Anionic wheels for cationic axles: Significant electrostatic ion–ion interactions dramatically increase the stability of interpenetrated molecules. In highly polar solvents, formation of [2]pseudorotaxanes is observed, in which crown ether wheels (see picture, red) having anionic sulfonate groups counter the pyridinium cations of the axle (blue).

Three new silver sulfonate metal-organic frameworks are presented along with a design strategy for future generations. [[Ag6(mesitylenetrisulfonate)2(H2O)5].2H2O]infinity (1), [Ag4(durenetetrasulfonate)(H2O)2](infinity) (2), and [[Ag4(1,3,5,7-tetrakis(4,4'-sulfophenyl)adamantane)(H2O)2].1.3H2O]infinity (3) represent a series of open-framework silver sulfonate solids where the organic linker plays a key role in determining the overall structure. Compound 1 forms a pillared layered structure, while compounds 2 and 3 form 3-D nets derived from cross-linking of 1-D columns of silver sulfonates. All three solids incorporate water molecules, which can be removed to yield a solid stable to in excess of 300 degrees C. Powder X-ray diffraction studies and vapor sorption experiments show, for 1 and 2, that the solids retain their structure when guests are removed and, for all three, that water vapor is resorbed stoichiometrically by the solids. An idealized silver sulfonate framework is proposed, and upon comparison to the reported structures, guidelines are proposed for structural constraints in the design of future generations of 1-D and possibly 0-D aggregate structures.

The dynamic nature of mechanically interlocked molecules has been shown to be particularly useful for the construction of molecular machines.[1] A great deal of information about the potential for the fabrication of nanoscale devices from these units has been gleaned from studies of their fundamental properties in solution.[2] The incorporation of these individual molecular components into the repeating framework of crystalline materials provides a simple method for imposing the type of higher order required for future applications. [3] A simple interlocked unit from which various types of molecular machines have been constructed is the [2]rotaxane. We have recently shown that a [2]pseudorotaxane comprising a dipyridinium axle and a dibenzo-[24]crown-8 ether (DB24C8) wheel [4] could be used to construct solid-state materials in the form of coordination polyrotaxanes in which every bridging ligand is a [2]rotaxane.[5] These materials contained varying degrees of porosity as there was no detectable interpenetration of nets [6] even though the metal-metal distances are over 22 . [7] Unfortunately, regardless of the metal to ligand ratio, a two-dimensional (2D) square net was the highest order attainable with this dynamic ligand and d block transition-metal ions. It was rationalized that a three-dimensional (3D) network was simply not possible owing to the crowding occurring on placing six of these sterically demanding ligands around a single metal ion. To circumvent this problem the dipyridinium ligand was extended by forming the bis(N-oxide) analogue, axle 1 2+ . This new axle was prepared from the reaction of 4,4'-bipyridine mono-N-oxide with 1,2-dibromoethane and subsequent anion exchange to triflate utilizing the same conditions used to make the bis(4,4'bipyridinium)ethane axle. [4b, 8]

Anionische Räder für kationische Achsen: Elektrostatische Ion‐Ion‐Wechselwirkungen führen zu beträchtlich stabilen Rotaxankomplexen. In hochpolaren Lösungsmitteln wird die Bildung von [2]Pseudorotaxanen beobachtet, in denen Kronenether‐Räder (siehe Bild, rot) mit anionischen Sulfonatgruppen die Pyridiniumkationen der Achse (blau) ausgleichen.

By employing a rigid adamantane-based unit as a spacer, a coordination solid with an open channel layered structure results showing the first observation of metal sulfonate clusters. The design approach employed enforces a structural mismatch of metal and ligand coordinative preferences.