Modular metallotecton for engineering permanently porous frameworks: supernumerary role of ancillary ion

Abstract

The formation of robust supramolecular frameworks built from hetero-polytopic metal complexes and interacting with different ancillary ions remains a long-standing and underexplored desire. Herein, the secondary sphere interaction chemistry of [Ru(5-oxido-6-hydroxy-1,10-phenanthroline)_a(5,6-dihydroxy-1,10-phenanthroline)_(3−a)]^−(a−2) (1) (a = 1, 3) coordination ion is reported, where the π-conjugated phenanthroline ligands are functionalized with catecholate groups used as H-bond donors and ligands. The deprotonation of the catechols is found to control the overall charge stoichiometry in 1, acting as a metallotecton to interact with anions of different basicity (Cl⁻ in 1.Cl and Br⁻ in 1.Br) as well as with Li⁺ cations (in 1.Li⁺). These interactions lead to the formation of 2D porous honeycomb networks without any significant alteration in the molecular packing. This implies that the self-assembly process is controlled by complementary intermolecular non-covalent interactions making the choice of the ancillary ion insignificant. The robust porous structure of the frameworks is established by uptake of D₂O and I₂ molecules within the microporous channels. This work demonstrates that supramolecular frameworks appear as flexible candidates for applications in gas sorption, separation and chemical sensing.