Glucose Binding Drives Reconfiguration of a Dynamic Library of Urea-Containing Metal-Organic Assemblies.

A bis-urea-functionalized ditopic subcomponent assembled with 2-formylpyridine and FeII , resulting in a dynamic library of metal-organic assemblies: an irregular FeII4 L6 structure and three FeII2 L3 stereoisomers: left- and right-handed helicates and a meso-structure. This library reconfigured in response to the addition of monosaccharide derivatives, which served as guests for specific library members, and the rate of saccharide mutarotation was also enhanced by the library. The (P) enantiomer of the FeII2 L3 helical structure bound β-D-glucose selectively over α-D-glucose. As a consequence, the library collapsed into the (P)-FeII2 L3 helicate following glucose addition. The α-D-glucose was likewise transformed into the β-D-anomer during equilibration and binding. Thus, β-D-glucose and (P)-3 amplified each other in the product mixture, as metal-organic and saccharide libraries geared together into a single equilibrating system.European Research Council (695009), UK Engineering and Physical Sciences Research Council (EPSRC EP/P027067/1), National Natural Science Foundation of China (No. 21971210), Natural Science Foundation of Shaanxi Province (2019KJXX-062) and the Chinese Scholarship Council (CSC), the Alexander von Humboldt Foundation for a Feodor Lynen Research Fellowship, the Rashkind Family Endowment, the Chenery Endowment, and the Donors of the American Chemical Society Petroleum Research Fun

Hopping protons in supramolecular catalysis

Supramolecular catalysis can emulate many features of enzymatic transformations. Now, a complex proton wire mechanism — enabling the dual activation of a nucleophile and an electrophile through reciprocal proton transfer — has been shown to operate during the β-glycosylation of sugars within a self-assembled capsule

Host Spin‐Crossover Thermodynamics Indicate Guest Fit

Funder: Cambridge Trust; Id: http://dx.doi.org/10.13039/501100003343Funder: Newnham College, University of Cambridge; Id: http://dx.doi.org/10.13039/501100000663Spin‐crossover (SCO) metal‐organic cages capable of switching between high‐spin and low‐spin states have the potential to be used as magnetic sensors and switches. Variation of the donor strength of heterocyclic aldehyde subcomponents in imine‐based ligands can tune the ligand field for a FeII center, which results in both homoleptic and heteroleptic cages with diverse SCO behaviors. The tetrahedral SCO cage built from 1‐methyl‐1H‐imidazole‐2‐carbaldehyde is capable of encapsulating various guests, which stabilize different cage spin states depending on guest size. Conversely, the SCO tetrahedron exhibits different affinities for guests in different spin states, which is inferred to result from subtle structural differences of the cavity caused by the change in metal center spin state. Examination of SCO thermodynamics across a series of host–guest complexes enabled sensitive probing of guest fit to the host cavity, providing information complementary to binding‐constant determination

Host Spin-Crossover Thermodynamics Indicate Guest Fit.

Funder: Cambridge Trust; Id: http://dx.doi.org/10.13039/501100003343Funder: Newnham College, University of Cambridge; Id: http://dx.doi.org/10.13039/501100000663Spin-crossover (SCO) metal-organic cages capable of switching between high-spin and low-spin states have the potential to be used as magnetic sensors and switches. Variation of the donor strength of heterocyclic aldehyde subcomponents in imine-based ligands can tune the ligand field for a FeII center, which results in both homoleptic and heteroleptic cages with diverse SCO behaviors. The tetrahedral SCO cage built from 1-methyl-1H-imidazole-2-carbaldehyde is capable of encapsulating various guests, which stabilize different cage spin states depending on guest size. Conversely, the SCO tetrahedron exhibits different affinities for guests in different spin states, which is inferred to result from subtle structural differences of the cavity caused by the change in metal center spin state. Examination of SCO thermodynamics across a series of host-guest complexes enabled sensitive probing of guest fit to the host cavity, providing information complementary to binding-constant determination

LaIII and ZnII Cooperatively Template a Metal-Organic Capsule.

An organic subcomponent was designed with 2-formyl-8-aminoquinoline and triazole-pyridine ends. The relative orientations and geometries of these two ends enabled this subcomponent to assemble together with ZnII and LaIII cations to generate a heterobimetallic tetrahedral capsule. The LaIII cations each template three imine bonds that hold together a 3-fold-symmetric metallo-ligand, defining the center of each tetrahedron face. The ZnII cations occupy the other ends of these C3 axes, defining the vertices of the tetrahedron. This is the first example where subcomponent self-assembly brought into being the faces of a polyhedron, as opposed to the vertices. Host-guest studies show positively cooperative binding toward ReO4-, the encapsulation of which also resulted in the quenching of capsule fluorescence.European Research Council (695009), UK Engineering and Physical Sciences Re- search Council (EPSRC EP/P027067/1), National Natural Science Foundation of China (No. 21971210), Natural Science Founda- tion of Shaanxi Province (2019KJXX-062), Chinese Scholarship Council (CSC), Alexander von Humboldt Foundation for a Feodor Lynen Re- search Fellowshi

Oxidation triggers guest dissociation during reorganization of an FeII 4L6 twisted parallelogram.

A three-dimensional FeII 4L6 parallelogram was prepared from ferrocene-containing ditopic ligands. The steric preference of the bulky ferrocene cores towards meridional vertex coordination brought about this new structure type, in which the ferrocene units adopt three distinct conformations. The structure possesses two distinct, bowl-like cavities that host anionic guests. Oxidation of the ferrocene FeII to ferrocenium FeIII causes rotation of the ferrocene hinges, converting the structure to an FeII 1L1 + species with release of anionic guests, even though the average charge per iron increases in a way that would ordinarily increase guest binding strength. The degrees of freedom exhibited by these new structures - derived from the different configurations of the three ligands surrounding a meridional FeII center and the rotation of ferrocene cores - thus underpin their ability to reconfigure and eject guests upon oxidation

Light-Powered Reversible Guest Release and Uptake from Zn4L4 Capsules.

A strategy for light-powered guest release from a tetrahedral capsule has been developed by incorporating azobenzene units at its vertices. A new Zn4L4 tetrahedral capsule bearing 12 diazo moieties at its metal-ion vertices was prepared from a phenyldiazenyl-functionalized subcomponent and a central trialdehyde panel. Ultraviolet irradiation caused isomerization of the peripheral diazo groups from the thermodynamically preferred trans configuration to the cis form, thereby generating steric clash and resulting in cage disassembly and concomitant guest release. Visible-light irradiation drove cage re-assembly following re-isomerization of the diazo groups to the trans form, resulting in guest re-uptake. A detailed 19F NMR study elucidated how switching led to guest release: each metal vertex tolerated only one cis-azobenzene moiety, with further isomerization leading to cage disassembly

Planning a family

We have all either been asked or seen others asked: “So when are you going to have children?” — at family gatherings, as a casual aside by colleagues or even by complete strangers. There is societal judgement around having children, not having children, when to have children and how many children to have. Even if we put aside the recent US Supreme Court decision to overturn Roe v Wade, 1973 and with it remove long-held rights around access to abortion in the US, there are numerous other ways in which reproductive choices are becoming weaponized, and what may seem to some an innocuous question is racialized, gendered and loaded