Zn/Cu complexes constructed through selective in situ Br-Cl exchange: synthesis, structures, properties, and DFT insights into the Cu-catalyzed mechanism

Two coordination polymers (CPs), (Cu-2(L-1)(mu(3)-OH)(H2O)](n) (1) and {[Zn-4(L)(2)(4,4'-bipy)(3)]center dot 4H(2)O}(n) (2), were synthesized under solvothermal conditions. Unexpectedly, the transformation of aryl-Br to aryl-Cl (Br-Cl exchange) was observed in the formation of complex 1, which was successfully proven via energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Strikingly, Cu(n) ions were utilized as both coordinated atoms and as a catalyst for the in situ Br-Cl exchange in the process. In contrast, 5-(3-bromo-4-carboxyphenoxy)isophthalic acid (H3L) did not exhibit any change in complex 2. Moreover, the Br-Cl exchange mechanism on aromatic rings of H3L was investigated using density functional theory (DFT) calculations. More importantly, selective in situ metal/ligand reactions are important for the discovery of new ligands and synthetic organic chemistry. In addition, complex 1 exhibits a (3,6)-connected topological network, which shows dominant antiferromagnetic exchange in the tetranuclear Cu(II) unit. Complex 2 shows a (3,4,5)-connected topology with strong fluorescence intensity and its fluorescence lifetime (16.0 mu S) was obtained using the formula I(A(1) x tau(2)(1)) + (A(2) X tau(2)(2))]/(A(1) x tau(1) + A(2) X tau(2)).