Lattice Inclusion Host Research Articles

Synthesis and Structure of the Inclusion Compound COF300‐ALA

Comprehensive SummaryFinding a new multimolecular lattice inclusion host is still challenging. We report the synthesis and the crystal structure of the first example of an inclusion compound COF300‐ALA by using three‐dimensional covalent organic frameworks (3D‐COFs) as the multimolecular host lattice. The guest‐host dynamics upon inclusion and exclusion of the gust molecule are uncovered in a 3D covalent organic framework.This article is protected by copyright. All rights reserved.

Tetraarylbiphenyl as a New Lattice Inclusion Host by Structure Reductionism: Shape and Size Complementarity Based on Torsional Flexibility

3,3′,5,5′-Tetrakis(2,6-dimethyl-4-methoxyphenyl)biphenyl (TB) was designed as a lattice inclusion host based on a structure reductionistic approach. TB binds guests in two different domains based on the premise that the two phenyl rings of the biphenyl core remain coplanar in the solid state. The versatility of TB as a host has been demonstrated by its ability to include different guest molecules in the crystal lattice, as revealed by X-ray crystal structure analyses. One observes preference for guest location in the concave domain with the trough domain compromised. The host TB is found to exploit torsional freedom about the central σ-bond between the two phenyl rings of the biphenyl core to adopt discrete structures that are complementary in terms of shape and size to include a given guest. In other words, TB behaves like a “molecular chameleon” that undergoes structural adaptation in response to the guest via torsional twist about the central σ-bond. Quite remarkably, the inclusion compounds with different guests having similar torsional angles between the phenyl rings of the biphenyl core are found to be isostructural. The torsion-induced structural morphosis in response to the guest is found to completely offset binding in the trough region.

Effect of Adding Bromine Sensors to the Central Linker of New Diquinoline Derivative

Designing a selective lattice inclusion host had been challenging and fulfilling. Using 3 as a building block, we introduced bromine sensors to the central linker and investigate its effect on inclusion properties. An unexpected result was obtained when a pure sample of the diquinoline derivative 4 was crystallised from tetrahydrofuran. Unlike host 3, the diquinoline 4 did not include any guest molecules.

Guest Control in the Self-Assembly of H-Shaped Host to Cyclopentanoid (5,43) Net

The H-shaped molecule 1,4-di[bis(4′-hydroxyphenyl)methyl]benzene (1a) and its octamethyl derivative (1b) crystallize in solvated and guest-free forms. CH3NO2 and CHCl3 solvents afforded the rare (5,43) net of contiguous pentagons in a two-dimensional (2D) sheet for 1a and 1b, respectively. The tetrahedral carbon centers are 3-connected nodes and hydrogen bonding OH groups are 4-center nodes of congruent cyclopentanoid rings. The first examples of pentagon layer tiling in a lattice inclusion host are reported.

Synthesis and inclusion properties of new nitrated C2− symmetric diquinoline hosts

The non-host 6,7,14,15-tetrahydro-6,14-methanocycloocta[1,2-b : 5,6-b′]diquinoline3 was nitrated to yield its C2− symmetric dinitro analogues 6 and 7. Both derivatives acted as lattice inclusion hosts in accord with our molecular design. The four X-ray crystal structures reported proved to be very different from each other and are analysed and compared. Although the nitro group does participate in weak intermolecular associations, its major function is shown to be a spoiler group that disrupts simple packing and thereby encourages guest inclusion.

Structural and thermochemical studies of lattice inclusion hosts

Structural and thermochemical studies of lattice inclusion hosts

Why a hexabromodiquinoline host preferentially includes small aromatic hydrocarbon guests.

The preparation and properties of the new hexabromodiquinoline derivative 4 are described. This lattice inclusion host shows a strong preference for trapping small aromatic hydrocarbons. The X-ray crystal structures of the benzene, toluene, o-xylene, and p-xylene compounds are reported, and are analysed from a crystal engineering perspective. Crystallisation of 4 from the dual-nature solvent trifluoromethylbenzene yields the solvent-free material. Comparison of the parent crystal structure with those of its inclusion compounds reveals why inclusion of aromatic hydrocarbon guests is such a favoured process. The high concentration of Br...Br interactions in the structure of pure 4 is diluted and increasingly replaced by aromatic offset face-face (OFF) and aromatic edge-face (EF) interactions in the inclusion compounds, and this results in better lattice packing energies. For toluene, o-xylene, and p-xylene the host-guest ratio is 1:1. Inclusion of the smaller benzene molecule results in a change to 2:3 stoichiometry. This increase in guest content is assisted by replacement of host-host OFF and EF motifs with host-host pi-halogen dimer (PHD) interactions, which provide space for inclusion of the additional guest molecules. These changes result in the most efficient lattice packing of the series for compound (4)2.(benzene)3.

An oxa-bridged tetrahalo aryl lattice inclusion host

The oxygen-substituted diquinoline tetrabromide 11 has been synthesised and found to be a further example of the tetrahalo aryl inclusion host family. This host forms achiral molecular staircases by means of aromatic offset face–face (OFF) and centrosymmetric pi–halogen dimer (PHD) interactions. The X-ray crystal structures of the compounds (11)2·(chloroform) and (11)2·(dichloromethane) show that the included guest molecules occupy channels between the parallel staircases, and that host inter-staircase O⋯Br association is also significant.

Crystal Engineering Involving C−H···N Weak Hydrogen Bonds: Penannular Enclosure of Organic Guests by a Diquinoline Host

The preparation and properties of the racemic lattice inclusion host 6α,13α-dibromo-5bα,6,12bα,13-tetrahydropentaleno[1,2-b:4,5-b′]diquinoline (8) are described. Strong hydrogen bonding interactions are not possible for this versatile host compound. Instead, weaker interactions (such as aryl offset face-face, aryl edge-face, halogen-halogen, halogen-π, and C−H···N synthons) compete against each other to generate the inclusion structure of lowest energy. The guests are contained within molecular pens formed by two hosts enclosing each guest. These host molecules are not directly linked at the corners of the pen, but rather assemble with their neighbours into layers of pens by means of aryl offset face-face interactions. The C−H···N weak hydrogen bond plays a dominant role in these structures by linking adjacent layers edge-edge through two distinct types of double motifs. One is the previously recognised aryl C−H···N dimer, while the other is a new bifurcated Ar−H···N···H−CBr−Ar interaction. The X-ray structures of nine inclusion compounds formed by 8 are reported. Seven of these in space group P21/c have isostructural host lattices where the layers of pens are stacked to produce guest channels. Several different guest arrangements are observed. In contrast, (8)2·(CH3CCl3) in space group C2/c and (8)2·(CF3C6H5) in P212121 have the pen layers stacked so as to enclose their guests in cages. The structure of the nonbrominated precursor 7, which undergoes self-resolution on crystallisation, is also described in crystal engineering terms. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Inclusion Properties of a Chlorinated Diquinoline Host

The new lattice inclusion host 6α,13α-dibromo-2,9-dichloro-5bα,6,12bα,13-tetrahydropentaleno[1,2- b:4,5- b′]diquinoline 8 was prepared, and found to include far fewer guests than its non-chlorinated analogue 2. Compounds ( 8) 2·(ethyl acetate) and ( 8) 2·(benzene) form molecular pen and staircase inclusion compounds respectively. Their X-ray structures are analysed and compared in crystal engineering terms.

Crystal engineering of hydroxy group hydrogen bonding: design and synthesis of new diol lattice inclusion hosts.

The diols 7-11 have been synthesized, and their X-ray crystal structures determined, to learn how to influence and control lattice hydroxy group hydrogen bonding using crystal engineering ideas. To obtain new lattice inclusion hosts precise structural rules can be defined which enable the necessary supramolecular interactions to be duplicated. In this manner the helical tubuland 10 and ellipsoidal clathrate 11 hosts were obtained for the first time and their chloroform inclusion compounds characterized. New synthetic routes were utilized to obtain the bicyclo[3.3.2]decane and 9-thiatricyclo[4.3.1.1(3,8)]undecane frameworks present in these compounds. The solid-state conformations of bicyclo[3.3.2]decane derivatives 9 and 10 are compared with prior predictions and studies made on this uncommon ring system.

Pi-halogen dimers and V-shaped tetrahalo aryl inclusion hosts

1,4,8,11-Tetrabromo-5bα,6,12bα,13-tetrahydropentaleno[1,2-b:4,5-b′]diquinoline 6 has been synthesised and found to be an efficient lattice inclusion host for a range of small solvent molecules. The compound is a new example of the tetrahalo aryl host family, a group of molecules characterised by having a combination of inclined aromatic planes and halogen substitution at their extremities. The X-ray structures of (6)·(carbon tetrachloride) and (6)2·(allyl cyanide) are presented and discussed in crystal engineering terms. Both structures contain a common motif (the pi-halogen dimer) where two inversion-related host molecules pack such that one bromine atom from each is situated in the cleft of its V-shaped partner. This efficient packing motif provides a combination of π⋯Br and OFF (offset face–face) interactions within one supramolecular building block.

Synthesis of a new lattice inclusion host belonging to the tetrahalo aryl family

The tetrabromo diquinoline derivative 3 has been synthesised and its dichloromethane compound investigated by X-ray crystallography. This racemic host acts in an unusual manner by assembling into achiral molecular staircases and including the guests in parallel channels between these. Compound 3 belongs to a newly identified family of lattice inclusion hosts whose structural characteristics are described here for the first time.

Crystal Engineering Involving C−H···N Weak Hydrogen Bonds: A Diquinoxaline Lattice Inclusion Host with a Preference for Polychlorocarbon Guests

The di(1,8-naphthryridine) 7 and diquinoxaline 12 derivatives were synthesised as potential new lattice inclusion hosts where strong hydrogen bonding interactions would be absent. A number of potential supramolecular synthons (such as aryl face-face, aryl edge-face, halogen-halogen, C−H···N, nitrogen-halogen) were expected to be accessible, with competing combinations of these weak attractions providing the best (but probably different) type of host-guest structure in each case. While the former compound turned out to be unstable, the latter proved to be a versatile host which preferred to trap small polychloroalkane guests. The X-ray structures of 12·(chloroform)2, (12)2·(tetrahydrofuran), and (12)2·(1,1,2,2-tetrachloroethane) are reported and shown to have different lattice packing where the guests occupy layers, parallel tubes, and molecular boxes, respectively. The detailed interplay of the above synthons in forming these structures is described in crystal engineering terms. Most significantly, the C−H···N weak hydrogen bond plays a major role in all three inclusion structures. Both single linear and double cyclic interactions are involved in molecular edge-edge assembly of the host 12. Several new types of double cyclic interactions were discovered revealing that the C−H···N interaction is a key synthon for crystal engineering involving nitrogen heteroaromatic compounds.

A New Lattice Inclusion Host Involving Double-stranded Columns of Diol Molecules [1

Crystallization of dialcohol 4 from benzene yields an inclusion compound whose crystal structure [(C13H24O2)2·(C6H6), P21/c, a 7.918(2), b 13.505(2), c 14.924(5) Å, β 109.30(1)°, Z 2, R 0.069] shows that the host molecules are present as parallel doubly-stranded columns. Each column is constructed from one strand of (+)-, and a second of (-)-, enantiomers of 4. These two chirally pure strands are linked through a continuous chain of hydrogen bonding …O—H…O—H…O—H… to complete the column, and the benzene guests occupy interstitial sites between the parallel columns.

Designing new lattice inclusion hosts

Designing new lattice inclusion hosts

A Tetrachloro Guest in a Molecular Box

The new lattice inclusion host exo-7,exo-15-dibromo-6,7,14,15-tetrahydro-6,14-methanocycloocta[1,2-b:5,6-b'] diquinoxaline (6) has been synthesized in three steps from bicyclo [3.3.1]nonane-2,6-dione and benzofurazan oxide. It preferentially forms crystalline inclusion compounds with small polyhaloalkane guest molecules, and the crystal structure of the 1,1,2,2-tetrachloroethane compound [(C21H14N4Br2)2.C2H2Cl4, Pbcn , a 11.663(2), b 13.195(3), c 27.444(5) Ǻ, Z 4, R 0.041] is described. The key characteristic of this compound is a series of molecular boxes in which the guest molecules reside. Construction of the six surrounding walls is achieved with the aromatic rings of just four host molecules, and the guest molecule occupies a fixed position within the box. The intermolecular forces resulting in formation of this novel inclusion structure are analysed in detail.