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

CrystEngComm Pub Date: 2022-03-16 DOI: 10.1039/D2CE00128D

Abstract

Two coordination polymers (CPs), [Cu2(L1)(μ3-OH)(H2O)]n (1) and {[Zn4(L)2(4,4′-bipy)3]·4H2O}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 (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 μs) was obtained using the formula [(A1 × τ12) + (A2 × τ22)]/(A1 × τ1 + A2 × τ2).

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