FaFrit

RNA tetrahedral nanoparticles with two different sizes are successfully assembled by a one-pot bottom-up approach with high efficiency and thermal stability. The reported design principles can be extended to construct higher-order polyhedral RNA architectures for various applications such as targeted cancer imaging and therapy.

[Ni(cod)₂]-mediated intramolecular reductive coupling of β–β′ linked meso,meso′-dibromosubporphyrin dimer gave the anti-isomer of meso–meso′, β–β′ doubly linked subporphyrin dimer as the first example of a fused subporphyrin dimer. The fused dimer 3_anti displays an wavelike coplanar structure, a perturbed and red-shifted absorption spectrum, reversible redox behaviors with a decreased electrochemical HOMO–LUMO band gap, and a short S₁-state lifetime owing to the delocalized π-electronic network.

Link up: [Ni(cod)₂]-mediated intramolecular reductive coupling of a β–β′ linked meso,meso′-dibromosubporphyrin dimer gave the anti-isomer of a fused subporphyrin dimer. The new dimer displays a wavelike coplanar structure, a perturbed and red-shifted absorption spectrum, reversible redox behaviors with a decreased electrochemical HOMO–LUMO band gap, and a shortened S₁-state lifetime owing to the effective conjugation through fusion.

Although the major isomers of M@C₈₂ (namely M@C_2v(9)-C₈₂, where M is a trivalent rare-earth metal) have been intensively investigated, the lability of the minor isomers has meant that they have been little studied. Herein, the first isolation and crystallographic characterization of the minor Y@C₈₂ isomer, unambiguously assigned as Y@C_s(6)-C₈₂ by cocrystallization with Ni(octaethylporphyrin), is reported. Unexpectedly, a regioselective dimerization is observed in the crystalline state of Y@C_s(6)-C₈₂. In sharp contrast, no dimerization occurs for the major isomer Y@C_2v(9)-C₈₂ under the same conditions, indicating a cage-symmetry-induced dimerization process. Further experimental and theoretical results disclose that the regioselective dimer formation is a consequence of the localization of high spin density on a special cage-carbon atom of Y@C_s(6)-C₈₂ which is caused by the steady displacement of the Y atom inside the C_s(6)-C₈₂ cage.

It takes two: The dimerization of a pristine metallofullerene is observed for the first time in the crystal structure of the labile minor isomer of Y@C₈₂, unambiguously assigned as Y@C_s(6)-C₈₂. In contrast, under identical conditions the major isomer Y@C_2v(9)-C₈₂ does not form dimers, indicative of a cage-symmetry-induced process which can be rationalized by considering the localization of spin densities on the fullerene cages.

Simple discotic cores functionalized with reactive arms have been assembled into two- and three-tiered covalent stacks through imine formation. The targets are obtained in good yields, but competing formation of misassembled byproducts highlights some of the challenges inherent to the thermodynamically controlled assembly of rigid, compact, three-dimensional architectures. The structures comprise a central stack of arenes surrounded by a triple helix of interconnected arms. The racemization rate is strongly dependent on the number of tiers, suggesting cooperative conformational coupling in these multi-tiered structures.

Discrete stacks: Two- and three-tiered covalent compounds are obtained through imine condensation. The final structures, formally fused cages, comprise a central stack of arenes embedded within a triple helix. The rate of racemization depends strongly on the number of tiers because of conformational coupling in these highly interconnected structures.