Self-Assembly of a CsCl-like 3D Supramolecular Network from [Zn₆(HL)₆(H₂L)₆]⁶⁺ Metallamacrocycles and (H₂O)₂₀ Clusters (H₂L = 4-(2-Pyridyl)-6-(4-pyridyl)-2-aminopyrimidine)

Abstract

The reaction of Zn(NO3)2·6H2O with multifunctional ligand 4-(2-pyridyl)-6-(4-pyridyl)-2-aminopyrimidine (H2L) leads to a circular hexanuclear zinc complex [Zn6(HL)6(H2L)6](NO3)6·26H2O (1), confirmed by single-crystal X-ray diffraction. In the [Zn6(HL)6(H2L)6]6+ cation, six zinc centers are arranged in a chairlike conformation and 12 ligands fulfill bridging and terminal functions, respectively. The particular interest of complex 1 is the formation of a unique water cluster (H2O)26 composed of a clathrate (H2O)20 core and six dangling water molecules, and the clathrate (H2O)20 core is structurally similar to the famous “Bucky water” (H2O)20. Furthermore, the water molecules and the nitrate ions are assembled into an interesting negative three-dimensional (3D) framework through hydrogen bonds, and the [Zn6(HL)6(H2L)6]6+ cations just locate in the cavities of the anionic 3D network. To gain insight into the stability of (H2O)20 observed in complex 1, we isolate the water cluster from its environments and compare its stability with “Bucky water” (H2O)20 by a theoretical calculation method. Complex 1 displays room temperature photoluminescence