Thiacalix[4]arene-protected alkynyl Agn (n = 9, 18) nanoclusters: syntheses, structural characterizations, photocurrent responses and fluorescence properties

Abstract

Two thiacalix[4]arene-protected silver(I) alkynyl nanoclusters, [Na₂(H₂O)₂][Ag₉(TC4A)(^tBuCC)₄(CH₃OH)₂(SbF₆)_0.5(OH)_2.5]·3.5H₂O·CH₃OH (1, abbreviated as Ag₉) and [Ag₉(TC4A)(^tBuCC)₄(CF₃COO)]₂·4CH₃OH (2, abbreviated as Ag₁₈), were synthesized by the reaction of [^tBuCCAg]_n, p-tert-butylthiacalix[4]arene (H₄TC4A), NaBH₄, and AgSbF₆ or CF₃COOAg in the mixed solvent of methanol-trichloromethane-toluene under solvothermal conditions, respectively. Driven by SbF₆⁻ and CF₃COO⁻ with different coordination properties, the structural unit [Ag₉(TC4A)(^tBuCC)₄]⁺ in both the compounds migrated in different modes, accompanied by distinct Ag⋯Ag distances. Ag₉ and Ag₁₈ exhibit similar UV-Vis absorption and diffuse reflection spectra along with contrary tendency between photocurrent responses and solid-state fluorescence. The solution stability of Ag₉ and Ag₁₈ was demonstrated by ¹H NMR and MALDI-TOF mass spectrometry. The fluorescence responses of Ag₉ and Ag₁₈ towards different organic molecules were also investigated, which indicated that the polarity of solvent has a certain effect on the emission intensities of Ag₉ and Ag₁₈. This study provides a positive guide for the controlled synthesis and further study of the structure–activity relationship of thiacalix[4]arene-protected silver alkynyl nanoclusters.