Heteroanthracyclines-III: 6,7,11-tri-O-methyl-4-demethoxy-12-sulfonodaunomycinone [6,10,11-trimethoxy-8-hydroxy-8-acetyl 7,8,9,10-tetrahydrobenzo(B)-thioxanthen-12-one-5-dioxide

The sulfone analogue of 6,7,11-tri-O-methyl-4-demethoxydaunomyacinone, namely 6,7,11-tri-O-methyl-4-demethoxy-12-sulfonodaunomycinone (12) was synthesized using 5,8-dimethoxy-2-acetyltetralin (13) as starting material which can be prepared in large scale by hydrogen chloride catalysed cyclization of 3- (2,5-dimethoxybenzyl)-l,4-dioxopent shortening and simplifying our earlier procedures and eliminating the handling of large quantity of liquid hydrogen fluoride. The intermediate 15 can be easily prepared in large scale according to the procedure which we reported earlier.^13c Reaction of 13 with 2,2'-dithiosalicylic acid gave an isomeric mixture of 17 and 18 which were separated and their structure differentiated by dipole moment studies¹⁴ Isomer 17 was reduced by Zn dust to 22 and 23 which reacted with anhydrous methanol to form 24 and 25. Both 24 and 25 as an isomeric mixture were oxidized to 28 and29 by oxygen in basic N,N-dimethylformamide solution and finally to the stable sulfones 30 and 31 by m-chloroperoxybenzoic acid. These two isomeric sulfones were separated and fully characterized and then oxidized further to form 34 which was converted to the title compound 12 by free radical bromination and reaction with anhydrous methanol in the presence of silver trifluoromethanesulfonate. The structure of 12 was positively established by detailed analysis of its high field PMR spectrum (Fig. 1)     

Use of hydride generation-atomic absorption spectrometry to determine the effects of hard ions, iron salts and humic substances on arsenic sorption to sorghum biomass

At present, there is a great interest in studying new sorbent materials for the removal of arsenic from aqueous solutions because of its high toxicity and adverse effects on human health. In previous research, sorghum biomass was found to be an efficient and economic sorbent for the removal of arsenic from aqueous solutions. In this investigation, the effects of CaCl₂, MgCl₂, FeSO₄, MgSO₄, Fe(NO₃)₃, and humic substances (peat moss, humin and humic acids) on arsenic binding to sorghum biomass were evaluated. Among these compounds, only iron salts were found to positively increase the sorption of arsenic to sorghum biomass. In addition, the sorption equilibrium was reached faster when the reaction mixture contained iron salts. However, an overall reduction of 21% of arsenic sorption to sorghum biomass was observed in the presence of MgSO₄. This interference may be due to the presence of sulfate ions, instead of the hard cations, that could be in competition with As for the same interaction sites or ligands. Peat moss, humins and humic acid, extracted from sphagnum peat moss, significantly decreased the arsenic sorption to sorghum biomass.     

Transient fieldg-factor measurement of the first 3− state in144Sm

The g-factor of the octupole vibrational state 3⁻ at 1810 keV in¹⁴⁴Sm has been measured to be 0.76(9) by means of the transient field technique. The state has been Coulomb excited by 217 MeV⁵⁸Ni beam. The obtained value agrees with the predictions of RPA calculations and confirms the dominance of the proton particle-hole configuration π(1h_11/2−2d_5/2 ⁻¹)     

Synthesis,structural, and spectral studies of diorganotin(IV) complexes with 2–hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone

Three new diorganotin(IV) complexes, [Me₂Sn(L)] (2), [Bu₂Sn(L)] (3), and [Ph₂Sn(L)] (4) [where H₂L (1) = 2-hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone] have been synthesized by reacting the corresponding diorganotin(IV) dichloride with H₂L (1) in absolute methanol in the presence of potassium hydroxide. All the compounds have been characterized by CHN analyses, UV–vis, FT-IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. The molecular structures of H₂L (1) and 2 have been confirmed by single crystal X-ray diffraction analysis. H₂L (1) is found to be in the thiol tautomeric form. The X-ray structure of 2 showed that H₂L is a tridentate ligand and binds to the tin(IV) atom via the phenolic oxygen, azomethine nitrogen, and thiolate sulfur. Complex 2 has a triclinic structure and the coordination geometry of tin(IV) is distorted trigonal bipyramidal. The sulfur and oxygen are in axial positions while the azomethine nitrogen of 1 and two methyl groups occupy the equatorial positions. The C-Sn-C angles determined from ¹J(¹¹⁹Sn, ¹³C) for 2, 3, and 4 are 124.35°, 123.11°, and 123.82°, respectively. The values of δ(¹¹⁹Sn) for 2, 3, and 4 are ?153.4, ?180.59, and ?158.3 ppm, respectively, indicating five-coordinate tin(IV). From NMR data a distorted trigonal-bipyramidal configuration at each tin is proposed.     

Trapped fermionic clouds distorted from the trap shape due to many-body effects

We present a general approach for describing trapped Fermi gases, when the cloud shape is distorted with respect to the trap shape. Our approach provides a consistent way to explore physics beyond the local density approximation, if this is necessary due to the distortion. We illustrate this by analyzing in detail experimentally observed distortions in a trapped imbalanced Fermi mixture. In particular, we demonstrate in that case dramatic deviations from ellipsoidal cloud shapes arising from the competition between surface and bulk energies.     

The Role of Oxygen in the Degradation of Methylammonium Lead Trihalide Perovskite Photoactive Layers

In this paper we report on the influence of light and oxygen on the stability of CH₃NH₃PbI₃ perovskite‐based photoactive layers. When exposed to both light and dry air the mp‐Al₂O₃/CH₃NH₃PbI₃ photoactive layers rapidly decompose yielding methylamine, PbI₂, and I₂ as products. We show that this degradation is initiated by the reaction of superoxide (O₂^?) with the methylammonium moiety of the perovskite absorber. Fluorescent molecular probe studies indicate that the O₂^? species is generated by the reaction of photoexcited electrons in the perovskite and molecular oxygen. We show that the yield of O₂^? generation is significantly reduced when the mp‐Al₂O₃ film is replaced with an mp‐TiO₂ electron extraction and transport layer. The present findings suggest that replacing the methylammonium component in CH₃NH₃PbI₃ to a species without acid protons could improve tolerance to oxygen and enhance stability.     

Error bounds on the SCISSORS approximation method

The SCISSORS method for approximating chemical similarities has shown excellent empirical performance on a number of real-world chemical data sets but lacks theoretically proven bounds on its worst-case error performance. This paper first proves reductions showing SCISSORS to be equivalent to two previous kernel methods: kernel principal components analysis and the rank-k Nystro?m approximation of a Gram matrix. These reductions allow the use of generalization bounds on these techniques to show that the expected error in SCISSORS approximations of molecular similarity kernels is bounded in expected pairwise inner product error, in matrix 2-norm and Frobenius norm for full kernel matrix approximations and in root-mean-square deviation for approximated matrices. Finally, we show that the actual performance of SCISSORS is significantly better than these worst-case bounds, indicating that chemical space is well-structured for chemical sampling algorithms.