Roger Bishop

New types of helical canal inclusion networks

Over recent years a variety of new helical canal inclusion systems have been discovered and characterised, and an increasing awareness has developed of the roles played by canal topology and helicity in the function of certain biological systems.

Analysis of pi–halogen dimer interactions present in a family of staircase inclusion compounds

The family of staircase inclusion compounds formed by the tetrahalo aryl hosts 1 and 2 are re-evaluated in terms of the pi–halogen dimer interactions present in their structures.

Pi–halogen dimer interactions and the inclusion chemistry of a new tetrahalo aryl host

The preparation of 1,4,8,11-tetrabromo-5b[small alpha],6,12b[small alpha],13-tetrahydropentaleno[1,2-b:4,5-b[prime or minute]]diquinoline is described. This is a further member of the tetrahalo aryl host family, and forms crystalline lattice inclusion compounds with many guests. The X-ray structures of the allyl cyanide, 1,2,3-trichloropropane, chlorobenzene, toluene, benzene-water, methyl chloroform and carbon tetrachloride inclusion compounds are described, and compared with that of the solvent-free apohost. Although several different structural types are produced, the recently reported pi-halogen dimer (PHD) interaction plays an important role in all of these, except for that of pure (where the packing energy is the least favourable of the series).

The Pi – Halogen Dimer (PHD) Interaction: A Versatile New Construction Unit for Crystal Engineering

ABSTRACT The pi – halogen dimer (PHD) interaction is a new type of intermolecular packing motif discovered in certain crystalline diquinoline compounds. It consists of a combination of one aromatic offset face-face (OFF) interaction, and four aromatic pi – halogen interactions, and provides a compact building block for the self-assembly of lattice inclusion compounds. This article reviews the current state of knowledge about this new solid-state construction motif.

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

Abstract 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.

Solid-state regio- and stereo-selective benzylic bromination of diquinoline compounds using N-bromosuccinimide

Solvent-free N-bromosuccinimide (NBS) bromination of diquinoline derivatives reveals that benzylic bromination takes place in a regio- and stereo-selective manner in the absence of toxic and ozone-depleting CCl4 solvent.

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.

Ritter-type Reactions

The process now known as the Ritter reaction was first described in detail in two papers1,2 published in 1948. Strongly acidic conditions were used to generate a carbenium ion which underwent nucleophilic attack by a nitrile, and further events leading to the isolated product. In its original and most familiar form, hydrolytic work-up produced an amide. However, later investigations showed that in suitable cases intramolecular cyclization could occur, affording a wide range of heterocyclic materials. Although this very general reaction is justly named for Ritter, who recognized and explored its considerable potential, it is not surprising that a few special cases of Ritter-type processes are described in earlier independent reports.3–7 Early work on the Ritter reaction is well served by a number of review articles,8–14 that by Krimen and Cota12 being especially valuable in the present context.

Molecular Solids Formed by the Self‐Organisation of Dialcohols into Hydrogen‐Bonded Ladders

The ability of certain dialcohols to form solid-state structures containing unidirectional hydrogen-bonded ladders has been investigated. Two double-stranded structures, staircase-ladders and step-ladders, have been identified. In each, dialcohol molecules are hydrogen-bonded into linear strands with two parallel strands cross-linked through additional hydrogen bonding. Staircase-ladders are made up of (O−H)n chains of hydrogen bonds, with the molecules in the two strands out of phase with each other. Step-ladders are formed from (O−H)4 cycles of hydrogen bonds, with the molecules of the two strands in phase. Sixteen examples of staircase-ladder structures and twelve cases of step-ladder structures were identified by use of the Cambridge Structural Database. A further three examples, all shown to be staircase-ladders by single-crystal X-ray analysis, were synthesised. Distinct structural preferences in ladder formation can be identified. Nearly all staircase-ladders contain only one type of enantiomer, with the dialcohol building blocks arranged around a twofold screw axis. This type of ladder is thus favoured for enantiomerically pure compounds. The preferred step-ladder construction contains (+)-enantiomers in one strand and (−)-enantiomers in the other, giving two repeating centres of symmetry along the ladder axis. There are, however, many exceptions to this norm. These two ladder types are compared with each other and with those formed by organic molecules containing other hydrogen-bonding functionalities.

Prediction and structure of polymorphic lattice inclusion compounds of 2,7-dimethyltricyclo[4.3.1.03,8]undecane-syn-2,syn-7-diol

Abstract The host molecule 2,7-dimethyltricyclo[4.3.1.03,8]undecane-syn-2,syn-7-diol 1 is known to form two different structural types of lattice inclusion compound dependent on the guest molecule chosen. Guests, including 1,2-dichlorobenzene 2, have now been predicted which result in the formation of both lattice types according to the crystallisation conditions employed. Crystal structures of the ellipsoidal clathrate type: (Racemic-1)4.(1,2-Dichlorobenzene), space group I41/acd; and the helical tubulate type: (Resolved-1)3.(1,2-Dichlorobenzene), space group P3121 are presented. The latter polymorph is transformed into the former on heating in a sealed system.