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

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

Two pairs of divalent and tetravalent porphyrin building blocks carrying the complementary supramolecular crown ether/secondary ammonium ion binding motif have been synthesized and their derived pseudorotaxanes have been studied by a combination of NMR spectroscopy in solution and ESI mass spectrometry in the gas phase. By simple mixing of the components the formation of discrete dimeric and trimeric (metallo)porphyrin complexes predominates, in accordance to binding stoichiometry, while the amount of alternative structures can be neglected. Our results illustrate the power of multivalency to program the multicomponent self-assembly of specific entities into discrete functional nanostructures

Gating the photochromism of an azobenzene by strong host–guest interactions in a divalent pseudo[2]rotaxane

The ability of an E-configured azobenzene guest to undergo photoisomerisation is controlled by the presence of a complementary host. Addition of base/acid allowed for a weakening/strengthening of the interactions in the divalent pseudo[2]rotaxane complex and hence could switch on/off photochromic activity.Peer Reviewe

Thermodynamic Analysis of Allosteric and Chelate Cooperativity in Di- and Trivalent Ammonium/Crown-Ether Pseudorotaxanes

A detailed thermodynamic analysis of the axle-wheel binding in di- and trivalent secondary ammonium/[24]­crown-8 pseudorotaxanes is presented. Isothermal titration calorimetry (ITC) data and double mutant cycle analyses reveal an interesting interplay of positive as well as negative allosteric and positive chelate cooperativity thus providing profound insight into the effects governing multivalent binding in these pseudorotaxanes

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