Supramolecular open-framework architectures based on dicarboxylate H-bond acceptors and polytopic cations with three/four N–H+ donor units

Abstract

Supramolecular assemblages based on anionic H-acceptors and cationic H-donors have been envisioned to elaborate open frameworks maintained by ionic H-bonds. Combinations of di-anionic chloranilate (CA²⁻), oxalate (Ox²⁻), or terephthalate (BDC²⁻) and trisimidazolium or tetrapyridinium derivatives (three and four N–H⁺ donors, respectively) yielded five architectures of formulae [{(H₃TrIB)(CA)_1.5}·2DMF·2.5H₂O] (1), [{(H₄Tetrapy)(CA)₂}·3DMF] (2), [{(H₃TrIB)(HOx)(Ox)}·5H₂O] (3), [{(H₄Tetrapy)(Ox)₂}·5H₂O] (4), and [{(H₄Tetrapy)(BDC)₂(H₂O)}·1DMF·3H₂O] (5) (with TrIB = 1,3,5-trisimidazolylbenzene and Tetrapy = tetrakis[(pyridine-4-yloxy)methyl]methane). Four of these, i.e.1, 2, 4 and 5, show an open framework. Their assembling patterns and framework dimensionalities are mainly governed by the chemical features of the cation. 1D (3) and 2D (1) networks are found with [H₃TrIB]³⁺, whereas 3D diamond-type networks (2, 4, 5) are systematically formed with [H₄Tetrapy]⁴⁺. While the individual adamantanoid cages exhibit large voids in all 3D structures, net catenations (with a total degree of interpenetration up to 19) reduce the potential porosities of the solids to 17–32%. The largest solvent accessible void (42%) is found for the 2D supramolecular organization of 1, for which net interpenetration does not take place. Crystal structures for all five architectures are reported. Framework robustness upon guest departure and gas sorption properties have been explored for materials 1 and 2 with the highest potential accessible voids.