Multi-component self-assembled heteroleptic Cu(I) complex with defective coordination site as a fluorescent probe to detect Zn2+

Heteroleptic copper(I)–phosphine complexes have attracted considerable attention due to their diverse structures and photophysical properties. In this work, a novel heteroleptic binuclear copper (I) complex C1·2BF4ˉ was designed and synthesized by using hexaazatriphenylene (L1) and 4, 5-Bis(diphenylphosphino)-9, 9-dimethylxanthene (dppd) as functional ligands. Such dinuclear structure with defective site was fully characterized by NMR, single-crystal X-ray diffraction analysis, and electron spray ionization mass spectrometry (ESI-MS). UV-vis and fluorescence spectrum revealed that the well-defined Cu(I) complex had a green emission at 518 nm in acetonitrile solution, and a red emission at 824 nm in the solid state. The DFT calculation demonstrated that the energy gap between LUMO and HOMO orbitals reached 1.20 eV. Furthermore, such heteroleptic Cu(I) complex showed high sensitivity and selectivity towards Zn2+ in acetonitrile solution in “turn-on” mode, which can be attributed to the coordination interaction between Zn2+ and defective binding site of probe C1·2BF4−. The LOD for Zn2+ was calculated to be 0.298 µM, and the reversible “on-off” fluorescence sensing behavior can be recovered by alternative treatment with EDTA tetrasodium and Zn2+ salts in solution. The Cu(I) complex probe C1·2BF4ˉ had reversible redox property with weak electrochemical responses towards Zn2+ ions.