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We have combined single crystal neutron and x-ray diffractions to investigate the magnetic and crystal structures of the honeycomb lattice Na2IrO3. The system orders magnetically below 18.1(2) K with Ir 4+ ions forming zigzag spin chains within the layered honeycomb network with an ordered moment of 0.22(1) µB/Ir site. Such a configuration sharply contrasts with the Néel or stripe states proposed in the Kitaev-Heisenberg model. The structure refinement reveals that the Ir atoms form a nearly ideal two-dimensional honeycomb lattice while the IrO6 octahedra experience a trigonal distortion that is critical to the ground state. The results of this study provide much needed experimental insights into the magnetic and crystal structure that are crucial to the understanding of the exotic magnetic order and possible topological characteristics in the 5d-electron-based honeycomb lattice.

The application of metal-organic frameworks (MOFs) to anion separations with a special emphasis on anion selectivity is reviewed. The coordination frameworks are classified on the basis of the main interactions to the included anion, from weak and non-specific van der Waals forces to more specific interactions such as coordination to Lewis acid metal centers or hydrogen bonding. The importance of anion solvation phenomena to the observed anion selectivities is highlighted, and strategies for reversing the Hofmeister bias that favors large, less hydrophilic anions, and for obtaining peak

The development of ion-pair receptors, with the goal of achieving a higher level of control over recognition than that obtainable from simple ion binding, has intrigued researchers in supramolecular chemistry over the past decade.[1] Many reports have appeared during this period that describe the synthesis and study of very sophisticated receptor designs incorporating a range of electron-pair donor and acceptor groups. Most, if not all, of this work has been performed in the context of creating so-called ion-pair or salt hosts that will bind cation-anion pairs in homogeneous solution or enhance their extraction or transport under interfacial conditions. Whether the ditopic architecture in such systems confers real advantages over simpler combinations of single-ion receptors remains an open question. However, the utility of ion-pair

The utilization of N,N'-disubstituted ureas and thioureas as design elements in the synthesis of crystalline organic solids is reviewed. These hydrogen-bonding units are versatile yet predictable building blocks that can be rationally employed in both crystal assembly and functionalization.