Benzoic acid–3,4-bis­[(pyridin-3-ylmeth­yl)amino]­cyclo­but-3-ene-1,2-dione (1/2)

In the title co-crystal, C16H14N4O2·2C7H6O2, the 3,4-bis­[(pyridin-3-ylmeth­yl)amino]­cyclo­but-3-ene-1,2-dione squareamide mol­ecules assemble into chains along the b axis via N—H⋯O hydrogen bonds. The benzoic acid mol­ecules then hydrogen bond to the pyridine rings via O—H⋯N hydrogen bonds, supported by weaker C—H⋯O hydrogen bonds, forming extended ribbons. The asymmetric unit consists of a half squareamide mol­ecule, sitting on a special position around a twofold axis, and one benzoic acid mol­ecule on a general position

Chiral carboxylic acids and their effects on melting-point behaviour in co-crystals with isonicotinamide

The crystal structures of co-crystals of two systems of chiral carboxylic acids, optically active and racemic 2-phenylpropionic acid and 2-phenylbutyric acid, with isonicotinamide are reported to investigate the effects of the chirality of the chiral carboxylic acids on the melting point of the co-crystal complexes. It was found that the racemic co-crystal has a higher melting point than the optically active co-crystal, which correlates with the denser packing arrangement inherent in centrosymmetric space groups

Structure determination of fatty acid ester biofuels via in situ cryocrystallisation and single crystal X-ray diffraction

Please read abstract in the article.The Claude Leon Foundation and NRF Green Economy Fund (Grant UID: 98053) for financial assistance. They would also like to acknowledge the NRF (Grant UID: 78572) for the purchase of the D8 VENTURE and OHCD device.http://www.rsc.org/journals-books-databases/about-journals/crystengcomm2020-01-07hj2019Chemistr

Polymorphic Co-crystals from Polymorphic Co-crystal Formers: Competition between Carboxylic Acid···Pyridine and Phenol···Pyridine Hydrogen Bonds

The recent literature has shown an increase in the number of co-crystals reported to be polymorphic, with at least 45 such systems identified thus far. The question of whether co-crystals, defined as any multicomponent neutral molecular complex that forms a crystalline solid, are inherently less prone to polymorphism than the individual components is shown to be untrue in four sets of polymorphic co-crystals. The co-crystal formers in this study, acridine, nicotinamide, 3-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, malonic acid, and pimelic acid, are all polymorphic in their unimolecular states and are shown to be dimorphic in the following combinations: (3-hydroxybenzoic acid)·(acridine) [<b>1­(I)</b> and <b>1­(II)</b>], (2,4-dihydroxybenzoic acid)·(nicotinamide) [<b>4­(I)</b> and <b>4­(II)</b>], (malonic acid)·(nicotinamide) [<b>5­(I)</b> and <b>5­(II)</b>], and (pimelic acid)·(nicotinamide) [<b>6­(I)</b> and <b>6­(II)</b>]. These co-crystals are assembled primarily using carboxylic acid and phenol hydrogen bond donors that hydrogen bond to pyridine N or amide carbonyl acceptors. Two different combinations of donors and acceptors are primarily responsible for the formation of polymorphs in <b>1</b> and <b>4</b>, whereas conformational differences within the malonic and pimelic acid molecules lead to different packing arrangements using the same combination of hydrogen bonded interactions in <b>5</b> and <b>6</b>. The 1:2 co-crystal of (3-hydroxybenzoic acid)·(acridine)₂ (<b>2</b>) displays both the phenol O–H···N hydrogen bond observed in <b>1­(I)</b> and the carboxylic acid O–H···N hydrogen bond observed in <b>1­(II)</b>. In addition, a methanol solvate of (2,4-dihydroxybenzoic acid)·(nicotinamide) (<b>3</b>) is reported. DFT calculations show that the carboxylic acid···pyridine hydrogen bond is strongest and one of co-crystallization’s most useful interactions

Pharmaceutical co-crystals with isonicotinamide – vitamin B3, clofibric acid, and diclofenac – and two isonicotinamide hydrates

The co-crystals of three industrially important pharmaceuticalmolecules, the Vitamin B group member nicotinamide (1), the antihyperlipidemic drug clofibric acid (2), and the nonsteroidal anti-inflammatory drug diclofenac (3), are synthesizedwith the co-crystal former isonicotinamide and characterized by thermal analysis and single crystalX-ray diffraction. Two dimorphic hydrates of isonicotinamide were obtained during the course of these experiments: hydrate 4 (formI) has been reported recently, and hydrate 5 (form II) is new. Both are monohydrates but differ in the number of independent molecules in the asymmetric unit, Z0=2 and 8, respectively. Form II is metastable compared to I and converts to form I in the solid state. In all three pharmaceutical co-crystals, it is the pyridine N atom of either the nicotinamide molecule in 1 or the N atom of the isonicotinamide molecule in 2 and 3 that is used in connecting the differentmolecules together, as a hydrogen bond acceptor from the amine of the isonicotinamide in 1 and the carboxylic acid protons in 2 and 3. The carboxylic acid 3 3 3 pyridine hydrogen bond is an often used supramolecular synthon.Asurvey of relevant structures in the Cambridge Structural Database of isonicotinamide and nicotinamide co-crystals is given for completeness, and the co-crystal former ability of isonicotinamide and nicotinamide was investigated by performing density functional theory calculations