Synthesis,structure,and host-guest chemistry of a pair of isomeric selenanthrene-bridged molecular cages

A pair of selenanthrene-bridged molecular cages have been constructed through a one-step cyclization reaction of a tetrakis(iodo) crown ether with selenium powder. The tubular belt-shaped cage has an intrinsic cavity which can adaptively transform to accommodate electron-deficient guests forming [2]pseudorotaxane complexes. The other product was determined to be an isomeric cage featuring a Mobius strip structure, which exhibits slower twist-migration dynamics than its thianthrene counterpart. The success of using selenanthrene as joints enables an alternative way to structural design and property regulation of molecular cages.

C–H…S Hydrogen Bond Assisted Supramolecular Encapsulation of Fullerenes with Nanobelts

Hydrogen-bonded capsules have been widely employed as supramolecular hosts for organic molecular guests.Encapsulation of fullerenes by capsules is relatively scarce,especially those that utilize sulfur atoms as hydrogen-bond acceptors.Herein,we describe,in both solution and solid state,a bowl-shaped nanobelt[8]cyclophenoxathiin 1a and its tetra-methylated derivative 1b that can form C–H⋯S hydrogen-bonded capsules induced by complexation with suitable fullerenes.1a strongly encapsulates C60,C70,or 6,6-phenyl-C61-butyric acid methyl ester(PC61BM)to form a 2∶1 ternary complex featuring 16 equatorial(sp2)C–H⋯S hydrogen bonds.A pseudorotaxane structure was further obtained for the complex of 1a with PC61BM.Conversely,a 1∶1 inclusion complex was observed for binding C60 or PC61BM with 1b indicating the reduced tendency to form capsules by introducing methyl groups into the belt.Surprisingly,the capsule-like structure was retained for the 1:2 complex of C70 with 1b as observed by the presence of multiple(sp3)C–H⋯S hydrogen bonds.The strong binding affinity and tailorable complexation mode enable further applications of nanobelts in fullerene chemistry.

Applying reticular synthesis to the design of Cu-based MOFs with mechanically interlocked linkers

The concept of“robust dynamics”describes the incorporation of mechanically interlocked molecules(MIMs)into metal-organic framework(MOF)materials such that large amplitude motions(e.g.,rotation or translation of a macrocycle)can occur inside the free volume pore of the MOF.To aid in the preparation of such materials,reticular synthesis was used herein to design rigid molecular building blocks with predetermined ordered structures starting from the well-known MOF NOTT-101.New linkers were synthesized that have a T-shape,based on a triphenylene tetra-carboxylate strut,and their incorporation into Cu(II)-based MOFs was investigated.The single-crystal structures of three new MOFs,UWCM-12(fof),β-UWCM-13(loz),UWCM-14(lil),with naked T-shaped linkers were determined;β-UWCM-13 is the first reported example of the loz topology.A fourth MOF,UWDM-14(lil)is analogous to UWCM-14(lil)but contains a[2]rotaxane linker.Variable-temperature,^(2)H solid-state NMR was used to probe the dynamics of a 24-membered macrocycle threaded onto the MOF skeleton.