Stoichiometric variation in organic cocrystals, their synthesis, structure elucidation and properties are discussed. Accountable reasons for the occurrence of such cocrystals are emphasised.

The covalent organic polymer synthesis is an elegant way to design materials with various topologies and explore new structures and properties. Herein, we report the synthesis of a novel porous polymer framework with the [3 + 2] structure motif via the condensation of 1,3,5-benzenetricarbonyl trichloride and p-phenylenediamine. The resulting highly stable mesoporous 2D framework material exhibits continuous conjugation of π-electronic system. Apart from gas adsorption properties, this material shows remarkable catalytic activity manifested by the conjugated π-cloud and amide functionality in selective oxidation reactions. Utmost selectivity of the reaction that exclusively yields aldehydes from benzyl alcohols via a free radical pathway is proposed and demonstrated. This is one of the rare cases of any organic polymer material acting as an outstanding organic catalyst with no metal add-ons.

Identification of all possible polymorphs for a pharmaceutical compound is vital for the better formulation of medicine with desired properties. This study demonstrates the application of a mechanochemical approach to reveal new polymorphs of a drug and the potential of variable amounts of solvent in liquid-assisted grinding for solid form screening. Without solvent and by varying the amount of solvent added, we found two new polymorphs and an amorphous form, which were not reported previously. The finding portrays the advantage of the mechanochemical approach as a means of the polymorph screening strategy. While the focus here was on praziquantel, a similar approach is applicable to other pharmaceutical systems. This study also contributed to reinvestigate the solid-state behavior of the chiral praziquantel system, including the melt phase diagram and the role of experimental conditions on its phase behavior.

Three simple bisamide derivatives (G1, G2 and G3) with different structural modifications were synthesized with easy synthetic procedures in order to test their gel behaviour. The outcomes showed that hydrogen bonding was essential in gel formation; for this reason, only G1 provided satisfactory gels. The presence of methoxy groups in G2 and the alkyl chains in G3 hindered the hydrogen bonding between N-H and C=O that occurred G1. In addition, G1 provided thermally and mechanical stable gels, as confirmed with T_sol and rheology experiments. The gels of G1 were also responsive under pH stimuli and were employed as a vehicle for drug crystallization, causing a change in polymorphism in the presence of flufenamic acid and therefore providing the most thermodynamically stable form III compared with metastable form IV obtained from solution crystallization.

FmocFF (9-fluorenyl methoxycarbonyl-phenylalanine) is an extensively studied low-molecular-weight hydrogel. Although there have been numerous studies on FmocFF hydrogel, its potential to form organogels has not been well explored. In this work, we systematically explore the organogels of FmocFF in a wide range of organic solvents. FmocFF is found to be a robust organogeltor, and the subsequent organogels exhibit diverse gelmorphic behavior exhibiting various degrees of crystallinity and morphology depending on the solvent used. The mechanical strength of the organogels is evaluated using rheology. A novel technique, in situ SHG microscopy, is introduced to study the gel structure in its native state. In addition to the solvent–solute interactions that are typically used to predict gelmorphic behavior, we observed indications that the degree of crystallinity also plays a significant role in determining the mechanical properties and structure of FmocFF organogels.

FmocFF is a highly versatile gelator whose π–π-stacking fluorenyl group and hydrogen-bonded peptide backbone permit gelation in a wide spectrum of solvents, providing a rich scaffold for crystal engineering. This study explores the synergistic effects of FmocFF organogels and solvent selection on controlling the polymorphic outcomes of nilutamide, a nonsteroidal antiandrogen drug with complex polymorphism. By systematically varying process parameters such as solvent type and concentration, we demonstrate remarkable control over crystal nucleation and growth pathways. Most significantly, we report the first ambient-temperature isolation of pure nilutamide Form II through acetonitrile-based FmocFF organogel, highlighting the unique interplay between solvent properties and gel fiber networks. Thermal analysis reveals that the organogel not only selectively templates Form II but also affects its thermal pathway. We also present compelling evidence for a new polymorph exhibiting second-harmonic generation (SHG) activity. This would represent the first non-centrosymmetric nilutamide form discovered, suggesting the gel matrix induces symmetry breaking during crystallization. We also characterize a previously unreported nilutamide–chloroform solvate through multiple analytical techniques including PXRD, DSC, FTIR, SXRD, and SHG microscopy. Our findings demonstrate that solvent-specific molecular recognition within gel matrices enables access to entirely new regions of polymorphic space, establishing gel-mediated crystallization as a broadly applicable platform technology for pharmaceutical solid form discovery under mild conditions.