Covalent Cages Research Articles

Templated synthesis of a large and flexible covalent porphyrinic cage bearing orthogonal recognition sites

A large covalent cage incorporating two porphyrins attached by four long and flexible polyether chains each bearing two 3-pyridyl ligands was synthesized from a DABCO-templated olefin metathesis reaction. The X-ray structure of the cage with the DABCO coordinated inside the cavity to the two zinc(II) porphyrins reveals a highly symmetric structure.

First-principles study of CrB4 as a high shear modulus compound

First-principles calculations were carried out to investigate the synthesized orthorhombic CrB4. Our calculations show that the shear modulus of orthorhombic CrB4 is much higher than that of superhard WB4. Moreover, its shear modulus is larger than its bulk modulus. Boron atoms in CrB4 form a strong covalent cage which dramatically increases its mechanical strength. The calculated elastic constants imply that CrB4 is elastically stable. The calculated density of states shows that CrB4 is metallic. The appearance of pesudogap near the Fermi level means that CrB4 is a stable compound. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)