Host‐Guest Chemistry of Self‐Assembled Hemi‐Cage Systems: The Dramatic Effect of Lost Pre‐Organization

Abstract

New hemi‐cage compounds with the formula Pd2(L1)2(L2)2 (L1=ditopic pyridine ligand, L2=bpy or TMEDA) have been synthesized and characterized by spectroscopic methods, X‐ray crystallography and electronic structure methods. The host‐guest chemistry of these new structures, with naphthoquinone as a guest, reveals the key role of the host shape and flexibility on competitive binding processes. The influence of counteranions, solvent and non‐covalent interactions to binding were quantified by Density Functional Theory calculations. Together, this study provides new insights into the concept of pre‐organized guest binding when applied to charged, coordination‐assembled hosts.

Kinetic selection of Pd4L2 metallocyclic and Pd6L3 trigonal prismatic assemblies

“…poor access) factors. 16,19 In conclusion, we have shown how different multicomponent assemblies can be made using cis-capping ligands to tune the reversibility of M-L interactions, facilitating access to both kinetic and thermodynamic products. We continue the search for suitable guests that will allow the overall goal of creating simple, multi-cavity systems, in which catalysis can be controlled via allosteric binding.…”

“…[16][17][18] Moreover, we have also been interested in creating systems that provide a more open cavity, such as Pd 2 L 2 hemi-cage, HC (Fig. 1b), 19 which would permit better access to reactants and thus widen the substrate scope. We were also interested in creating structures which possess the features of the hemi-cage system i.e.…”

Unlocking the computational design of metal–organic cages

“…Conformationally flexible ligands decrease the preorganisation in a system, which can result in unexpected topological outcomes and a knock-on effect on properties. [46][47][48][49] Computational design of systems with flexible ligands is an additional challenge because it increases the degrees of freedom in the structure/property prediction.…”

“…The design of MOCs for catalysis focuses on tuning of the cavity microenvironment to optimise reaction conditions, akin to designing synthetic enzymes. 48,161,162 The role of a MOC in catalysing a reaction is often linked to their affinity for the reactant(s), transition state, or product(s). MOC catalysis can be the result of internal or external chemistry, and/or confinement effects.…”

Rationalizing the “Diels-Alderase” Activity of Pd2L4 Self-Assembled Metallocages: Enabling the Efficient Prediction of Catalytic Scaffolds

“…In both cases, and as previously seen for Lewis acid-catalyzed [4+2] cycloadditions, [71][72][73] the cages enhance the electrophilic character of the dienophile bound in the cavity. Polarization of the dienophile within the cage leads to a net charge of +0.25 and +0.16 in bq for C-1 and C-2, respectively ( Figure S14), 74 leading to a lowering the LUMO energy by 1.6 / 1.5 eV in C-1 and C-2, respectively. This suggests that small differences in the cage building blocks can lead to differences in the polarizing properties of the two cages.…”