Total Synthesis of the Diterpenoid (+)‐Harringtonolide

Described herein is the first asymmetric total synthesis of (+)‐harringtonolide, a natural diterpenoid with an unusual tropone imbedded in a cagelike framework. The key transformations include an intramolecular Diels–Alder reaction and a rhodium‐complex‐catalyzed intramolecular [3+2] cycloaddition to install the tetracyclic core as well as a highly efficient tropone formation.     

Effect of Ce on resistivity of Sn-3.8Ag-0.7Cu-xCe lead-free solders

The electrical resistivity of Sn-3.8Ag-0.7Cu-xCe (x takes 0, 0.2, 0.5 and 1.0 weight per cent) alloy as a function of temperature was measured by DC four-probe technique. Abnormal changes occurred on the resistivity–temperature (ρ–T) curves above the liquidus, which suggested that the temperature-induced liquid–liquid structure transition probably occurred in Sn-3.8Ag-0.7Cu-xCe melt, with some reversible characters. With the increasing of Ce, the melting range was expanded from 13.0°C to 24.2°C, and the resistivity increased sharply when the Ce composition increased to 0.2%, and then declined slightly. In addition, the temperature and behaviour of abnormal zone were affected by the different additions of Ce.     

Geometric phase of an accelerated two-level atom in the presence of a perfectly reflecting plane boundary

We study the geometric phase of a uniformly accelerated two-level atom coupled with vacuum fluctuations of electromagnetic fields in the presence of a perfectly reflecting plane. We find that the geometric phase difference between the accelerated and inertial atoms which can be observed by atom interferometry crucially depends on the polarizability of the atom and the distance to the boundary and it can be dramatically manipulated with anisotropically polarizable atoms. In particular, extremely close to the boundary, the phase difference can be increased by two times as compared to the case without any boundary. So, the detectability of the effects associated with acceleration using an atom interferometer can be significantly increased by the presence of a boundary using atoms with anisotropic polarizability.     

A Multifunctional Nanocrystalline CaF2:Tm,Yb@mSiO2 System for Dual‐Triggered and Optically Monitored Doxorubicin Delivery

Daunting challenges in investigating the controlled release of drugs in complicated intracellular microenvironments demand the development of stimuli‐responsive drug delivery systems. Here, a nanoparticle system, CaF₂:Tm,Yb@mSiO₂, made of a mesoporous silica (mSiO₂) nanosphere with CaF₂:Tm,Yb upconversion nanoparticles (UCNPs) is developed, filling its mesopores and with its surface‐modified with polyacrylic acid for binding the anticancer drug molecules (doxorubicin, DOX). The unique design of CaF₂:Tm,Yb@mSiO₂ enables us to trigger the drug release by two mechanisms. One is the pH‐triggered mechanism, where drug molecules are preferentially released from the nanoparticles at acidic conditions unique for the intracellular environment of cancer cells compared to normal cells. Another is the 808 nm near infrared (NIR)‐triggered mechanism, where 808 nm NIR induces the heating of the nanoparticles to weaken the electrostatic interaction between drug molecules and nanoparticles. In addition, luminescence resonance energy transfer occurs from the UCNPs (the energy donor) to the DOX drug (the energy acceptor) in the presence of 980 nm NIR irradiation, allowing us to monitor the drug release by detecting the vanishing blue emission from the UCNPs. This study demonstrates a new multifunctional nanosystem for dual‐triggered and optically monitored drug delivery, which will facilitate the rational design of personalized cancer therapy.     

Syntheses,Structures, and Properties of Mono‐ and Tetranuclear Nickel(II) Complexes Derived from a Tridentate Schiff Base Ligand

Three new nickel(II) complexes constructed with N‐(2‐hydroxybenzyl)‐β‐alanine (H₂L), namely [NiL(phen)H₂O]·H₂O ( 1 ) (phen = 1.10‐phenanthroline), [Ni₄L₄(H₂O)₄]·5H₂O ( 2 ) and K[Ni₄L₄(NCS)(H₂O)₅]·5.42H₂O ( 3 ) have been synthesized and characterized by single‐crystal X‐ray diffraction analysis. Complex 1 exhibits a discrete structure, and the structures are bound together through hydrogen bonding to a one‐dimensional chain in ladder‐like fashion. Complexes 2 and 3 contain similar [Ni₄(μ₂‐O)₆] cores with “zig‐zig” arrangement. In complex 3 , the tetranuclear nickel units [Ni₄L₄(H₂O)₄] and [Ni₄L₄(NCS)(H₂O)] are alternately bridged by potassium atoms to a one‐dimensional chain. The neighboring chains are further linked up by {K₂O₂} units to a two‐dimensional layer structure. Moreover, the IR, XRD, TGA and the temperature‐dependent magnetic susceptibility for 2 and 3 have also been studied.     

Probing the electronic structure and chemical bonding of gold oxides and sulfides in AuOn(-) and AuSn(-) (n = 1, 2)

The Au-O and Au-S interactions are essential in nanogold catalysis and nanotechnology, for which monogold oxide and sulfide clusters serve as the simplest molecular models. We report a combined photoelectron spectroscopy and ab initio study on AuO (-) and AuO 2 (-) and their valent isoelectronic AuS (-) and AuS 2 (-) species to probe their electronic structure and to elucidate the Au-O and Au-S chemical bonding. Vibrationally resolved spectra were obtained at different photon energies, providing a wealth of electronic structure information for each species. Similar spectra were observed for AuO (-) and AuS (-) and for the linear OAuO (-) and SAuS (-) species. A bent isomer was also observed as Au(S 2) (-) in the AuS 2 (-) spectra, whereas a similar Au(O 2) (-) complex was not observed in the case of AuO 2 (-). High-level ab initio calculations were conducted to aid spectral assignments and provide insight into the chemical bonding in the AuX (-) and AuX 2 (-) molecules. Excellent agreement is achieved between the calculated electronic excitations and the observed spectra. Configuration interactions and spin-orbit couplings were shown to be important and were necessary to achieve good agreement between theory and experiment. Strong covalent bonding was found in both the AuX (-) and the XAuX (-) species with multiple bonding characters. While Au(S 2) (-) was found to be a low-lying isomer with a significant binding energy, Au(O 2) (-) was shown to be unbound consistent with the experimental observation. The latter is understood in the context of the size-dependent reactivity of Au n (-) clusters with O 2.     

A photoelectron spectroscopic and theoretical study of B16- and B16(2-): an all-boron naphthalene

The structure and chemical bonding of B16- were studied using ab initio calculations and photoelectron spectroscopy. Its global minimum is found to be a quasi-planar and elongated structure (C2h). Addition of an electron to B16- resulted in a perfectly planar and closed shell B16(2-) (D2h), which is shown to possess 10 pi electrons with a pi-bonding pattern similar to that of naphthalene and can thus be considered as an "all-boron naphthalene", a new member in the growing family of hydrocarbon analogues of boron clusters.     

Solvent fuming dual-responsive switching of both wettability and solid-state luminescence in silole film

A multiresponsive switcher on both wettability and solid-state luminescence has great application potentials in novel smart devices. In this paper, a silole molecule of 1,2,3,4,5-hexaphenylsilole (HPS) was chosen to prepare thin films by spin-coating, and a solvent fuming dual-responsive switcher combining photoluminescent behavior and wettability was successfully achieved by changing the mode of solid-state molecular packing. This study suggests that HPS and other silole derivatives have a promising future for use in dual- and multifunctional switches in new technological applications.     

The synthesis and anions complexation property of novel biscalixarene: dumbbell shaped biscalix[4]-1,3-aza-crown

By reacting calix[4]-1,3-aza-crown 2 with 1,6-diisocyanatohexane in “1+2” condensation mode, the first example dumbbell shaped biscalix[4]-1,3-aza-crown 3 was conveniently prepared in yield of 94%. The complexation properties of compound 3 were investigated by UV–vis spectra and ¹H NMR experiments. The results showed that compound 3 has good complexation abilities for anions. Compound 3 binded monoacidic anions with 1:2 binding-stoichiometry and binded binary acidic anions with 1:1 binding-stoichiometry.     

Preparation and characterization of Pluronic/TPGS mixed micelles for solubilization of camptothecin

To increase the solubility and cytotoxicity of poorly soluble anticancer drug camptothecin (CPT), mixed micelles made of Pluronic P105 (P105) and d-alpha-tocopheryl polyethylene glycol 1,000 succinate (TPGS) were prepared. The interaction of Pluronic and TPGS was studied and critical micelle concentration (CMC) was used to evaluate the micellar stability towards dilution. Poorly soluble anticancer drug CPT was incorporated into the mixed micelles. The solubility of CPT by the mixed micelles was more than that of the free drug. The cytotoxicity of the CPT-loaded mixed micelles against MCF-7 cancer cell in vitro was remarkably higher than that of the free drug.