Electronic structure,chemical bonding and X-ray photoelectron spectra of heavy rare-earth oxides

The electronic structure of the heavy RE sesquioxides from Sm₂O₃ to Lu₂O₃ has been studied by the cluster discrete variational X method and X-ray photoelectron spectroscopy. The interpretation of XPS spectra basing on the MO model is given. An analysis of the dependence of Ln 4f orbitals contribution to chemical bonding on the lanthanide atomic number and bond lengths is made.     

Electronic structure of clusters of 3d elements in layered oxide systems

Sverdlovak State Pedagogical Institute. Institute of Chemistry, Ural Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 1, pp. 20–25, January–February, 1991.     

Rauvolfianine,a new antimycobacterial glyceroglycolipid and other constituents from Rauvolfia caffra. Sond (Apocynaceae)

The chemical investigation of the extract of the dried leaves of Rauvolfia caffra (Sond) (synonym Rauvolfia macrophylla) (Apocynaceae) led to isolation of a new glycoside derivative, rauvolfianine (1) as well as six known compounds: oleanolic acid (2), sitosterol-3-O-β-D-glucopyranoside (3), betulinic acid (4), vellosimine (5), sarpagine (6) and D-fructofuranosyl-β-(2→1)-α-D-glucopyranoside (7). Compounds 1, 2, 3, 4 and 7 were evaluated for antitubercular activity. Compounds 1 and 2 were the most active (MIC = 7.8125 and 31.25 μg/mL) towards the Isoniazid resistant strain of Mycobacterium tuberculosis AC45. Their structures and relative stereochemistry were elucidated by spectroscopic methods.     

Mechanistic Study of the Titanocene(III)‐Catalyzed Radical Arylation of Epoxides

An atom‐economical and catalytic arylation of epoxide‐derived radicals is described. The key step of the catalytic system is a sequential electron and proton transfer for the rearomatization of the radical σ‐complex and catalyst regeneration. Kinetic, computational, spectroscopic, and cyclovoltammetric investigations highlight the key issues of the reaction mechanism and catalyst stabilization by collidine hydrochloride. Studies employing radicophiles rule out the participation of cations as reactive intermediates.     

Probing actinide electronic structure through pu cluster calculations

Calculations of the electronic structure of clusters of plutonium have been performed, within the framework of the relativistic discrete‐variational method. These theoretical results and those calculated earlier for related systems have been compared to spectroscopic data produced in the experimental investigations of bulk systems, including photoelectron spectroscopy. Observation of the changes in the Pu electronic structure as a function of size provides powerful insight for aspects of bulk Pu electronic structure. © 2013 Wiley Periodicals, Inc.     

Absorption in the ν3 Band of UF6 Dissolved in Solid Xenon

The ν₃ band of UF₆ isolated in solid xenon is shown to consist of a single sharp spectral feature.     

The Effects of Iron on In Silico Simulated Abiotic Reaction Networks

Iron is one of the most abundant elements in the Universe and Earth’s surfaces, and undergoes a redox change of approximately 0.77 mV in changing between its +2 and +3 states. Many contemporary terrestrial organisms are deeply connected to inorganic geochemistry via exploitation of this redox change, and iron redox reactions and catalysis are known to cause significant changes in the course of complex abiotic reactions. These observations point to the question of whether iron may have steered prebiotic chemistry during the emergence of life. Using kinetically naive in silico reaction modeling we explored the potential effects of iron ions on complex reaction networks of prebiotic interest, namely the formose reaction, the complexifying degradation reaction of pyruvic acid in water, glucose degradation, and the Maillard reaction. We find that iron ions produce significant changes in the connectivity of various known diversity-generating reaction networks of proposed prebiotic significance, generally significantly diversifying novel molecular products by ~20%, but also adding the potential for kinetic effects that could allow iron to steer prebiotic chemistry in marked ways.     

Hydrophobic Cysteine Poly(disulfide)‐based Redox‐Hypersensitive Nanoparticle Platform for Cancer Theranostics

Selective tumor targeting and drug delivery are critical for cancer treatment. Stimulus‐sensitive nanoparticle (NP) systems have been designed to specifically respond to significant abnormalities in the tumor microenvironment, which could dramatically improve therapeutic performance in terms of enhanced efficiency, targetability, and reduced side‐effects. We report the development of a novel L ‐cysteine‐based poly (disulfide amide) (Cys‐PDSA) family for fabricating redox‐triggered NPs, with high hydrophobic drug loading capacity (up to 25 wt % docetaxel) and tunable properties. The polymers are synthesized through one‐step rapid polycondensation of two nontoxic building blocks: L ‐cystine ester and versatile fatty diacids, which make the polymer redox responsive and give it a tunable polymer structure, respectively. Alterations to the diacid structure could rationally tune the physicochemical properties of the polymers and the corresponding NPs, leading to the control of NP size, hydrophobicity, degradation rate, redox response, and secondary self‐assembly after NP reductive dissociation. In vitro and in vivo results demonstrate these NPs’ excellent biocompatibility, high selectivity of redox‐triggered drug release, and significant anticancer performance. This system provides a promising strategy for advanced anticancer theranostic applications.     

Ruthenium‐Grafted Vinylhelicenes: Chiroptical Properties and Redox Switching

The properties of mono‐ and bis‐Ru–vinyl[6]helicene complexes ( 2 a and 2 b , respectively), recently synthesized by using molecular engineering of helicenes based on the grafting of lateral organometallic substituents on the π‐helical backbone through a vinyl bridge, are presented. These helicene derivatives are thoroughly characterized, with special attention given to their chiroptical properties and redox switching activity. The UV/Vis and electronic circular dichroism (ECD) spectra of P and M enantiopure species, both in the neutral and oxidized states ([ 2 a ] ^{. +}, [ 2 b ] ^{. +}, and [ 2 b ]²⁺), are analyzed with the aid of quantum‐chemical calculations. The extended π‐conjugation facilitated by the vinyl moiety, clearly visible in the electronic structures of 2 a , b , introduces new active bands in the ECD spectra that consequently lead to a significant increase in optical rotation of Ru–vinylhelicenes compared with the organic precursors. The vibrational circular dichroism (VCD) spectra were measured and calculated for both the organic and organometallic species and constitute the first examples of VCD for metal‐based helicene derivatives. Finally, the redox‐triggered chiroptical switching activity of 2 a , b is examined in detail by using ECD spectroscopy. The modifications of the ECD spectra in the UV/Vis and NIR region are well reproduced and rationalized by calculations.     

Modulational instability in the cubic-quintic nonlinear Schrödinger equation through the variational approach

The dynamics of nonlinear pulse propagation in an average dispersion-managed soliton system is governed by a constant coefficient nonlinear Schrödinger (NLS) equation. For a special set of parameters the constant coefficient NLS equation is completely integrable. The same constant coefficient NLS equation is also applicable to optical fiber systems with phase modulation or pulse compression. We also investigate MI arising in the cubic-quintic nonlinear Schrödinger equation for ultrashort pulse propagation. Within this framework, we derive ordinary differential equations (ODE’s) for the time evolution of the amplitude and phase of modulation perturbations. Analyzing the ensuing ODE’s, we derive the classical modulational instability criterion and identify it numerically. We show that the quintic nonlinearity can be essential for the stability of solutions. The evolutions of modulational instability are numerically investigated and the effects of the quintic nonlinearity on the evolutions are examined. Numerical simulations demonstrate the validity of the analytical predictions.