Directing group strategies in rhodium-catalyzed C-H amination.

Construction of a carbon-nitrogen bond is one of the most prevalent operations in nature and organic synthesis. The resulting amino compounds are privileged structural fragments in natural products, pharmaceutical drugs, and functional materials. With the rapid advancement of C-H bond activation, directing-group strategies in C-H amination catalyzed by rhodium have emerged. This reaction approach considerably enhances the step economy and atom economy of the reaction, and it complies with green chemistry and atom economy. The reactivity and selectivity of chelation-assisted rhodium-catalyzed C-H amination are discussed in relation to the types of aminating reagent, as well as the challenges and future development prospects in this field.

Single-Molecule-Magnet Behavior in a [2 × 2] Grid Dy(III)4 Cluster and a Dysprosium-Doped Y(III)4 Cluster.

Thanks to the MeCN hydrolysis in situ reaction, a [2 × 2] square grid Dy(III)4 cluster based on a polypyridyl triazolate ligand, [Dy4(OH)2(bpt)4(NO3)4(OAc)2] (1), was separated successfully and characterized through single-crystal X-ray diffraction and SQUID magnetometry. The frequency-dependent signals in the out-of-phase component of the susceptibility associated with slow relaxation of the magnetization confirmed that complex 1 displays single-molecule magnet (SMM) behavior. Two distinct slow magnetic relaxation processes, with effective energy barriers Ueff1 = 93 cm(-1) for fast relaxation and Ueff2 = 143 cm(-1) for slow relaxation observed under a zero direct-current field, are mainly attributed to the origin of single-ion behavior, which can be further acknowledged by the magnetic investigation of a dysprosium-doped yttrium cluster. Besides, it should be noted that complex 1 represents so far the highest energy barrier among the pure Dy(III)4 SMMs.

The first {Dy4} single-molecule magnet with a toroidal magnetic moment in the ground state.

A toroidal magnetic moment in the absence of a conventional total magnetic moment was first observed in a novel tetranuclear dysprosium cluster with nonmagnetic ground state. The toroidal state is quite robust with respect to variations of the exchange parameters.