Supramolecular Isomerism and Various Chain/Layer Substructures in Silver(I) Compounds: Syntheses, Structures, and Luminescent Properties

A systematic investigation on the Ag/bpy/(H)dpa family represents seven Ag(I) supramolecular compounds with distinct structural features, Ag₂(bpy)_0.5(dpa) (1), Ag₂(bpy)_1.5(dpa)(H₂O) (2), Ag(bpy)_0.5(Hdpa) (3), α-[Ag(bpy)]·(Hdpa) (4), β-[Ag(bpy)]·(Hdpa) (5), [Ag(bpy)]₂·(dpa)·6(H₂O) (6), and [Ag(bpy)]₄·(dpa)·2(NO₃)·6(H₂O) (7) (H₂dpa = 1,1′-biphenyl-2,2′-dicarboxylic acid, bpy = 4,4′-bipyridine). Of particular interest about this work is that supramolecular isomerism is observed between compounds 4 and 5. Single-crystal X-ray structural analysis reveals the structural diversity of the formed products. Compounds 1−5 are extended from various one-dimensional (1D) chain substructures. Three distinct 1D chains exist in 1−3: one 1D chain of {Ag₂(dpa)} exists in compound 1, one supramolecular chain of tetranuclear {Ag₂(dpa)(H₂O)}₂ subunits linked by Ag···Ag interactions (argentophilic interactions) and hydrogen bonding interactions is observed in 2, and one 1D alternate chain of eight-membered {Ag₂(Hdpa)₂} ring bridged by bpy is present in 3. However, two different 1D supramolecular double chains of [Ag(bpy)(Hdpa)] are found in 4 and 5, which are sustained by the combination of weak Ag···O interactions, π−π stacking interactions, and argentophilic interactions in 4 while only by π−π stacking interactions in 5. These 1D chain substructures are further threaded into a 2D covalent layer bridged by bpy (1) or 2D (3 and 4)/3D (2 and 5) supramolecular architectures with the help of supramolecular driving forces in different ways. In contrast to compounds 1−5, compounds 6 and 7 are based upon 2D supramolecular substructures of [Ag(bpy)]₂·(dpa) and {[Ag(bpy)]₄·(dpa)·(H₂O)}_n²ⁿ⁺, respectively. The most striking feature of 6 is that a quasi-1D water aggregate is confined in the 1D channel of the 3D porous interdigitated host framework. Greatly different from compound 6, compound 7 is a nitrate-templated 3D supramolecular framework constructed from a positively charged layer substructure through versatile hydrogen bonds. The diversity of the product structures illustrates that controlled synthesis by adjusting the molar ratio of precursors or the pH value of the solution is a facile and effective approach to further design and construct novel supramolecular assemblies with distinct structural features. Moreover, the thermal dynamic properties and fluorescent properties of all compounds except 1 are also investigated.