Molecular imine cages with π-basic Au3(pyrazolate) faces

One tetrahedral and two trigonal prismatic cages with π-basic Au3(pyrazolate)3 faces were obtained by connection of pre-formed gold complexes via dynamic covalent imine chemistry. The parallel arrangement of the Au3(pyrazolate)3 complexes in the prismatic cages augments the interaction with π-acids, as demonstrated by the encapsulation of polyhalogenated aromatic compounds. The tetrahedral cage was found to act as a potent receptor for fullerenes. The structures of the three cages, as well as the structures of adducts with C60 and C70, could be established by X-ray crystallography.

Synthesis, Characterization, and Encapsulation Properties of Rigid and Flexible Porphyrin Cages Assembled from N-Heterocyclic Carbene-Metal Bonds

Four porphyrins equipped with imidazolium rings on the para positions of their meso aryl groups were prepared and used as tetrakis(N-heterocyclic carbene) (NHC) precursors for the synthesis of porphyrin cages assembled from eight NHC-M bonds (M = Ag⁺ or Au⁺). The conformation of the obtained porphyrin cages in solution and their encapsulation properties strongly depend on the structure of the spacer -(CH₂)_n- (n = 0 or 1) between meso aryl groups and peripheral NHC ligands. In the absence of methylene groups (n = 0), porphyrin cages are rather rigid and the short porphyrin-porphyrin distance prevents the encapsulation of guest molecules like 1,4-diazabicyclo[2.2.2]octane (DABCO). By contrast, the presence of methylene functions (n = 1) between meso aryl groups and peripheral NHCs offers additional flexibility to the system, allowing the inner space between the two porphyrins to expand enough to encapsulate guest molecules like water molecules or DABCO. The peripheral NHC-wingtip groups also play a significant role in the encapsulation properties of the porphyrin cages.

Self-assembly of chiral BINOL cages via imine condensation

Condensation of an (S)- or (R)-BINOL-derived dialdehyde and tris(2-aminoethyl)amine produced chiral [2+3] imine cages, which were further reduced to furnish more stable chiral amine cages and applied in the enantioselective recognition of (1R,2R)- and (1S,2S)-1,2-diaminocyclohexane.

Reticular Chemistry in the Construction of Porous Organic Cages

Reticular chemistry offers the possibility of systematic design of porous materials with different pores by varying the building blocks, while the emerging porous organic cage (POC) system remains generally unexplored. A series of new POCs with dimeric cages with odd-even behaviors, unprecedented trimeric triangular prisms, and the largest recorded hexameric octahedra have been prepared. These POCs are all constructed from the same tetratopic tetraformylresorcin[4]arene cavitand by simply varying the diamine ligands through Schiff-base reactions and are fully characterized by X-ray crystallography, gas sorption measurements, NMR spectroscopy, and mass spectrometry. The odd-even effects in the POC conformation changes of the [2 + 4] dimeric cages have been confirmed by density functional theory calculations, which are the first examples of odd-even effects reported in the cavitand-based cage system. Moreover, the "V" shape phenylenediamine linkers are responsible for the novel [3 + 6] triangular prisms. The window size and environment can be easily functionalized by different groups, providing a promising platform for the construction of multivariate POCs. Use of linear phenylenediamines led to record-breakingly large [6 + 12] truncated octahedral cages, the maximum inner cavity diameters and volumes of which could be readily modulated by increasing the spacer length of the phenylenediamine linkers. This work can lead to an understanding of the self-assembly behaviors of POCs and also sheds light on the rational design of POC materials for practical applications.

Networked Cages for Enhanced CO2 Capture and Sensing

It remains a great challenge to design and synthesize a porous material for CO2 capture and sensing simultaneously. Herein, strategy of "cage to frameworks" is demonstrated to synthesize fluorescent porous organic polymer (pTOC) by using tetraphenylethylene-based oxacalixarene cage (TOC) as the monomer. The networked cages (pTOC) have improved porous properties, including Brunauer-Emmett-Teller surface area and CO2 capture compared with its monomer TOC, because the polymerization overcomes the window-to-arene packing modes of cages and turns on their pores. Moreover, pTOC displays prominent reversible fluorescence enhancement in the presence of CO2 in different dispersion systems and fluorescence recovery for CO2 release in the presence of NH3·H2O, and is thus very effective to detect and quantify the fractions of CO2 in a gaseous mixtures.

Synthesis and Structural Characterization of a Cyclen-Derived Molecular Cage

Reaction of a tetrafunctionalized cyclen derivative containing four aldehyde groups with an appropriate diamine followed by reduction and demetalation highly efficiently affords a bis(cyclen)-derived molecular cage. Potentiometric investigations show that this compound forms dimetallic complexes with copper(II), with the two metal ions selectively coordinated to the cyclen units. X-ray crystallography indicates that these complexes could give rise to new cascade complexes after incorporation of anions between the metal centers.

Control of the cavity size of flexible covalent cages by silver coordination to the peripheral binding sites

The synthesis of covalent cages consisting of two porphyrins connected by four flexible spacers each incorporating two 1,2,3-triazolyl ligands is reported. Binding of four silver(I) to the peripheral ligands induces conformational changes in solution and locks the porphyrins in a face-to-face disposition.

Crystal Structures of a Molecule Designed Not To Pack Tightly

Organic molecules of intrinsic microporosity (OMIMs) are structurally constructed to not pack tightly. Consequently, only weak interactions between OMIM molecules can occur, which is the reason that almost all OMIMs have been described and investigated in their amorphous states. For the same reason it is very difficult to grow single crystals of OMIMs for X-ray structural analysis. Here we describe four different polymorphs of an OMIM that was before only described in the amorphous state.

Targeted synthesis of a large triazine-based [4+6] organic molecular cage: structure, porosity and gas separation

A novel electron-deficient triazine-based [4+6] organic molecular cage has been synthesized via imine condensation reaction.