Diazole-based powdered cocrystal featuring a helical hydrogen-bonded network: Structure determination from PXRD, solid-state NMR and computer modeling
authors Sardo, M; Santos, SM; Babaryk, AA; Lopez, C; Alkorta, I; Elguero, J; Claramunt, RM; Mafra, L
nationality International
journal SOLID STATE NUCLEAR MAGNETIC RESONANCE
author keywords Cocrystal; Diazole; NMR Crystallography; Crystal engineering; Hydrogen bond network; C-H center dot center dot center dot pi interactions; Solid-state NMR
keywords CRYSTAL-STRUCTURE PREDICTION; AB-INITIO CALCULATIONS; X-RAY-DIFFRACTION; PI-INTERACTIONS; H-1-NMR SPECTROSCOPY; MAS NMR; AROMATIC NANOCHANNELS; POLARIZATION TRANSFER; QUADRUPLE PROTON; CO-CRYSTALS
abstract We present the structure of a new equimolar 1:1 cocrystal formed by 3,5-d imethy1-1H-pyrazole (dmpz) and 4,5-dimethy1-1H-imidazole (dmim), determined by means of powder X-ray diffraction data combined with solid-state NMR that provided insight into topological details of hydrogen bonding connectivities and weak interactions such as C-H center dot center dot center dot pi contacts. The use of various 1D/2D C-13, N-15 and H-1 high-resolution solid-state NMR techniques provided structural insight on local length scales revealing internuclear proximities and relative orientations between the dmim and dmpz molecular building blocks of the studied cocrystal. Molecular modeling and DFT calculations were also employed to generate meaningful structures. INT refinement was able to decrease the figure of merit R(F-2) from similar to 11% (PXRD only) to 5.4%. An attempt was made to rationalize the role of N-H center dot center dot center dot N and C-H center dot center dot center dot pi contacts in stabilizing the reported cocrystal. For this purpose four imidazole derivatives with distinct placement of methyl substituents were reacted with dmpz to understand the effect of methylation in blocking or enabling certain intermolecular contacts. Only one imidazole derivative (dmim) was able to incorporate into the dmpz trimeric motif thus resulting in a cocrystal, which contains both hydrophobic (methyl groups) and hydrophilic components that self-assemble to form an atypical ID network of helicoiclal hydrogen bonded pattern, featuring structural similarities with alpha-helix arrangements in proteins. The 1:1 dmpz...dmim compound I is the first example of a cocrystal formed by two different azoles. (C) 2014 Elsevier Inc. All rights reserved.
publisher ACADEMIC PRESS INC ELSEVIER SCIENCE
issn 0926-2040
year published 2015
volume 65
beginning page 49
ending page 63
digital object identifier (doi) 10.1016/j.ssnmr.2014.12.005
web of science category Chemistry, Physical; Physics, Atomic, Molecular & Chemical; Physics, Condensed Matter; Spectroscopy
subject category Chemistry; Physics; Spectroscopy
unique article identifier WOS:000350874400007
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