Faculté des sciences

Counterion effect on the formation of coordination polymer networks between AgNO₃ and L (2,2′-oxybis(ethane-2,1-diyl) diisonicotinate) Part 2

Sague, Jorge L. ; Meuwly, Markus ; Fromm, Katharina M.

In: CrystEngComm, 2008, vol. 10, p. 1542-1549

Herein we report the synthesis and characterization by single crystal X-ray diffraction of three new silver(I) complexes {[Ag₂·L₂](NO₃)₂(H₂O)₄} (1), {[Ag₂·L₂](NO₃)₂} (2) and {[Ag₂·L₂](NO₃)₂} (3). Whereas compounds 2 and 3 are... More

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    Summary
    Herein we report the synthesis and characterization by single crystal X-ray diffraction of three new silver(I) complexes {[Ag₂·L₂](NO₃)₂(H₂O)₄} (1), {[Ag₂·L₂](NO₃)₂} (2) and {[Ag₂·L₂](NO₃)₂} (3). Whereas compounds 2 and 3 are polymorphs, compound 1 crystallizes as the pseudo-polymorphic form of 2 and 3. These compounds were obtained from the reaction of silver nitrate with the flexible ligand 2,2′-oxybis(ethane-2,1-diyl) diisonicotinate (L). The main structural motifs for complexes 1–3 are zero-dimensional metallacycles, in which two silver(I) cations are coordinated by two ligands L and their counterions. As a result of its unpredictable coordinating ability, the nitrate anion coordinates the Ag(I) cation in a μ¹μ²-fashion in complex 1, in 2 it is coordinated in an asymmetrical μ²-mode, and in 3 the anion is strongly μ²-symmetrical coordinating. The coordination of the NO₃⁻ counterions to the metal cation affects the overall supramolecular interactions in the crystalline state of the complexes (e.g. Ag(I)⋯Ag(I), π⋯π, hydrogen bonds and C–H⋯π interactions). These interactions determine the physical properties of these compounds. On heating, the crystals of compound 3 are irreversibly transformed into compound 2. The conversion is supported by the change in the coordination mode of the nitrate counterion toward the Ag(I) cation. The solubility dependence of AgNO₃ in the different organic solvents used for the reactions may determine the structural diversity in the supramolecular architecture for these complexes.