James M. A. Robinson

Weak interactions in crystal engineering—understanding the recognition properties of the nitro group

1,3,5-Trinitrobenzene and 1,3,5-triethynylbenzene cocrystallise to form a solid state structure in which the two components assemble to form segregated hydrogen-bonded tapes. This behaviour is rationalised, through the use of the Cambridge Structural Database and ab initio electronic structure calculations, in terms of the fundamental recognition properties of the nitro group. The recognition behaviour of the nitro group is a function of both the intrinsic electronic properties of the nitro group itself and the nature of the hydrogen bond donor with which it interacts.

Bromonitrile oxide [3+2] cycloadditions in water

Abstract Bromonitrile oxide can be generated homogeneously in water at acidic pH, allowing efficient [3+2] cycloaddition with water soluble olefins and acetylenes. Allylammonium salts react with high regioselectivity and without the need for N-group protection.

A NEW HYDROGEN BONDING MOTIF BASED ON 10-HYDROXY-10,9-BORAZAROPHENANTHRENE

Abstract The rational design of a system which mimics the molecular recognition properties of carboxylic acids but displays markedly different reactivity is presented. 10-Hydroxy-10,9-borazarophenanthrene is predicted by both structural analogy with carboxylic acids and ab initio calculations to form cyclic hydrogen bonded homodimers and its crystal structure demonstrates that this expectation is fulfilled. In solution, however, the reactivity of 10-hydroxy-10,9-borazarophenanthrene is markedly different from that of carboxylic acids - reacting with itself under certain conditions by nucleophilic addition at boron followed by loss of water to form the corresponding anhydride. This reactivity is rationalised in terms of the electronic structure of the borazarophenanthrene system.

Crystal Engineering Based on Nitro Derivatives of 10-Hydroxy-10,9-borazarophenanthrene

The steric and molecular recognition properties of the nitro group control the molecular packing of 10-hydroxy-10,9-borazarophenanthrene derivatives facilitating the formation of stepped hydrogen bonded molecular tapes of 8-nitro-10-hydroxy-10,9-borazarophenanthrene and cyclic homodimers of 6-nitro-10-hydroxy-10,9-borazarophenanthrene.

INTERCHANGEABILITY OF HALOGEN AND ETHYNYL SUBSTITUENTS IN THE SOLID STATE STRUCTURES OF DI- AND TRI-SUBSTITUTED BENZENES

Examination of the solid state structures of bromo- and fluoro-substituted ethynylbenzenes, determined by single crystal X-ray diffraction, has demonstrated that the halogen and ethynyl substituents on these 1,4- and 1,3,5-substituted benzene rings can be interchanged without significant changes in their average solid state structures. Consideration of these structures, together with those of 1,4- and 1,3,5-substituted halogenobenzenes, suggests that, in most cases, shape complementarity may be of equal importance to interactional complementarity when attempting to rationalise the packing of these molecules in the solid state.

PREDICTABLE SOLID STATE STRUCTURES INCORPORATING THE CC-H...O2N SUPRAMOLECULAR SYNTHON

Terminal alkynes interact with nitro groups in a symmetrically bifurcated manner to form ribbon-like structures in the solid state.

A borazaaromatic analogue of isophthalic acid

A diboradiazaaromatic—2,7-di-tert-butyl-5,9-dihydroxy-5,9-dibora-4,10-diazapyrene-4,10-diium-5,9-diuide—which is a structural analogue of isophthalic acid has been designed and synthesised. This compound is capable of spontaneous dehydration in solution to form linear oligoanhydrides. These oligoanhydrides can be readily hydrolysed to the starting diboradiazaaromatic under appropriate conditions. This unusual reactivity is mirrored in the solid-state behaviour of 2,7-di-tert-butyl-5,9-dihydroxy-5,9-dibora-4,10-diazapyrene-4,10-diium-5,9-diuide. A complex network of hydrogen bonds present in the solid-state structure of the borazaaromatic serve to facilitate a facile solid-state dehydration reaction, once again forming oligoanhydrides of molecular weight greater than 3000 Da.