A CuBr Metal–Organic Framework: From Two Dimensional Net to Quasi-Three Dimensional Frame Through Encapsulated Cu2Br2 Cluster

Abstract

A new metal–organic framework of [(CuBrL1)(CuBr)0.25] (1) [L1 = 1,3,5-tris(4′-pyridyloxadiazole)-2,4,6-triethylbenzene] has been synthesized and characterized by single crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analyses and powder X-ray diffraction. As revealed by the single crystal X-ray diffraction, there exist one kind of L1 ligand and two kinds of (CuBr)x units in complex 1. L1 and the fully occupied CuBr monomer form a 3 × 3 two-dimensional wavelike net. Each 2D net is composed of two kinds of Cu-organic cycles, Cu4 with four Cu(I) centers and Cu2 with only two. The 2D nets are packed into 3D frameworks through π–π interactions in the AB fashion. This structure feature can be attributed to the flexibility of the tri-armed ligand. The second kind of CuBr unit is ca. 1/4 occupied Cu2Br2 dimer. From the viewpoint of host–guest chemistry, the Cu2Br2 dimer can be seen as a guest encapsulated in the Cu2 cycle through Br1–Cu2 coordination bond and Br2–π interactions. 1 displays typical dual photo-luminescence in the solid which can be assigned to the fixed ligands and CuBr clusters respectively. The CCDC number of 1 is 1958712.