Ligand conformation directed self-assembly of heteroleptic Cu(I) complexes and luminescent sensing properties for Zn2+

Abstract

Heteroleptic Cu(N^N)(P^P) complexes have garnered significant attention owing to their various structures and remarkable photophysical properties. Four novel heteroleptic copper(I) complexes (C1•2BF4ˉ, C2•3BF4ˉ, C3•3PF6ˉ and C4•3PF6ˉ) of the type {(Cu(P^P))3(μ-HATN)} synthesized by ligand conformation-directed self-assembly methodology were reported herein. These copper(I) complexes with different coordination configuration could be obtained through a straightforward change in the rigidity and volume in different P^P ligand scaffolds. Furthermore, these copper(I) complexes exhibited exceptional visible light absorption, which were contributed to metal-to-ligand charge transfer and intra-ligand charge transfer. Moreover, these emissive heteroleptic Cu(I) complexes all displayed remarkable sensitivity and selectivity towards zinc ions in “turn-on” mode (intensity enhanced ca.60 times). The detection limitation of complex C1•2BF4ˉ reached to 5.10 × 10−9 M, which was lower than those reported fluorescent sensors. The possible sensing mechanism was investigated using ESI-Ms, NMR and DFT calculation. The reversible “on-off” fluorescent sensing behavior can be restored by treating the solution alternately with EDTA tetrasodium salt and Zn2+ salt.