Two Faces of Water in the Formation and Stabilization of Multicomponent Crystals of Zwitterionic Drug-Like Compounds (original) (raw)
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Acta crystallographica Section B, Structural science, crystal engineering and materials, 2017
Single-crystal X-ray diffraction and quantum mechanical theories were used to examine in detail the subtle nature of non-covalent interactions in the [2:1:1] multicomponent crystal of 1,1-aminocyclopentanecarboxylic acid:oxalic acid:water. The crystal, which is a hydrate salt of the amino acid with the hydrogen-oxalate ion, also contains the zwitterion of the amino acid in equal proportions. It was found that a dimeric cation [Acc5(Z)...Acc5(C)](+) bonded by an O-H...O hydrogen bond exists due to a charge transfer between acid and carboxylate groups. The three-dimensional crystal is built by blocks stacked along the [101] direction by dispersion interactions, with each block growing along two directions: a hydrogen oxalate HOX(-)...HOX(-) catameric supramolecular structure along the [010] direction; and double ...HOX(-)-W-[Acc5(Z)... Acc5(C)](+)... chains related by inversion centers along the [1 0 {\bar 1}] direction. A PBE-DFT optimization, under periodic boundary conditions, was ...
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Synthesis of multicomponent solid forms is an important method of modifying and fine-tuning the most critical physicochemical properties of drug compounds. The design of new multicomponent pharmaceutical materials requires reliable information about the supramolecular arrangement of molecules and detailed description of the intermolecular interactions in the crystal structure. It implies the use of a combination of different experimental and theoretical investigation methods. Organic salts present new challenges for those who develop theoretical approaches describing the structure, spectral properties, and lattice energy Elatt. These crystals consist of closed-shell organic ions interacting through relatively strong hydrogen bonds, which leads to Elatt > 200 kJ/mol. Some technical problems that a user of periodic (solid-state) density functional theory (DFT) programs encounters when calculating the properties of these crystals still remain unsolved, for example, the influence of ...
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2019
Cocrystal monohydrate of nitrofurantoin (NF) with melamine (MELA) has been studied as NF is an antibacterial drug used for the treatment of urinary tract infections. The structure of nitrofurantoin-melamine-monohydrate (NF-MELA-H 2 O) is characterized by FT-IR and FT-Raman spectroscopy. The energies and vibrational frequencies of the optimized structures calculated using quantum chemical calculations. Supported by normal coordinate analyses and potential energy distributions (PEDs), the complete vibrational assignments recommended for the observed fundamentals of cocrystal hydrate. With the aim of inclusion of all the H-bond interactions, dimer of NF-MELA-H 2 O has been studied as only two molecules of cocrystal hydrate are present in the unit cell. By the study of dimeric model consistent assignment of the FT-IR and FT-Raman spectrum obtained. H-bonds are of essential importance in an extensive range of molecular sciences. The vibrational analyses depicts existence of H-bonding (O-HN) between water O-H and pyridyl N atom of MELA in both monomer and dimer. To probe the strength and nature of H-bonding in monomer and dimer, topological parameters such as electron density (ρ BCP), Laplacian of electron density (2 ρ BCP), total electron energy density (H BCP) and H-bond energy (E HB) at bond critical points (BCP) are evaluated by quantum theory of atoms in molecules (QTAIM). Natural bond orbitals (NBOs) analyses is carried out to study especially the intra and intermolecular Hbonding and their second order stabilization energy (E (2)). The value of HOMO-LUMO energy band gap for NF-MELA-H 2 O (monomer and dimer both) is less than NF, showing more chemical reactivity for NF-MELA-H 2 O. Chemical reactivity has been described with the assistance of electronic descriptors. Global electrophilicity index (ω = 7.3992 eV) shows that NF-MELA-H 2 O behaves as a strong electrophile than NF. The local reactivity descriptors analyses such as Fukui functions, local softnesses and electrophilicity indices performed to determine the reactive sites within NF-MELA-H 2 O. In MEP map of NF-MELA
The Journal of Organic Chemistry, 1987
ha-12-crown-4 forms a 2:l sandwich complex similar to that known for 12-crown-4 sodium iodide, except that the presence of >NH in each ring makes Na-donor bonds unequal in strength and leads to hydrogen bonding with the counterion. The heteroatoms of each macroring are coplanar, and both nitrogens are on the same side of the complex (twist angle 43" from eclipsed). This may be due to a long (and weak) hydrogen bond to iodide, an interaction confirmed by analysis using Raman spectroscopy. The previously unreported 1:l and 2:l cation affinity constants (anhydrous MeOH, 25 "C) for this macrocycle are log Kscl:l) = 1.3 f 0.1 and log Kscz:l, = 2.0 k 0.1, respectively.