Molecular Cage and 1-D Coordination Architectures Assembled from Silver(I) and Dithioether Ligands with Bulky Anthrene Spacers:  Syntheses, Crystal Structures, and Emission Properties

A series of dithioether ligands with bulky anthrene spacers, 9,10-bis[(ethylthio)methyl]anthracene (L), 9,10-bis[(n-propylthio)methyl]anthracene (L), 9,10-bis[(n-butylthio)methyl]anthracene (L), and 9,10-bis[(tert-butylthio)methyl]anthracene (L), have been designed and synthesized. The reactions of these ligands with AgX (X = NO₃^-, ClO₄^-, PF₆^-) lead to the formation of six new metal−organic coordination architectures, [Ag₄(L¹)₂(NO₃)₄](CHCl₃)₂ (1), [Ag₄(L²)₂(NO₃)₄](CHCl₃)₂ (2), [Ag₄(L³)₂(NO₃)₄] (3), {[AgL²(CH₃CN)](ClO₄)}_∞ (4), {[AgL⁴(NO₃)]₂(CH₃CN)}_∞ (5), and {[AgL⁴](PF₆)}_∞ (6), which have been characterized by elemental analyses, IR spectroscopy, and X-ray crystallography. Single-crystal X-ray analyses show that complexes 1−3 possess novel tetranuclear molecular cage structures, while 4−6 have chain structures. In 1−3, the S atoms of the ligands take a μ₂-S bridging coordination mode to link Ag^I ions; thus four S atoms of two ligands link four Ag^I ions to form a tetranuclear cage. The differences of ligand terminal groups in L¹, L², and L³ do not greatly influence the structures of their complexes. However, the changes of the terminal groups cause subtle differences in the coordination geometry of the Ag^I centers, the number of solvent molecules encapsulated in the space among adjacent tetranuclear moieties, and the packing mode of the tetranuclear units. Complex 5, whose ligand bears larger tert-butyl terminal groups, is a one-dimensional (1-D) structure instead of a tetranuclear cage. In addition, the structural differences of 2 and 4 (5 and 6) may contribute to the relatively stronger coordination ability of NO₃^- than that of ClO₄^- (or PF₆^-). These results indicate that the terminal groups of the ligands and the counteranions may play important roles in governing the structural topologies of such metal−organic coordination architectures. Furthermore, complexes 1−6 also display strong blue emissions in the solid state at room temperature.