Driving the Assembling of Zirconium Tetraoxalate Metallotectons and Benzimidazolium Cations: From Three Dimensional Hydrogen-Bonded Compact Architectures to Open-Frameworks

Charge-assisted H-bond associations between [Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]<sup>4−</sup> preformed anionic complexes and several ditopic monocations based on the benzimidazolium motif ([H<sub>2</sub>-Bim]<sup>+</sup> cations) have been envisioned for the tentative elaboration of 3D H-bonded and open-framework architectures. Reactions involving [Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]<sup>4−</sup> units and [H<sub>2</sub>-Bim]<sup>+</sup> cations in (a) a charge stoichiometric amount, (b) a defect, and (c) an excess of cation afforded three different compounds of formula {(H<sub>2</sub>-Bim)<sub>4</sub>[Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]}·H<sub>2</sub>O (<b>1</b>), {K(H<sub>2</sub>O)(H<sub>2</sub>-Bim)<sub>3</sub>[Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]}·2H<sub>2</sub>O (<b>2</b>), and {(H<sub>2</sub>-Bim)<sub>4</sub>[Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]} (<b>3</b>), respectively. Structural analyses revealed marked differences in their formulations and in their supramolecular connectivities. These results traduce the importance of cation concentration on the association schemes. Among them, compound <b>3</b> exhibits a chiral structure analyzed as resulting from the interpenetration of two 3D H-bonded homochiral and independent networks. To avoid this interpenetration and to study the influence of the cation substitution for fixed experimental parameters, 2-amino and 2-methyl substituted [H<sub>2</sub>-Bim]<sup>+</sup> cations ([H<sub>2</sub>-2-NH<sub>2</sub>Bim]<sup>+</sup> and [H<sub>2</sub>-2-MeBim]<sup>+</sup>, respectively) have been envisioned as cationic building-blocks. Structure analysis for the corresponding materials ({(H<sub>2</sub>-2-NH<sub>2</sub>Bim)<sub>4</sub>[Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]} (<b>4</b>) and {(H<sub>2</sub>-2-MeBim)<sub>4</sub>[Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]}·7H<sub>2</sub>O (<b>5</b>), respectively) revealed that the amino group contributes in the H-bonded framework, whereas the methyl impairs the formation of H-bonds between the cations and the anions. These observations contribute to explain the marked structural differences between <b>3</b> and these two networks. With 5-methyl- and 5-chlorobenzimidazolium cations ([H<sub>2</sub>-5-MeBim]<sup>+</sup> and [H<sub>2</sub>-5-ClBim]<sup>+</sup>, respectively), [Zr(C<sub>2</sub>O<sub>4</sub>)<sub>4</sub>]<sup>4−</sup> is converted into its binuclear version, [Zr<sub>2</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>7</sub>]<sup>6−</sup>, yielding {(H<sub>2</sub>-5-MeBim)<sub>6</sub>[Zr<sub>2</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>7</sub>]}·3H<sub>2</sub>O (<b>6</b>) with a close-packed 3D-network and {(H<sub>2</sub>-5-ClBim)<sub>6</sub>[Zr<sub>2</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>7</sub>]}·13.5H<sub>2</sub>O (<b>7</b>) with an open-framework architecture (potential solvent accessible void volume of 23%). For <b>7</b>, Cl···π interactions contribute to the cohesion of the 3D supramolecular architecture.