Synthesis, structure, and characterization of a series of Ag(i), Cu(ii) and Ni(ii) complexes based on 2,5-dimethyl-1,3,4-thiodiazole

Abstract

Using 2,5-dimethyl-1,3,4-thiodiazole (L) as ligand, a series of Ag(I), Cu(II) and Ni(II) complexes, namely, [Ag₄(μ₂-L)₆(H₂O)₂](ClO₄)₄·2H₂O (1), [Ag₄(μ₂-L)₄(μ₂-CF₃CO₂)₂(μ₃-CF₃CO₂)₂] (2), [Ag₂(μ₂-L)₃(CH₃CN)₂](AsF₆)₂ (3), [Ag₂(μ₂-L)₂(μ₂-NO₃)₂]_n (4), [Cu(L)₂(μ₂-NO₃)₂] (5), [Cu(μ₂-L)(μ_1,1-N₃)₃(μ₂-CH₃COO)]_n (6) and [Ni₉(μ₂-L)₆(L)₃(μ₆-CO₃)₂(DMF)₃(H₂O)₆(μ₃-OH)₆]₂[Ni₉(μ₂-L)₆(μ₆-CO₃)₂(H₂O)₁₂(μ₃-OH)₆](ClO₄)₂₄·9H₂O (7) were isolated and their crystal structures determined via single-crystal X-ray diffraction. In 1, six L ligands bridge four neighboring Ag(I) centers forming a tetranuclear cation Ag₄ cluster. While in 2, μ₃-CF₃CO₂⁻ anions bridge two pairs of di-nuclear silver(I) clusters forming another type of tetranuclear neutral Ag₄ cluster. 3 is a dinuclear Ag(I) complex and 4 is a one-dimensional (1D) chain constructed via dinuclear Ag(I) sub-units, in which μ₂-NO₃⁻ groups bridge neighboring di-nuclear Ag(I) clusters into a 1D polymeric chain. When Cu(NO₃)₂ was employed in the reaction system instead of silver(I) salts, a mono-nuclear Cu(II) complex 5 was obtained. When Cu(Ac)₂ and NaN₃ were further introduced in to the reaction system of 5 instead of Cu(NO₃)₂, a 1D copper(II) chain 6 constructed with dinuclear copper(II) units was isolated, in which three different types of bridging (μ_1,1-azido, acetate and L ligands) can be simultaneously observed. It is interesting that when self-assembly of Ni(ClO₄)₂·6H₂O, L, Na₂CO₃, and NaN₃ in the molar ratio of 4 : 2 : 1 : 8 in CH₃OH/DMF/H₂O produced well-shaped green crystals of 7. Structural analysis revealed that 7 contains two types of Ni₉ clusters with an overall Pc1 non-central symmetry. To our knowledge, 7 represents a unique example of M₉L₆ and M₉L₉ cages. The result also reveals that it can be expected that using L ligands as precursors has great potential for constructing these functional materials with intriguing structural motifs such as polynuclear metal clusters. Electrospray ionization mass spectrometry measurements studies for 1–4 demonstrate that in a DMSO solution, complex 1 can still retain the form of a tetranuclear silver(I) cluster. In the solid state, complexes 1–4 exhibit strong fluorescent emission bands, which may be assigned to ligand-to-metal charge transfer. The luminescent properties of these complexes in a DMSO solution varied from blue light to green light at ambient temperature.