Themed collection Polymorphism
Welcome to this CrystEngComm themed issue on Polymorphism.
Ostwald's rule and enantiotropy: polymorph appearance in the crystallisation of p-aminobenzoic acid
The development of rational crystallisation strategies in polymorphic systems requires the experimental manipulation of both kinetics and thermodynamics.
Concomitant polymorphs of p-iso-propylcalixarene
Sublimation of p-iso-propylcalixarene (form IP) under reduced pressure results in the concomitant formation of two new polymorphs (forms IIP and IIIP).
Solid state structures of p-cresol revisited
Detailed analysis of the two polymorphic solid state forms of p-cresol are presented and possible transformation of the two forms are proposed.
How focussing on hydrogen bonding interactions in amino acids can miss the bigger picture: a high-pressure neutron powder diffraction study of ε-glycine
Analysis of intermolecular interactions using purely geometric criteria can be misleading: glycine exhibits apparently ideal H-bonding geometry for dimers with repulsive interaction energies.
Isomorphous three-component crystals (pseudopolymorphs of binary cocrystals) based on lattice inclusion of guests with a sterically-rigidified tetraarylpyrene host
Pseudopolymorphs of binary cocrystals of the host and cyclododecene constitute ternary cocrystals.
Crystallization and characterization of cocrystals of piroxicam and 2,5-dihydroxybenzoic acid
Two cocrystals of piroxicam (PRX) and 2,5-dihydroxybenzoic acid (HBA) were found using a microfluidic cocrystal screening approach; one crystal contained an acetone (ACT) impurity.
Structural insights into the hexamorphic system of an isoniazid derivative
The compound isonicotinic acid (E)-(1-phenylethylidene)hydrazide exists in 6 different structural forms isolated through complex manipulations on a Kofler hot stage.
In situ Raman mapping for identifying transient solid forms
In situ Raman surface mapping on a trihydrate sample provides evidence for the existence of a transient phase X on the route to its stable anhydrous polymorph I. The phase transformation events are observed in the order trihydrate → transient phase → form I.
N–H⋯π induced configurational isomerism and the role of temperature in the Z to E isomerization of 2-fluoro-N′-(3-fluorophenyl)benzimidamide
The role of temperature in polymorphism and the isolation of configurational isomers of 2-fluoro-N′-(3-fluorophenyl)benzimidamide have been investigated.
Isotopomeric polymorphism in a “doubly-polymorphic” multi-component molecular crystal
Isotopomeric polymorphism is observed in complexes of isonicotinamide with oxalic acid, highly unusual here in that each isotopic complex is itself polymorphic, a situation of “double polymorphism”. The four polymorphic forms exhibit different degrees of hydron transfer.
Static and lattice vibrational energy differences between polymorphs
Lattice energy, entropy and free energy differences for over 500 pairs of known polymorphs are computed and discussed.
Crystallization and disorder of the polytypic α1 and α2 polymorphs of piroxicam
The polytypic α1 and α2 polymorphs of piroxicam are described and it is shown that they can be crystallized controllably.
Polymorphism in anti-hyperammonemic agent N-carbamoyl-L-glutamic acid
Solid form screen of anti-hyperammonemic drug carglumic acid (CGA) resulted in two polymorphs, Form-I and Form-II. The crystal structure of Form-I is sustained by an acid catemer synthon, whereas Form-II has an acid–amide heterosynthon. Slurry grinding, thermal stress, stability measurements, and DVS analysis confirm the thermodynamic stability of Form-I.
The reluctant polymorph: investigation into the effect of self-association on the solvent mediated phase transformation and nucleation of theophylline
Evidence that theophylline forms aggregates in H-bond donor solvents, and the presence of these aggregates hinders the nucleation and phase transformation to form IV.
Virtual hydrate screening and coformer selection for improved relative humidity stability
The descriptors were determined, which can be most efficiently applied to virtual screening in order to provide answers to the following questions: 1) what is the propensity to form a solid state hydrate of a pharmaceutical compound, and 2) which coformer would provide for the highest stability with respect to relative humidity conditions?
Two polymorphs of 4-hydroxypiperidine with different NH configurations
4-Hydroxypiperidine 1 exists in two crystal forms, tetragonal 1t with axial NH and orthorhombic 1o with equatorial NH.
Ultra-wideline 14N solid-state NMR as a method for differentiating polymorphs: glycine as a case study
14N solid-state NMR is useful for differentiating polymorphs and chemically distinct nitrogen-containing compounds. A case study of glycine is presented.
Solid-state identity of 2-hydroxynicotinic acid and its polymorphism
The solid-state identity of 2-hydroxynicotinic acid is unveiled to be its tautomer, 2-oxo-1,2-dihydro-3-pyridinecarboxylic acid (2-ODHPCA), by both experimental and computational means. Four distinctive crystal structures are discovered of the compound.
Isostructurality and the conformational role of the 2′,3′-moieties in the diversity of lamivudine crystal forms probed in halide salts
The robustness of supramolecular synthons in two lamivudine salts with hydrobromic and hydrofluoric acids and the role of the five-membered ring conformation in the assembly of a polymorph of lamivudine hydrochloride.
On molecular complexes derived from amino acids and nicotinamides in combination with boronic acids
Cocrystals of boronic acids in combination with L-proline, nicotinamide and isonicotinamide have been structurally characterized.
About this collection
Guest Edited by Professors T.N. Guru Row (Indian Institute of Science, Bangalore) and Ashwini Nangia (University of Hyderabad), this issue focuses on the contemporary theme of polymorphism in all its manifestations and applications. It aims to cover the fundamental understanding of crystal nucleation and growth, energies of polymorphs and their phase transformations, polymorphism in non-ambient conditions, novel polymorphs induced by additives and hetero-nuclei, and polymorphs resulting from spatial confinement.