Self-Assembled Cage for In Situ Detecting Silver Cation in Water.

Here, a capsule-shaped cage comprising three monocationic arms was efficiently self-assembled by condensing a triscationic trisaldehyde and a trisamino linkage in water. Multivalence endows the cage with thermodynamic stability in water. Despite its triscationic nature, the cage is able to use its trisimino residue to coordinate a silver cation. As a comparison, other cations lead to cage decomposition or no coordination. The cage and Ag+-coordinated complex were both characterized and confirmed by NMR spectroscopy, mass spectrometry, and theoretical calculations. The metal-ligand complex exhibits a pale-yellow color that can be detectable by the naked eye. The Ag+-coordinated complex undergoes decoordination upon the addition of NaCl, during which the cage containing imine bonds remains intact. Such stability implies that the cage might be potentially employed in silver detection and mining.

Constraining Homo- and Heteroanion Dimers in Ultraclose Proximity within a Self-Assembled Hexacationic Cage.

A hexacationic cage 36+ was synthesized via hydrazone condensation in aqueous acid. Cage 36+ bears three biscationic arms, each of which contains four relatively acidic protons, including one NH and three CH protons. These hydrogen bond donors, as well as its intrinsic cationic nature, enable cage 36+ to encapsulate two anions concurrently within its cavity. The axial asymmetrical nature of the biscationic arms allow the cage to recognize two different anions in a selective manner, to encompass bound heteroanion dimers, such as Cl-·NO3- and Cl-·Br-. Single crystal X-ray diffraction analyses reveal that in the solid state the two anions are constrained in ultraclose proximity within the cage; e.g., the Cl-···Cl- and Cl-···Br- distances are 3.2 and 2.9 Å, respectively, which are shorter than the sum of their van der Waals radii. Evidence consistent with the sequential binding of two identical or disparate anions in CD3CN is also presented.

Regioselective B2-6 penta-iodination of the [CB11H12]- monocarborane cluster by palladium catalysis.

Penta-iodination of the B2-6 positions of the {CB11} monocarborane cluster is reported. Products of the structure [2,3,4,5,6-I5-CB11H6-12-X]- (X = H, Me, Et, Ph, Br, I) were obtained and fully characterized. X-ray crystal structures of three new compounds confirm this particular substitution pattern. The synthetic method relies on palladium catalysis/B-H activation, assisted by the C1-COOH directing group. The one-pot procedure enables penta-iodination and subsequent decarboxylation under convenient conditions. The B2-6 regioselectivity is complementary to the commonly observed reactivity of {CB11} clusters, which follows the trend B12 > B7-11 > B2-6 for electrophilic substitution. Thus, for the first time upper-belt halogenation is achieved without prior modification of the lower-belt positions.

A water-soluble naphthalenediimide-containing hexacationic cage.

A water-soluble cage containing three naphthalenediimide (NDI) units was synthesized in a one-pot manner without chromatographic purification, during which six irreversible C-N bonds formed simultaneously via an SN2 reaction. The cage was observed to be capable of accommodating a variety π-electron rich guests in a peripheral manner in water. However, for linear guests including I3- and I2, the cage is able to form an inclusion complex. Besides, in the solid state, the cage can absorb vapor of I2.