Synthesis, crystal structure, fluorescence and electrochemical properties of two Ag(I) complexes based on 2-(4′-pyridyl)-benzoxazole/SPPh₃ ligands

Abstract

To explore the luminescence properties of silver complexes in the solid state, two Ag(I) complexes, [Ag(4-PBO)₂(NO₃)] {di[2-(4′-pyridyl)-benzoxazole]silver(I) nitrate} (1) and [Ag₂(SPPh₃)₄](ClO₄)₂ {[tetra(triphenylphosphine sulfide)disilver(I)] diperchlorate} (2) (4-PBO =2-(4′-pyridyl)-benzoxazole, SPPh₃ = triphenylphosphine sulfide), have been synthesized and characterized by elemental analysis, FT-IR and UV-Vis spectroscopy. Single-crystal X-ray diffraction revealed that 1 is three-coordinate by two nitrogen atoms from two 4-PBO ligands and an oxygen atom from the coordinated nitrate anion forming a triangular plane configuration. In 2, the SPPh₃ ligands adopt a monodentate coordinated and monoatomic bridging mode to connect two Ag(I) ions, resulting in a three-coordinate symmetrical binuclear structure. In the solid state, the luminescence properties of the ligands 4-PBO, SPPh₃ and their complexes were investigated. The results demonstrated that 1 results in the fluorescence quenching of aggregates due to the strong π–π stacking effect. The fluorescence enhancement of 2 may be attributed to the “aggregation-induced emission” (AIE) effect of restricted intramolecular rotations of the peripheral phenyl rings against the central core. In addition, cyclic voltammograms of 1 and 2 indicated an irreversible Ag⁺/Ag couple.

Graphical Abstract

Keywords:

• silver(I) complex
• 2-(4′-pyridyl)-benzoxazole
• SPPh3
• crystal structure
• fluorescence

Additional information

Funding

The present research was supported by the Foundation of A Hundred Youth Talents Training Program of Lanzhou Jiaotong University [grant number 152022]; Natural Science Foundation of Gansu Province [grant number 17JR5RA090]; National Natural Science Foundation of China [grant number 21367017]; The Development of Instrument & Equipment Function and Technical Innovation Project of CAS [grant number 2018gl03].