Guest Binding and Catalysis in the Cavity of a Cubic Coordination Cage

Abstract

Mike Ward studied in Cambridge for his BA and Ph.D. before a post-doc position in Strasbourg with Jean-Pierre Sauvage. His independent academic career started with a lectureship in Bristol from 1990, and he remained there for 13 years before moving to Sheffield as a Professor of Inorganic Chemistry in 2003. His research interests cover many aspects of transition-metal and lanthanide ion coordination and supramolecular chemistry.Chris Hunter is the Herchel Smith Professor of Organic Chemistry at the University of Cambridge. After a BA and then Ph.D. in Cambridge, he started his academic career as a lecturer at the University of Otago in New Zealand and then worked at the University of Sheffield for 23 years before taking up his current post in 2014. He has research interests in various aspects of supramolecular and physical organic chemistry.Nick Williams did his BA, Ph.D., and early post-doctoral work in Cambridge. In 1994 he went to McGill University in Montréal as a RS/NSERC Research Fellow, working with Prof. J. Chin. In 1996 he was appointed to a lectureship at the University of Sheffield, where he has remained. His interests are in physical organic chemistry, working on understanding reactivity, mechanism, and catalysis in a range of contexts from organic surfaces to biological catalysis. These insights have underpinned the creation and understanding of a variety of biomimetic and supramolecular systems. AbstractAn M 8 L 12 coordination cage, which is water-soluble but has a hydrophobic interior cavity, is an effective host for a wide range of small organic guests; the factors responsible for guest binding have been investigated in detail. Benzisoxazole is a competent guest and, when bound, undergoes the Kemp elimination reaction with a rate acceleration of up to 2 © 10 5 times compared to the reaction of unbound benzisoxazole; the reasons for this have been analyzed.

Interaction of anions with the surface of a coordination cage in aqueous solution probed by their effect on a cage-catalysed Kemp elimination

“… 4 As part of our work in this area using an octanuclear cubic M 8 L 12 cage ( Fig. 1 ), 5 we have demonstrated that the accumulation of counter-ions around the exterior surface of a cationic cage is just as important a phenomenon as the binding of neutral guest molecules inside the cavity. 6–10 This is a conclusion that has also been reached by others who have demonstrated how interactions of metal/ligand cage assemblies with counter-ions at the exterior surface can play fundamentally important roles in controlling structure and speciation behaviour of cage assemblies, as well as their ability to bind guests in the central cavity.…”

Interplay of water and a supramolecular capsule for catalysis of reductive elimination reaction from gold

“…Inspired by the ultimate enzyme catalyst 1,2 , supramolecular catalytic systems seek to be biomimetic 3,4,5 for features such as presence of an active site 6 with optimized non-covalent interactions with the substrate, 7 electrostatic preorganization that eliminates the reorganization cost paid by the uncatalyzed reaction, 8,9 as well as desolvation and dynamical effects that are relevant for the complete catalytic cycle. 10,11,12 In turn, the weak intermolecular interactions that govern supramolecular assemblies offer the undeniable advantage of easy functionalization, reversibility, and fast self-assembly 5,13,14 that overcome limitations of a delicate and more difficult redesign of an enzyme scaffold 15 . Supramolecular catalysts have the potential to revolutionize the chemical industry by allowing simpler and more flexible reaction pathways that offers lower cost, reduces the creation of undesired byproducts 16,17,18,19 , operates in a broad range of conditions.…”

Application of Crystalline Matrices for the Structural Determination of Organic Molecules

“…104 − 106 Coordination cages as preformed crystalline matrices have recently been used for host–guest studies consistent with the crystalline sponge method. 107 When Ward et al encountered difficulty in obtaining host–guest structures using a [Co 8 L 12 ](BF 4 ) 16 cage with naphthyl-based bis-bidentate bridging ligands via cocrystallization, they used preformed crystals of the cage for soaking, 108 where neat cycloundecanone (with minimal MeOH to prevent crystal desolvation) was trapped and observed. Other studies with a similar cage led to the observation of adamantane-1-carboxylic acid and alkyl-phosphonate chemical warfare agent simulants via SC-XRD.…”

“…For Co-based cage synthesis, upon performing a one-step synthesis of the bis-bidentate ligand, crystals can be conventionally grown in 7 d or in 12 h via a solvothermal method yielding higher-quality larger crystals. 112 , 113 Soaking experiments for MOPs have been reported in as short as a few minutes versus 2–4 d reported with MOFs, 107 providing another potential benefit of using MOPs.…”