Application of Systematic Search Methods to Studies of the Structures of Urea−Dihydroxy Benzene Cocrystals

Abstract

A systematic search method that identifies trial crystal structures by manipulating a molecular model in directspace within a defined unit cell and comparing calculated and experimental powder X-ray data and assessing calculated lattice energies has been extended to allow simulation of crystal structures having two symmetryindependent molecules within the unit cell. Overall, the methodology developed is composed of three components: first, identification of all isolated molecular-adducts that are viable in terms of intermolecular pair energy calculated using an atom-atom approach; second, clustering of all similar adducts through energy minimization and ranking of the predicted structures; third, treatment of the best molecule-pair adducts identified in a systematic search of all possible intermolecular packing arrangements. The validity of the approach is demonstrated via its application to predict the crystal structures of cocrystals of urea with the isomers of dihydroxy benzene (catechol, resorcinol, and hydroquinone).

Nucleation mechanism and kinetics from the analysis of polythermal crystallisation data: methyl stearate from kerosene solutions

“…This is the case for many industrial materials such as fuels, confectionery products, pharmaceuticals and fine chemicals. In this regard, the shape of the particle needs further quantification, in a manner which draws down on the now comparatively routine application of the molecular modelling of dimers [32,33] , clusters [34][35][36][37][38] , surfaces [30,39,40] , point defects and additives [41][42][43][44][45] action on crystallisation. Such molecular scale modelling can be expected to have an impact e.g.…”

Structural Study of Polymorphs and Solvates of Finasteride

“…11 Nevertheless, NMR is at its most powerful when used in combination with diffraction methods, particularly in view of the development of new techniques within the diffraction manifold (especially for powder diffraction, 12 which can be reinforced by combination with solid-state NMR information). [13][14][15][16] The present paper uses CPMAS NMR, X-ray diffraction and thermal methods to examine a number of polymorphs and solvates of the aza-steroid finasteride (1), 17-b-(N-t-butyl carbamoyl)-4-aza-5-a-androst-1-ene-3-one. …”

Remarkable dielectric properties of 1 : 2 inter-molecular compound of 2-(4-(dimethylamino) benzylideneamino) benzoic acid and urea due to excited-state intramolecular proton transfer

“…It has a bifunctional hydrogen bond donor and acceptor (-NH 2 and O]C) and 2-(4-(dimethylamino) benzylideneamino) benzoic acid (DMABAB) exists as a zwitterion. Therefore, these compounds were selected to study their eutectics and inter-molecular compounds.…”

“…2 The exploitation of non-covalent interactions (hydrogen bonding, dipole-dipole interactions, induced dipole interactions, van der Waal interaction, etc.) between molecules coupled with molecular packing patterns can result in many desirable electrical, magnetic, optical and dielectric properties in materials of commercial and technological importance.…”