of six animals each, were treated orally with a single dose, as follows: Group I (control): deionized water 0.3 mL/100 g body weight; Group II (Zn): 2 mg/kg body weight (kbw) zinc chloride; Group III (LV-Zn): 2 mg/kbw zinc chloride in vesicles; Group IV (LVC-Zn): 2 mg/kbw zinc chloride in vesicles stabilized with chitosan. Haematological, biochemical, and immune parameters were assessed after 24 h and 7 days, and then liver fragments were collected for histopathological examination. The use of zinc submicrometric particles—especially those stabilized with chitosan—showed a delayed zinc release in rats. No substantial changes to blood parameters, plasma biochemical tests, serum complement activity, or peripheral neutrophils phagocytic capacity were noted; moreover, the tested substances did not induce liver architectural disturbances. The obtained systems provided a delayed release of zinc, and showed good biocompatibility in rats.     

Surface Analysis of Inhibitor Film Formed by 4-Amino-N-(1,3-thiazol-2-yl) Benzene Sulfonamide on Carbon Steel Surface in Acidic Media

Inhibitive properties of the antibacterial sulfa drug sulfathiazole—IUPAC name being 4-amino-N-(1,3-thiazol-2-yl) benzene sulfonamide—on the corrosion of carbon steel in 1.0 M HCl solution were investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Sulfathiazole is a good adsorption inhibitor, and the inhibition efficiency increases with increasing concentration. Adsorption is spontaneous and is best described by Temkin isotherm. XPS analysis showed, at this stage, that the main product of corrosion is a nonstoichiometric Fe³⁺ oxide/oxyhydroxide consisting of a mixture of Fe₂O₃, α, and γ-FeO(OH) and/or Fe(OH)₃, where α, γ-FeO(OH) is the main phase.     

A pulse sequence for averaging the strong homonuclear scalar coupling in AB spin systems

A pulse sequence is proposed for the suppression of the strong homonuclear scalar coupling in the case of AB spin systems. The theoretical treatment is presented in terms of the average Hamiltonian theory in the case of aperiodic perturbations. The zero-order and the first-order correction terms in the full average Hamiltonian are calculated. It is shown that the chemical shift interaction for one of the spins is completely refocused and the conditions in which the interactions bilinear in spin operators are efficiently suppressed are analyzed.     

Travelling waves for reaction-diffusion equations with time depending nonlinearities

The existence of travelling wave with given end points for parabolic system of nonlinear equations is proven. The nonlinear term depends also on a·x−ct where x is the multidimensional space variable, t—time, c—the speed of the wave and a—the direction of travel.     

Accelerated iterative strategy for the divergent synthesis of dendritic macromolecules using a combination of living radical polymerization and an irreversible terminator multifunctional initiator

Our laboratory has reported the elaboration of an iterative strategy for the synthesis of dendritic macromolecules from conventional monomers. This synthetic method involves a combination of self‐regulated metal‐catalyzed living radical polymerization initiated from arenesulfonyl chlorides and an irreversible terminator multifunctional initiator (TERMINI). The previous TERMINI, (1,1‐dimethylethyl)[[1‐[3,5‐bis(S‐phenyl‐4‐N,N′ diethylthiocarbamate)phenyl]ethenyl]oxy]dimethylsilane, was prepared in nine reaction steps. The replacement of the previous TERMINI with one that requires only three steps for its synthesis, diethylthiocarbamic acid S‐{3‐[1‐(tert‐butyl‐dimethyl‐silanyloxy)‐vinyl]‐5‐diethylcarbamoylsulfanyl‐phenyl} ester, and the use of the more reactive Cu₂S/2,2′‐bipyridine rather than the Cu₂O/2,2′‐bipyridine self‐regulated catalyst have generated an accelerated method for the synthesis of dendritic macromolecules. This method provides rational design strategies for the synthesis of dendritic macromolecules with different compaction by the use of a single monomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4894–4906, 2005     

Reaction of 3-acylamino- and 3-alkoxybenzo[<Emphasis Type="Italic">c</Emphasis>]pyrilium salts with hydrazine

The reaction of 3-acylamino- and 3-alkoxybenzo[c]pyrilium perchlorates with hydrazine has been studied. It was discovered that the direction of the recyclization of the pyran ring depends on the type of substituent in position 3 and on the ratio of reactants. Derivatives of isoquinoline and benzo-2,3-diazepine were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.10, pp. 1507–1511, October, 2004.     

The Woods-Saxon wave functions and the beta transitions of deformed nuclei

The general expressions for the beta transition matrix elements have been obtained using the Woods-Saxon wave functions for deformed nuclei proposed byFaessler andSheline. As an application the matrix elements for the 1^?(β^?)0⁺ and 1^?(β^?)2⁺ transitions of the¹⁷⁰Tm nucleus have been calculated. The results indicate significant differences between the Nilsson and Woods-Saxon values of the nuclear parameters. Assuming a reasonableK=0 mixture in the ground state of the¹⁷⁰Tm nucleus and a value near the Ahrens-Feenberg estimate for the ∫ α¦ ∫ir ratio it is possible to obtain an important improvement of the theoretical values of the relevant observables and especially of theft values.     

Characterization of anomeric differences of ammonium-bound monomeric and dimeric complex ions of 1α- and 1β-azido-pentofuranosyl derivates by kinetic method

Relative stabilities (ΔG^c) of ammonium-bound monomers and dimers of anomeric β- -pentofuranosyl 1α- and 1β-azide derivates are determinate using the kinetic method by measuring relative rates of competitive collision-induced dissociations of dimeric [ANH₄B]⁺ and trimeric [A₂NH₄B]⁺ or [ANH₄B₂]⁺ cluster ions. Comparison between calculated ammonium affinities (AAs) and relative stabilities (ΔG^c) of ammonium-bound monomers shows qualitative correlations between both thermochemical quantities, but in two examples the activation barrier differences of competitive fragmentation channels cause a large disparity between both thermochemical data. Therefore, the most stable ammonium-bound monomers of the anomeric lα- and lβ-2,3,5-tri-O-benzyl-β- -arabino-pento-furanosyl azides possess the lowest ammonium affinities and the highest relative stabilities. Two different relative stabilities measured for the same ammonium-bound homo- or hetero-dimers indicate dissimilar activated barriers of trimers transition states for dimer formations. The activated barriers of trimers depend on the relative stabilities of ammonium-bound monomer within the trimeric cluster ions.