A Closed Metallomolecular Cage that can Open its Aperture by Disulfide Exchange

A closed metallomolecular cage based on the tris(saloph) framework, in which its aperture can be opened by disulfide exchange, was designed. At the apertures of the molecular cage, bridging diamine ligands having a disulfide bond were introduced to close the cage structure. These bridging ligands efficiently blocked the uptake of a guest, Cs⁺, but the presence of a thiolate anion significantly accelerated the guest uptake. This clearly means that this cage complex became open by the addition of the thiolate anion, because the cage closure becomes more dynamic due to the disulfide exchange reaction.     

Synthesis and crystal structure of a new Cu3Au‐type ternary phase in the Au–In–Pd system: distribution of atoms over crystallographic positions

A new Cu₃Au‐type ternary phase (τ phase) is found in the AuPd‐rich part of the Au–In–Pd system. It has a broad homogeneity range based on extensive (Pd,Au) and (In,Au) replacement, with the composition varying between Au_17.7In_25.3Pd_57.0 and Au_50.8In_16.2Pd_33.0. The occupancies of the crystallographic positions were studied by single‐crystal X‐ray diffraction for three samples of different composition. The sites with mm symmetry are occupied by atoms with a smaller scattering power than the atoms located on 4/mmm sites. Two extreme structure models were refined. Within the first, the occupation type changes from (Au,In,Pd)₃(Pd,In) to (Au,Pd)₃(In,Pd,Au) with an increase in the Au gross content. For the second model, the occupation type (Au,In,Pd)₃(Pd,Au) remains essentially unchanged for all Au concentrations. Although the diffraction data do not allow the choice of one of these models, the latter model, where Au substitutes In on 4/mmm sites, seems to be preferable, since it agrees with the fact that the homogeneity range of the τ phase is inclined to the Au corner and provides the same occupation type for all the studied samples of different compositions.     

Design of Hollow Protein Nanoparticles with Modifiable Interior and Exterior Surfaces

Protein‐based nanoparticles hold promise for a broad range of applications. Here, we report the production of a uniform anionic hollow protein nanoparticle, designated TIP60, which spontaneously assembles from a designed fusion protein subunit based on the geometric features of polyhedra. We show that TIP60 tolerates mutation and both its interior and exterior surfaces can be chemically modified. Moreover, TIP60 forms larger structures upon the addition of a cationic protein. Therefore, TIP60 can be used as a modifiable nano‐building block for further molecular assembly.     

Peripheral Templation‐Modulated Interconversion between an A4L6 Tetrahedral Anion Cage and A2L3 Triple Helicate with Guest Capture/Release

An anion‐coordination‐based A₄L₆ (“A” denotes anion and “L” is ligand) tetrahedral cage was constructed by a C₂‐symmetric bis‐bis(urea) ligand and phosphate anion, which showed reversible interconversion with the A₂L₃ triple helicate as a response to the template, concentration, or solvent. Notably, an unusual “peripheral” templation was found to be critical to stabilize the tetrahedral structure. This peripheral effect was utilized to assemble an “empty” A₄L₆ cage that allows the multi‐stimuli‐controlled capture/release of biologically important species such as choline and acetylcholine.     

Strained tridecane cage systems

Hexacyclo[6.5.0.0^2,7.0^4,12.0^5,10.0^9.13]tridecane (HCTD) contains two four-membered, two five-membered and two six-membered rings fused into a cage structure which contains about 77.0 kcal/mol of strain energy. Attempts to prepare the thioketal from the diketone of HCTD led to a skeletal rearrangement to produce a cage with one four-membered, four five-membered, and two six-membered rings fused into a cage (RHCTD). The corresponding RHCTD hydrocarbon has a strain energy 13.7 kcal/mol less than that of the starting tridecane (HCTD) which provides the driving force for the rearrangement. The X-ray structures of two HCTD derivatives and one RHCTD derivative are reported. The bond lengths in the three reported structures are normal for cages of this type. The structure of tetracyclo[6.3.0.0^3,7.0^4,11]undecane-5,10-dione mono(ketene 1,3-propanedithioacetal) is discussed also.