A 6-connected {Cu2O5 )} cluster-based metal-organic framework based on tetrabromoterephthalate: synthesis, crystal structure and fluorescent properties

Abstract

An interseting Cu(II)-based organic framework containing a Cu₂O₅ cluster, [Cu (TBA)(CH₃OH)]_n (1) has been hydrothermally synthesized with tetrabromoterephthalate (H₂TBA) ligand. The X-ray single-crystal diffraction analysis shows that the Cu^II center is hexa-coordinated and situated on perfect octahedral geometry formed by four carboxyl oxygen atoms of four symmetry-related TBA²⁻ anions and two O-donors of two reverse µ₂-CH₃OH bridges. Each TBA²⁻ ligand plays as a µ₄ tetra-monodentate linker and connect four Cu²⁺ cations together to form the three dimensional structure of 1. Surprisingly, there are no significant hydrogen bonds and π-stack interactions in 1, but the Br···Br halogen bonds interactions. Detailed topology analysis found that the 3D cluster-based metal-organic framework of 1 can be simplified to 4 topological types: a 4,4-c 2-nodal {4²·8⁴} lvt topology, a 6,6-c 2-nodal {4¹³·6²}{4⁸·6⁶·8} FEQWOO topology, a 4,6-c 2-nodal {3²·6²·7²}{3⁴·4²·6⁴·7⁵} seh-4,6-Imma topology, and a 6,8-c 2-nodal {3⁴·4⁴·5⁴·6³}{3⁸·4¹⁴·5⁴·6²} new topology, respectively. Moreover, 1 exhibits intense solid-state luminescence emissions centered at 478 nm at room temperature, which mainly originates from the intraligand π→ π* transitions of TBA²⁻. The CCDC number of 1 is 2355788.