Bidirectional chemo‐switching of magnetism occurs in a microporous coordination polymer containing spin‐crossover subunits, as described by M. Ohba, J. A. Real, S. Kitagawa, and co‐workers in their Communication on page 4767 ff. In situ magnetic measurements reveal that most guest molecules transform the framework spin state from diamagnetic low spin (red) to paramagnetic high spin (yellow), whereas the guest CS2 stabilizes the low‐spin state. These induced spin states are retained as a memory effect after the release of the guest.
How low can you go? An FeII4 square was prepared by self‐assembly and exhibits both thermally induced and photoinduced spin crossover from a system with four high‐spin (HS) centers to one with two high‐spin and two low‐spin (LS) centers. The spin‐crossover sites are located on the same side of the square, and the spin transition and magnetic interactions (see picture) are synergistically coupled.
No legendary Prussian order! The distribution of vacancies in Prussian blue analogues is not random, and the spin density on the Cd2+ ion varies depending on the number of paramagnetic ions in its surroundings. This conclusion follows from 113Cd solid‐state magic‐angle spinning NMR studies of [Cd3{Fe/Co(CN)6}2]?15 H2O, where the presence of small but significant spin density on the observed 113Cd nucleus leads to improved spectral resolution.
To “B” or not to “B” : The unusual bonding of boron in organoboranes or oligoboron clusters is not only apparent in diamagnetic molecules but also in paramagnetic systems, including mixed‐valent species and oligoborane/carborane cluster radicals. The picture shows the singly occupied molecular orbital of the radical ion [C4B8R4H8].?, determined by DFT calculations.
The cover picture shows a new protocol for the NiCl2 ‐catalyzed cross‐electrophile coupling of aryl bromides with pyrimidin‐2‐yl tosylates to give the corresponding C2 ‐arylation pyrimidine derivatives. This study provides an improvement over previous methods by using pyrimidin‐2‐yl tosylates instead of halides as coupling partners that are stable and easily available. More details are discussed in the article by Wang et al. on page 1366–1370.
Stuck on sulfur : The first transition‐metal complexes with S? Br units are surprisingly stable. Solid 3 is stable for at least six months and under vacuum solid 2 does not lose Br2. The formation of the first structurally characterized transition‐metal arenesulfenyl bromide complex 3 occurs with a change of the spin ground state from S=2 to S=0.
Coupling of various substituted phenacyl acetates 1 and diazonium salts 3 was studied. If the phenacyl acetates were substituted by an electronaceptor group such as CN or COOEt 3‐substituted phenyl‐5‐(phenyl‐hydrazono)‐5H‐furan‐2‐ones 4 were formed. Also synthesis of aza and diaza analogs is described. The compounds were characterized using MS and NMR spectroscopy. 相似文献
A light touch is all that is required to cleave a maleimide C? N bond to effect a [5+2] photocycloaddition with a sterically encumbered C?N moiety (see scheme).
The metal-polyyne polymers consisting of transition metals and conjugated tetrayne systems where M represents ? Pt(PBu3)2? or ? Pd(PBu3)2? moiety were prepared by the oxidative coupling method and characterized by spectral analysis, associated with novel depolymerization giving binuclear transition metal complexes, and 相似文献
A happy ending : The germanium(II) hydride [LGeH], where L=[HC{(CMe)(2,6‐iPr2C6H3N)}2], reacts with a diazoalkane to form the hydrazone derivative (see picture). The reaction proceeds through the unprecedented end‐on nitrogen insertion of the diazo compound.
Indoles are not indolent : Various indoles react with arylboronic acids chemodivergently. C? H arylation of free indole and N‐methylindole gives the corresponding C(2)‐arylated indoles A whereas N‐acylated, N‐benzoylated, and N‐Boc‐protected indoles provide the corresponding arylcarboaminoxylated products B with excellent diastereoselectivity in good to excellent yields.
Taking shortcuts : A remarkably short and high‐yielding asymmetric total synthesis of (?)‐oseltamivir takes advantage of organocatalysis and single‐pot domino operations. The target, known as the drug Tamiflu, is prepared efficiently in a short time, and also its derivatives can be synthesized effectively.
Poly(para‐phenylene vinylene) (PPV) and its derivatives are important semiconducting polymers for organic electronics. Herein, an alkene metathesis approach to obtain PPVs is reported. Tri(iso propyl)silyl‐substituted norbornadienes are employed as solubilizing agents. As PPV precursors divinylbenzene is used for acyclic diene metathesis and paracyclophane diene for a ring‐opening metathesis polymerization‐type approach. The resulting polymers are analyzed by gel permeation chromatography (GPC), UV‐vis, fluorescence, and nuclear magnetic resonance (NMR) spectroscopy. All of the polymers show good solubility in common solvents.
Furan ring‐functionalized solid surfaces are achieved by the initiated chemical vapor deposition (iCVD) method, a solvent‐free process to form films under mild conditions. The polymerization of furfuryl methacrylate monomer is initiated by a resistively heated filament wire. The functionality of the furan group in the iCVD film enabled Diels–Alder chemistry with 4‐phenyl‐1,2,3‐triazolin‐3,5‐dione (N‐PTD).
Cluster's last stand : Six chiral reduced Schiff base ligands containing amino acids and seven LaIII ions self‐assemble to form a novel heptameric lanthanum supramolecule with the aid of the CO32? ion (see picture). The cluster exists as a single chiral triple helix. The CO32? ion, which is derived from atmospheric CO2 , adopts a rare μ3‐tridentate bridging mode that links three LaIII ions, thus allowing the cluster to efficiently fix CO2.
Weaving an intricate web : A stereoselective synthesis of (?)‐agelastatin A has been developed, which requires 11 steps from commercially available starting material. The application of a Rh‐catalyzed intramolecular olefin aziridination reaction and the subsequent manipulation of the resulting tricyclic intermediate (see scheme) punctuate this study.
Radical assembly : Halogen bonding has been observed for the first time between an isoindoline nitroxide and an iodoperfluorocarbon (see figure), which cocrystallize to form a discrete 2:1 supramolecular compound in which N? O.???I halogen bonding is the dominant intermolecular interaction. This illustrates the potential use of halogen bonding and isoindoline nitroxide tectons for the assembly of organic spin systems.
Reactivity N? Own : Pyridine N‐oxides can be used for the complete regio‐ and stereoselective synthesis of trans‐substituted piperidines. The sequential addition of Grignard reagents and aldehydes or ketones to pyridine N‐oxides yields a complete regio‐ and stereoselective trans 2,3‐addition reaction in high yields, and the substituted 2,3‐dihydropyridine N‐oxide can be reduced to form 2,3‐trans‐substituted piperidines (see scheme).
Preferred protonation : Does electrospray ionization mass spectrometry produce gas‐phase or liquid‐phase structures? The preferred protonation site in p‐aminobenzoic acid depends upon the medium, and the structure of its conjugate acid varies with the solvent used during spraying.
