The Role of π-Stacking in the Composition of Phloroglucinol and Phenazine Cocrystals

Abstract

Cocrystallization of phloroglucinol (PHG) and phenazine (Phen) afforded cocrystals of 1:1.5, 1:1.75, and 1:2 PHG • Phen stoichiometry upon grinding the two components in different starting ratios and then using suitable solvents for single crystal growth. The phenol • • • pyridine O-H • • • N synthon directs 1:1.5 bimolecular organization of PHG and Phen molecules in a π-stacked motif (cocrystal 1). Additional phenazine molecules insert in the π-stacks to give a higher proportion of the aromatic species in cocrystals 2 and 3 (1:1.75 and 1:2). A hydrate cocrystal of 1:2:1 composition (4) was also obtained. The π-stack dimer motif of phenazine templated by the 1,3-(OH) 2 moiety of phloroglucinol at about van der Waals distance in these crystal structures is postulated to promote the crystallization of the β-phenazine polymorph having a sandwich herringbone motif. These results suggest a role for cocrystal formers as hydrogen bond additives that favor and stabilize specific motifs for the crystallization of new polymorphs.

Stabilization of [BiCl6]3− and [Bi2Cl10]4− with various organic precursors as cations leading to inorganic–organic supramolecular adducts: Syntheses, crystal structures and properties of [C5H7N2]3[BiCl6], [C5H7N2][C5H8N2][BiCl6] and [C10H10N2]2[Bi2Cl10]

“…3. Even though these are weak p-p interactions [23], the compound 1 gives a 2-dimensional supramolecular network due to the existence of further strong C-HCl hydrogen bonds (Fig. 3).…”

Combinatorial Crystal Synthesis: Structural Landscape of Phloroglucinol:1,2‐bis(4‐pyridyl)ethylene and Phloroglucinol:Phenazine

“…We now discuss the phloroglucinol-phenazine system (PGL:PHE). This consists of seven crystal forms, four of which (I, II, III, IV) have been previously reported, [14] and the other three of which (V, VI, VII) are reported herein. These new forms are illustrated in Figure 4.…”

Investigation of Carbohydrates and Their Derivatives as Crystallization Modifiers

“…Pharmaceutical co-crystals have been described for many drugs such as acetaminophen, aspirin, ibuprofen, flurbiprofen, sulfadimidine, etc. (Vishweshwar et al, 2005;Vishweshwar et al, 2006b;Caira, 2007;Rodríguez-Hornedo et al, 2007;Babu et al, 2008;Sarma et al, 2008,). Co-crystals of antitubercular drugs with dicarboxylic acids were reported using carboxylic acid-pyridine synthon as a reliable tool (Vishweshwar et al, 2003).…”