Intermolecular spin–spin coupling constants between P atoms

This paper reports the study by NMR spectroscopy and ab initio methods of the structure of 3,4-dimethyl-1-cyanophosphole and its dimer. The dimer presents a P···P interaction of the pnictogen type due to the presence of σ-holes. NMR of the monomer was recorded in CDCl₃ solution while NMR of the dimer corresponds to the solid state (CPMAS) experiments. The ^2pJ_PP spin–spin coupling constant has not been measured, but calculated at the B3LYP level. AIM, NBO and ELF methodologies have been used to describe the electronic structure of the dimer.     

Filler effects on the thermomechanical response of stretched rubbers

This paper deals with the calorimetric analysis of deformation processes in filled styrene-butadiene rubbers. More especially, the study focuses on the effects of the addition of carbon black fillers on the calorimetric response of “demullinized” SBR. Temperature variations are measured by infrared thermography during cyclic uniaxial tensile tests at ambient temperature. Heat sources¹ produced or absorbed by the material due to deformation processes are deduced from temperature fields by using the heat diffusion equation. First, the results show that no mechanical (intrinsic) dissipation is detected for weakly filled SBR, meaning that the heat produced and absorbed over one mechanical cycle is the same whatever the stretch ratio reached. Second, the mechanical dissipation in highly filled SBR is significant. The quantitative analysis carried out highlights the fact that it increases quasi-linearly with the stretch ratio. Finally, a simplified framework is proposed to discuss the identification of the heat sources, in particular the mechanical dissipation.     

Magnetic field induced Freedericksz transition of a planar aligned liquid crystal doped with metalloporphyrins FeTPPCl,MnTPPCl and ZnTPP

We observed that the planar aligned nematic liquid crystal (5CB) doped with a volume fraction of 1% of FeTPPCl [5,10,15,20-tetraphenylporphyriniron(III)chloride] or MnTPPCl [5,10,15,20-tetraphenylporphyrinmanganese(III)chloride] dramatically decreased the critical magnetic field for the magnetic field induced Freedericksz transition, while 5CB doped with ZnTPP [5,10,15,20-tetraphenylporphyrinzinc(II)] revealed no such effect, when compared with pure 5CB. In the guest-host (5CB) system, FeTPPCl and MnTPPCl as guests are both strong paramagnetic materials with an interaction through coordination of the -CN group in 5CB onto the metal ion of the porphyrin. As a result, the 5CB molecules are dragged to reorientate under a static magnetic field, while ZnTPP is a diamagnetic material without such a property. This phenomenon concerning magneto-optical components could be useful in liquid crystal displays.     

Conformational Analysis of the Anti‐obesity Drug Lorcaserin in Water: How To Take Advantage of Long‐Range Residual Dipolar Couplings

The conformational state of 8‐chloro‐1‐methyl‐2,3,4,5‐tetrahydro‐1H‐3‐benzazepine hydrochloride (lorcaserin) in water has been determined on the basis of one‐bond and long‐range C? H residual dipolar coupling (RDC) data along with DFT computations and ³J_HH coupling‐constant analysis. According to this analysis, lorcaserin exists as a conformational equilibrium of two crown‐chair forms, of which the preferred conformation has the methyl group in an equatorial orientation.     

Synthesis and characterization of hydrophilic theophylline base compounds and their use as ligands in the microwave assisted Suzuki–Miyaura couplings of halopyridines in water

Xanthine derivatives, caffeine (L1), theobromine (L2), theophylline (L3), 7-(β-hydroxyethyltheophylline) (L4), (7-(2,3-dihydroxypropyl)theophylline) (L5), and theophylline 7-acetic acid (L6) and the acetylated derivatives of the later three (L7–L9) were employed as ligands for the in situ palladium catalyzed Suzuki–Miyaura cross couplings of a series of halogenated pyridines. Optimized conditions were found where the diacetylated ligand (L8) was determined to be the best for this process, producing good to excellent yields in the couplings of halogenated anilines with phenylboronic acid under mild reaction conditions in water using microwave irradiation.     

Utilization of photocatalysts in decarboxylative coupling of carboxylic N-hydroxyphthalimide (NHPI) esters

Recently, the visible-light photoredox decarboxylative couplings of N-(acyloxy)phthalimides (NHPI esters) and its derivatives have become an efficient chemical transformation. Under visible light, the NHPI esters undergo a single-electron transfer (SET) process to afford the corresponding carbon or nitrogen radicals that participate in many chemical transformations. The photoredox decarboxylative couplings have been applied to achieve construction of an array of carbon–carbon and carbon–heteroatom bonds as well as the synthesis of carbocycles and heterocycles. This review categorises photocatalysts, discusses the application and catalysis mechanisms of NHPI esters, and details recent progress in this field.     

Non-linear couplings,from the early to the late time universe

Deciphering the mechanisms at play in the formation and evolution of the large-scale structure of the universe is part of the scientific goals of many projects of observational cosmology. In particular, large-scale structure observations can be used to infer mode-coupling effects, whether they come from the physics of the early universe or from its late time evolution. Specificities of such couplings are presented, noting that in principle they can be directly detected through bispectra of the cosmic microwave background temperature anisotropies or density in the local universe. The existence of such couplings have however more far-reaching consequences for the growth of the structure. Those are sketched as well as their possible observational impacts.     

Metal‐Catalyzed Reductive Coupling Reactions of Organic Halides with Carbonyl‐Type Compounds

Metal‐catalyzed reductive coupling reactions of aryl halides and (pseudo)halides with carbonyl‐type compounds have undergone an impressive development within the last years. These methodologies have shown to be a powerful alternate strategy, practicality aside, to the use of stoichiometric, well‐defined, and, in some cases, air‐sensitive organometallic species. In this Minireview, the recent findings in this field are summarized, with particular emphasis on the mechanistic interpretation of the results and future aspects of this area of expertise.     

第一过渡系金属-镝单分子磁体研究进展与展望

第一过渡系中的顺磁性离子Cr^Ⅲ、Mn^Ⅱ/Mn^Ⅲ、Fe^Ⅱ/Fe^Ⅲ、Co^Ⅱ、Ni^Ⅱ和Cu^Ⅱ及抗磁性离子Co^Ⅲ和Zn^Ⅱ均可与Dy^Ⅲ在多齿螯合配体配位下形成单分子磁体配合物。在本文中,我们阐述或汇总了几乎所有的第一过渡系金属-镝单分子磁体。对于由顺磁性第一过渡金属离子和Dy^Ⅲ离子形成的配合物,有2个有趣的现象需要引起人们的注意：一是一些Cr-Dy配合物具有较高的阻塞温度和较大的矫顽场,这可归功于配合物内Cr^Ⅲ离子和Dy^Ⅲ离子之间较强的磁耦合作用（|J|>10 cm^-1）。二是报道的Fe^Ⅱ₂-Dy配合物的能垒可达到319 cm^-1（459 K）,这在第一过渡系金属-镝单分子磁体中也是比较高的。这可能与Fe^Ⅱ₂-Dy中Dy^Ⅲ具有较高的轴向对称性（D_5h）有关,且从头计算表明该配合物中Dy的第一激发态也具有较高的轴向对称性。除了部分Cr-Dy和Fe^Ⅱ-Dy配合物外,其他顺磁性第一过渡金属-Dy的能垒较低,这可能由配合物内顺磁离子间弱的磁耦合造成的。为了消除磁耦合对磁弛豫行为影响,近年来人们关注于使用抗磁性第一过渡金属离子与Dy^Ⅲ构建单分子磁体配合物。相比其他核数的Zn-Dy配合物,三核Zn₂Dy配合物被报道的数目最多且研究得最为深入,这可能与较易调控Zn₂Dy中Dy配位几何对称性有关。最后,我们提出了几点关于进一步提升第一过渡系金属-镝单分子磁体的磁性能的建议,其中最为重要的是控制Dy配位几何的轴向对称性及Dy的基态m_J的电荷分布。对于第一过渡系金属-镝单分子磁体中的Dy^Ⅲ离子,Dy^Ⅲ基态m_J的电荷与配体的电荷之间的静电排斥应该降到最低。