Tetrameric triphenylsilanol, (Ph3SiOH)4, and the adduct (Ph3SiOH)2–di­methyl sulfoxide,both at 120 K,and the adduct (Ph3SiOH)4–1,4‐dioxan at 150 K: interplay of O—H⋯O and C—H⋯π(arene) interactions

The structure of tetrameric tri­phenyl­silanol, C₁₈H₁₆OSi, (I), has been re‐investigated at 120 (2) K. The hydroxyl H atoms were readily located and one of the arene rings is disordered over two closely positioned sets of sites. The mol­ecules are linked into cyclic tetramers, having approximate (S₄) symmetry, via O—H?O hydrogen bonds [H?O 1.81–1.85 Å, O?O 2.634 (3)–2.693 (3) Å and O—H?O 156–166°]. At ambient temperature, there are indications of multiple disorder of the phenyl‐ring sites. In bis­(tri­phenyl­silanol) di­methyl sulfoxide solvate, 2C₁₈H₁₆OSi·C₂H₆OS, (II), the di­methyl sulfoxide component is disordered across a twofold rotation axis in C2/c, and the molecular components are linked by a single O—H?O hydrogen bond [H?O 1.85 Å, O?O 2.732 (2) Å and O—H?O 172°] into three‐mol­ecule aggregates, which are themselves linked into a single three‐dimensional framework by two C—H?π(arene) interactions. In tetrakis­(tri­phenyl­silanol) 1,4‐dioxan solvate, 4C₁₈H₁₆OSi·C₄H₈O₂, (III), the 1,4‐dioxan component lies across an inversion centre in space group P and centrosymmetric five‐mol­ecule aggregates are linked by paired C—H?π(arene) interactions to form molecular ladders.     

meso‐5,5,7,12,12,14‐Hexamethyl‐1,4‐diaza‐8,11‐diazoniacyclotetradecane bis(2‐naphthoate) ethanol disolvate: centrosymmetric five‐component aggregates linked into sheets by C—H⃛π(arene) hydrogen bonding

The title compound is an ethanol‐solvated salt, C₁₆H₃₈N₄²⁺·2C₁₁H₇O₂⁻·2C₂H₆O, in which the cation lies across a centre of inversion in P2₁/c. The ions are linked by N—H⃛O hydrogen bonds [H⃛O = 1.70 and 2.30 Å, N⃛O = 2.624 (2) and 3.136 (2) Å, and N—H⃛O = 178 and 151°], and the ethanol mol­ecule is linked to the anion by an O—H⃛O hydrogen bond [H⃛O = 1.90 Å, O⃛O = 2.728 (2) Å and O—H⃛O = 171°], to form a centrosymmetric five‐component aggregate. C—H⃛O hydrogen bonds and aromatic π–π‐stacking interactions are absent, but the aggregates are linked into sheets by a single C—H⃛π(arene) hydrogen bond.     

The gas-phase decomposition of methylsilane. Part I. Mechanism of decomposition under shock-tube conditions

The gas-phase decompositions of methylsilane and methylsilane-d₃ have been investigated in a single-pulse shock tube at 4700 torr total pressure in the temperature range of 1125–1250 K. For CH₃SiD₃ at 1200 K three primary steps occur in the homogeneous decomposition with efficiencies in parentheses: , , and . For CH₃SiH₃ at 1200 K the primary CH₄ elimination efficiency is 0.09 while the total primary H₂ elimination efficiency is 0.91. Minor product formations of C₂H₄, acetylene, dimethylsilane, and SiH₄ are discussed.     

Fréchet Means for Distributions of Persistence Diagrams

Given a distribution \(\rho \) on persistence diagrams and observations \(X_{1},\ldots ,X_{n} \mathop {\sim }\limits ^{iid} \rho \) we introduce an algorithm in this paper that estimates a Fréchet mean from the set of diagrams \(X_{1},\ldots ,X_{n}\) . If the underlying measure \(\rho \) is a combination of Dirac masses \(\rho = \frac{1}{m} \sum _{i=1}^{m} \delta _{Z_{i}}\) then we prove the algorithm converges to a local minimum and a law of large numbers result for a Fréchet mean computed by the algorithm given observations drawn iid from \(\rho \) . We illustrate the convergence of an empirical mean computed by the algorithm to a population mean by simulations from Gaussian random fields.     

One‐Step Microfluidic Coating of Phospholipid Microbubbles with Natural Alginate Polymer as a Delivery System for Human Epithelial Lung Adenocarcinoma

In this study, the neoplastic drug frequently used in the treatment of lung cancer, carboplatin is loaded to microbubbles via a microfluidic platform. In order to increase the drug loading capacity of microbubbles, carboplatin is encapsulated into alginate polymer layer. The phospholipid microbubbles (MBs) are synthesized by MicroSphere Creator, which is connected with T‐junction and micromixer for the treatment with CaCl₂ solution to provide gelation of the alginate coated phospholipid microbubbles (AMBs). The carboplatin loaded alginate coated phospholipid microbubbles (CAMBs) result in 12.2 ± 0.21 µm mean size, obtained by mixing with 0.05% CaCl₂ using T‐junction. The cytotoxic activities of the synthesized MBs, AMBs, and CAMBs are also investigated with the 3‐(4,5‐Dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide) (MTT) and live/dead fluorescent dying assays in the A549 and BEAS‐2B cell lines. The one‐step microfluidic coating of lipid microbubbles with natural alginate polymer appears to be a promising strategy for enhanced drug reservoir properties.     

Molecular modeling based approach to potent P2-P4 macrocyclic inhibitors of hepatitis C NS3/4A protease

Molecular modeling of inhibitor bound full length HCV NS3/4A protease structures proved to be a valuable tool in the design of a new series of potent NS3 protease inhibitors. Optimization of initial compounds provided 25a. The in vitro activity and selectivity as well as the rat pharmacokinetic profile of 25a compare favorably with the data for other NS3/4A protease inhibitors currently in clinical development for the treatment of HCV.     

Counterexamples to the well-posedness of transmission boundary value problems for the Laplacian

In this note we show that the well-posedness range for transmission boundary value problems for the Laplacian in the class of Lipschitz domains established by Escauriaza and Mitrea (2004) is sharp. Our approach relies on Mellin transform techniques for singular integrals naturally associated with the transmission problems and on a careful analysis of the spectra of such singular integrals.

     

Utilizing DART mass spectrometry to pinpoint halogenated metabolites from a marine invertebrate-derived fungus

Prenylated indole alkaloids are a diverse group of fungal secondary metabolites and represent an important biosynthetic class. In this study we have identified new halogenated prenyl-indole alkaloids from an invertebrate-derived Malbranchea graminicola strain. Using direct analysis in real time (DART) mass spectrometry, these compounds were initially detected from hyphae of the fungus grown on agar plates, without the need for any organic extraction. Subsequently, the metabolites were isolated from liquid culture in artificial seawater. The structures of two novel chlorinated metabolites, named (-)-spiromalbramide and (+)-isomalbrancheamide B, provide additional insights into the assembly of the malbrancheamide compound family. Remarkably, two new brominated analogues, (+)-malbrancheamide C and (+)-isomalbrancheamide C, were produced by enriching the growth medium with bromine salts.     

Why is chemical synthesis and property optimization easier than expected?

Identifying optimal conditions for chemical and material synthesis as well as optimizing the properties of the products is often much easier than simple reasoning would predict. The potential search space is infinite in principle and enormous in practice, yet optimal molecules, materials, and synthesis conditions for many objectives can often be found by performing a reasonable number of distinct experiments. Considering the goal of chemical synthesis or property identification as optimal control problems provides insight into this good fortune. Both of these goals may be described by a fitness function J that depends on a suitable set of variables (e.g., reactant concentrations, components of a material, processing conditions, etc.). The relationship between J and the variables specifies the fitness landscape for the target objective. Upon making simple physical assumptions, this work demonstrates that the fitness landscape for chemical optimization contains no local sub-optimal maxima that may hinder attainment of the absolute best value of J. This feature provides a basis to explain the many reported efficient optimizations of synthesis conditions and molecular or material properties. We refer to this development as OptiChem theory. The predicted characteristics of chemical fitness landscapes are assessed through a broad examination of the recent literature, which shows ample evidence of trap-free landscapes for many objectives. The fundamental and practical implications of OptiChem theory for chemistry are discussed.     

Vinyldisiloxanes: their synthesis, cross coupling and applications

During the studies towards the development of pentafluorophenyldimethylsilanes as a novel organosilicon cross coupling reagent it was revealed that the active silanolate and the corresponding disiloxane formed rapidly under basic conditions. The discovery that disiloxanes are in equilibrium with the silanolate led to the use of disiloxanes as cross coupling partners under fluoride free conditions. Our previous report focused on the synthesis and base induced cross coupling of aryl substituted vinyldisiloxanes with aryl halides; good yields and selectivities were achieved. As a continuation of our research, studies into the factors which influence the successful outcome of the cross coupling reaction with both alkyl and aryl substituted vinyldisiloxanes were examined and a proposed mechanism discussed. Further investigation into expanding the breadth and diversity of substituted vinyldisiloxanes in cross coupling was explored and applied to the synthesis of unsymmetrical trans-stilbenes and cyclic structures containing the trans-alkene architecture.