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 )(μ 3 -OH)(H 2 O)] n (1) and {[Zn 4 (L) 2 (4,4′-bipy) 3 ]·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( ii ) 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 (H 3 L) did not exhibit any change in complex 2. Moreover, the Br–Cl exchange mechanism on aromatic rings of H 3 L 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 μs) was obtained using the formula [( A 1 × τ 1 2 ) + ( A 2 × τ 2 2 )]/( A 1 × τ 1 + A 2 × τ 2 ).