The interaction of two-level atoms with a single-mode light field is an extensively studied many-body problem in quantum optics, first analyzed by Dicke in the context of superradiance. A characteristic of such systems is the cooperative enhancement of the coupling strength by a factor of N. In this study, we extended this cooperatively enhanced coupling to a solid-state system, demonstrating that it also occurs in a magnetic solid in the form of matter-matter interaction. Specifically, the exchange interaction of paramagnetic erbium(III) (Er) spins with an iron(III) (Fe) magnon field in erbium orthoferrite (ErFeO) exhibits a vacuum Rabi splitting whose magnitude is proportional to N. Our results provide a route for understanding, controlling, and predicting novel phases of condensed matter using concepts and tools available in quantum optics.

The cleavage and functionalization of CÀH bonds is of fundamental interest for both academia and industry. Generally, the transformation relies on transition metals, [1] which are involved in four major approaches: 1) electrophilic activation of the C À H bond by a high-valent transition metal; 2) oxidative addition to the C À H bond by low-valent transition metals; 3) C À H bond activation by s-bond metathesis, and 4) insertion of a metal carbenoid/nitrenoid into the CÀ H bond. After extensive studies, transition-metal-catalyzed CÀH activation has arisen as an excellent synthetic method to build complex structures because it reduces prefunctionalization while improving atom economy and energy efficiency. However, the use of expensive metal catalysts and the problems involved in removing the residual metals from the final products, which is usually a difficult and tedious process, limits the practical applications of this strategy. The discovery of an efficient CÀH transformation that does not require a metal catalyst would be of great value. This strategy would eliminate the requirement to remove traces of metal from the final products and solve the problem of disposal of the metal catalyst from the reaction mixtures. Recently, several groups disclosed a variety of novel C À C bond formations by using CÀH activation under transition-metalfree conditions. [2,3] The cross-dehydrogenative coupling (CDC) reaction, beyond traditional cross-couplings, has been the object of increasing interest over the last ten years. However, transition-metal catalysts, such as iron and copper salts, were usually required to promote this transformation. [4,5]

All reported attempts to synthesize the tert-butyl-substituted adamantoid phosph(III)azane P4 (N(t) Bu)6 have failed, leading to the classification of this molecule as inaccessible and a literature example of steric control in chemistry of phosphorus-nitrogen compounds. We now demonstrate that this structure is readily accessible by a solvent-free mechanochemical milling approach, highlighting the importance of mechanochemical reaction environments in evaluating chemical reactivity.

A general alkylation of heterocycles using a simple palladium catalyst is reported. Most classes of heterocycles, including indoles and pyridines, efficiently coupled with unactivated secondary and tertiary alkyl halides. An alkyl radical addition to neutral heteroarenes is most likely involved.

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The particle swarm optimization method in conjunction with density functional calculations is used to search the lower energy structures for the cationic water clusters (H2O)5(+). Geometry optimization, vibrational analysis, and infrared spectrum calculation are performed for the most interesting clusters at the MP2/aug-cc-pVDZ level. The relationships between their structural arrangements and their energies are discussed. According to their relative Gibbs free energies, their energy order is determined and four lowest energy isomers are found to have a relative population surpassing 1% below 350 K. Studies reveal that, among these four isomers, one new cluster found here also contributes a lot to the experimental infrared spectrum. Based on topological analysis and reduced density gradient analysis, some meaningful points are found by studying the structural characteristics and the bonding strengths of these cationic water clusters: in the first solvation shell, the central H3O(+) motifs may have a stronger interaction with the OH radical than with the water molecules. The interaction in the second solvation shell may also be stronger than that in the first solvation shell, which is opposite to our intuition.

A simple protocol for hydrodebromination and -deiodination of halo(hetero)arenes was enabled by sodium hydride (NaH) in the presence of lithium iodide (LiI). Mechanistic studies showed that an unusual concerted nucleophilic aromatic substitution operates in the present process.

We report here a Cu-catalyzed enantioselective acyloxylation of cyclic diaryliodonium salts. With readily available cyclic diaryliodonium salts and ubiquitous aliphatic or (hetero)­aromatic carboxylic acids as the starting materials, various axially chiral acyloxylated 2-iodobiaryls were prepared in excellent yield and with excellent enantioselectivity (mostly 99% yield and 99% ee). Density functional theory calculations were conducted to reveal the stereo- and regioselectivities. This simple reaction protocol can be employed for the late-stage modification of some drug molecules. Finally, by diversity-oriented transformations, these acyloxylated 2-iodobiaryl products can be easily transformed into diverse valuable functionalized biaryls that could be used as chiral ligands or functional materials.