Crystal structure of 2-methyl-1H-imidazol-3-ium 3,5-di-carb-oxy-benzoate

The structure of the title salt, C4H7N2 +·C9H5O6 - (1), is reported. The compound is built from a protonated 2-methyl-imidazole and a singly deprotonated trimesic acid. Detailed analysis of bond distances and angles for both ions reveals subtle differences compared with their neutral mol-ecule counterpart. Analysis of the crystal packing in compound 1 reveals the formation of undulating chains by the ions through hydrogen bonding. The chains stack along the b axis through π-π inter-actions and inter-connect with other chains in an out-of-phase arrangement along the ac plane through further hydrogen-bonding inter-actions.

Temperature-induced pseudopolymorphism of molecular salts from a pyridyl bis-urea macrocycle and naphthalene-1,5-disulfonic acid

Molecular salts, often observed as cocrystals, play an important role in the fields of pharmaceutics and materials science, where salt formation is used to tune the properties of active pharmaceutical ingredients (APIs) and improve the stability of solid-state materials. Salt formation via a proton-transfer reaction typically alters hydrogen-bonding motifs and influences supramolecular assembly patterns. We report here the molecular salts formed by the pyridyl bis-urea macrocycle 3,5,13,15,21,22-hexaazatricyclo[15.3.1.1^7,11]docosa-1(21),7(22),8,10,17,19-hexaene-4,14-dione, (1), and naphthalene-1,5-disulfonic acid (H₂NDS) as two salt cocrystal solvates, namely 4,14-dioxo-3,5,13,15,21,22-hexaazatricyclo[15.3.1.1^7,11]docosa-1(21),7(22),8,10,17,19-hexaene-21,22-diium naphthalene-1,5-disulfonate dimethyl sulfoxide disolvate, C₁₆H₂₀N₆O₂²⁺·C₁₀H₆O₆S₂^2-·2C₂H₆OS, (2), and the corresponding monosolvate, C₁₆H₂₀N₆O₂²⁺·C₁₀H₆O₆S₂^2-·C₂H₆OS, (3). This follows the ΔpK_a rule such that there is a proton transfer from H₂NDS to (1), forming the reported molecular salts through hydrogen bonding. Prior to salt formation, (1) is relatively planar and assembles into columnar structures. The salt cocrystal solvates were obtained upon slow cooling of dimethyl sulfoxide-acetonitrile solutions of the molecular components from two temperatures (363 and 393 K). The proton transfer to (1) significantly alters the conformation of the macrocycle, changing the formerly planar macrocycle into a step-shaped conformation with trans-cis urea groups in (2) or into a bowl-shape conformation with trans-trans urea groups in (3).

Three ZnII Coordination Polymers Based on 1,2-Naphthalenedicarboxylate and Different 4,4′-Bipyridyl-like Bridging Co-ligands: Structural Regulation and Properties

Three new ZnII coordination polymers, namely [Zn(ndc)]n (1), {[Zn(ndc)(bpe)]·1.25H2O}n (2), and {[Zn(ndc)(bpee)]·1.25H2O}n (3), were prepared based on in situ reaction of 1,2-naphthalenedicarboxylic anhydride (ndca) with two different 4,4′-bipyridyl-like bridging co-ligands, bpe and bpee (ndc = 1,2-naphthalenedicarboxylate, bpe = 1,2-bis(4-pyridyl)ethane, and bpee = trans-1,2-bis(4-pyridyl)ethylene). In 1, the ZnII and ndc ligands are directly involved in the polymeric frameworks, forming a 2D (43.63) layered network. Complexes 2 and 3 similarly consist of Zn2(ndc)2 binuclear units that are linked by bpe and bpee ligands, respectively, into a 2D (44.62) sheet. However, further analysis indicates that 2 and 3 feature the similar 2-fold interpenetrating structure linked via hydrogen bonding interactions for 2 and aromatic stacking interactions for 3. In addition, the resultant 2D→3D supramolecular frameworks of 2 and 3 are both constructed via aromatic stacking interactions. Also, the fluorescent and thermal properties of the complexes were investigated.

Hydrogen-bonding patterns in a series of multi-component molecular solids formed by 2,3,5,6-tetramethylpyrazine with selected carboxylic acids

Hydrogen-bonding patterns in a series of cocrystals of 2,3,5,6-tetramethylpyrazine with selected carboxylic acids are discussed.