Dihydrofolate Reductase Inhibitors: The Pharmacophore as a Guide for Co-Crystal Screening.

In this work, co-crystal screening was carried out for two important dihydrofolate reductase (DHFR) inhibitors, trimethoprim (TMP) and pyrimethamine (PMA), and for 2,4-diaminopyrimidine (DAP), which is the pharmacophore of these active pharmaceutical ingredients (API). The isomeric pyridinecarboxamides and two xanthines, theophylline (THEO) and caffeine (CAF), were used as co-formers in the same experimental conditions, in order to evaluate the potential for the pharmacophore to be used as a guide in the screening process. In silico co-crystal screening was carried out using BIOVIA COSMOquick and experimental screening was performed by mechanochemistry and supported by (solid + liquid) binary phase diagrams, infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). The in silico prediction of low propensities for DAP, TMP and PMA to co-crystallize with pyridinecarboxamides was confirmed: a successful outcome was only observed for DAP + nicotinamide. Successful synthesis of multicomponent solid forms was achieved for all three target molecules with theophylline, with DAP co-crystals revealing a greater variety of stoichiometries. The crystalline structures of a (1:2) TMP:THEO co-crystal and of a (1:2:1) DAP:THEO:ethyl acetate solvate were solved. This work demonstrated the possible use of the pharmacophore of DHFR inhibitors as a guide for co-crystal screening, recognizing some similar trends in the outcome of association in the solid state and in the molecular aggregation in the co-crystals, characterized by the same supramolecular synthons.

On the Performance of Hybrid Functionals for Non-linear Optical Properties and Electronic Excitations in Chiral Molecular Crystals: The Case of Butterfly-Shaped Dicinnamalacetone.

Purely organic chiral molecular assemblies in the solid state hold great potential for non-linear optical applications. Herein, a newly synthesised molecular system is reported, namely, dicinnamalacetone, an otherwise planar molecule that crystallises in a disordered non-centrosymmetric form with four different conformations having an overall predominance of a particular helicity. A combined experimental and theoretical approach, including single-crystal X-ray diffraction, Kurtz-Perry and ab initio methods, is employed to characterise the system and benchmark the performance of hybrid functionals for the prediction of non-linear optical properties and electronic excitations. Comparison of experiment and theory points to a particular set of hybrid functionals that provides an optimal description of this molecular system.

3-(Ammonio-methyl)-pyridinium bis-(perchlorate).

In the title molecular salt, C6H10N2 (2+)·2ClO4 (-), the Cl-O bond lengths [anion 1: 1.369 (3)-1.415 (3); anion 2: 1.420 (2)-1.441 (2) Å] and the O-Cl-O angles [anion 1: 105.4 (2)-111.8 (4); anion 2: 107.8 (1)-110.3 (1)°] indicate a slight distortion of the perchlorate anions from regular tetra-hedral symmetry. In the crystal, the components are linked into columns along the a-axis direction via N-H⋯O and C-H⋯O hydrogen bonds, with stacks of the organic mol-ecules being surrounded by stacks of perchlorate anions.

Poly[µ2-aqua-µ4-[1-(4-chloro-phen-yl)-4,4,4-tri-fluoro-butane-1,3-dionato]-potassium].

In the title compound, [K(C10H5ClO2F3)(H2O)] n , the two independent K(+) ions are located on a twofold rotation axis. For each of the cations, the distorted cubic coordination environment is defined by two F and four O atoms of symmetry-related 1,4-chloro-phenyl-4,4,4-tri-fluoro-butane-1,3-dionate anions and by two O atoms of water mol-ecules. The µ4-bridging character of the anion and the µ2-bridging of the water mol-ecule lead to the formation of layers parallel to (100). The coordinating water mol-ecules are also involved in O-H⋯O hydrogen bonds that reinforce the mol-ecular cohesion within the layers, which are stacked along [100]. The ß-diketonate anion is not planar, with an angle of 31.78 (10)° between the mean planes of the diketonate group and the chloro-phenyl ring.

4,7-Diphenyl-1,10-phenanthroline methanol hemisolvate.

The asymmetric unit of the title compound, C24H16N2·0.5CH3OH, is comprised of two independent bathophenanthroline mol-ecules (systematic name: 4,7-diphenyl-1,10-phenanthroline) and one methanol mol-ecule. The bathophenanthroline mol-ecules are not planar as there is a considerable rotation of all terminal phenyl rings with respect to the central phenanthroline units [dihedral angles in the range 52.21 (12)-62.14 (10)°]. In addition, a non-negligible torsion is apparent in one of the phenanthroline units: the angle between the mean planes of the two pyridine rings is 14.84 (13)°. The methanol solvent mol-ecule is linked to both N atoms of a bathophenanthroline mol-ecule through a bifurcated O-H⋯(N,N) hydrogen bond.

Amorphous Solid Forms of Ranolazine and Tryptophan and Their Relaxation to Metastable Polymorphs.

Different methods were explored for the amorphization of ranolazine, a sparingly soluble anti-anginal drug, such as mechanochemistry, quench-cooling, and solvent evaporation from solutions. Amorphous phases, with Tg values lower than room temperature, were obtained by cryo-milling and quench-cooling. New forms of ranolazine, named II and III, were identified from the relaxation of the ranolazine amorphous phase produced by cryo-milling, which takes place within several hours after grinding. At room temperature, these metastable polymorphs relax to the lower energy polymorph I, whose crystal structure was solved in this work for the first time. A binary co-amorphous mixture of ranolazine and tryptophan was produced, with three important advantages: higher glass transition temperature, increased kinetic stability preventing relaxation of the amorphous to crystalline phases for at least two months, and improved aqueous solubility. Concomitantly, the thermal behavior of amorphous tryptophan obtained by cryo-milling was studied by DSC. Depending on experimental conditions, it was possible to observe relaxation directly to the lower energy form or by an intermediate metastable crystalline phase and the serendipitous production of the neutral form of this amino acid in the pure solid phase.

Poly[piperazine-1,4-diium [µ(4)-chlorido-µ(3)-chlorido-tri-µ(2)-chlorido-chloridodicadmate(II)] monohydrate].

In the title compound, {(C(5)H(14)N(2))[Cd(2)Cl(6)]·H(2)O}(n), the asymmetric unit contains one piperazinediium cation, one [Cd(2)Cl(6)](2-) anion and a water mol-ecule. The coordination geometries of the two Cd(2+) cations are distorted octa-hedral. Adjacent Cd(II) atoms are inter-connected alternately by paired chloride bridges, generating polymeric chains parallel to [010]. Neighbouring chains are connected by O-H⋯Cl hydrogen bonds involving the water mol-ecules, forming layers at z = n/2. The crystal packing is further stabilized by inter-molecular N-H⋯Cl and N-H⋯O hydrogen bonds, one of which is bifurcated.

5,10,15,20-Tetra-kis(4-acetyl-oxyphen-yl)porphyrin including an unknown solvate.

Mol-ecules of the title compound, C52H38N4O8, are located on an inversion center so that the asymmetric cell contains one half of the mol-ecule. The macrocycle exhibits a ruffled conformation with a maximum deviation of 0.16 Šfor the 24 macrocycle atoms: the dihedral angle between adjacent five-membered rings is 5.13 (19)°. The benzene rings are rotated by 70.25 (19)° with respect to their adjacent protonated five-membered rings, and by 65.56 (19)° with respect to the unprotonated rings. The porphyrin conformation is supported by bifurcated N-H⋯(N,N) hydrogen bonds. The structure contained poorly resolved solvent mol-ecules in voids of volume 217 Å(3) per unit cell. The latter were treated using the SQUEEZE routine in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148-155]. As the solvent could not be identified exactly, it was not included in the calculation of the overall formula weight, density and absorption coefficient.

Monoclinic polymorph of 2-(pyrimidin-2-ylsulfan-yl)acetic acid.

The title compound, C(6)H(6)N(2)O(2)S, is a new polymorphic form of 2-(pyrimidin-2-ylsulfan-yl)acetic acid. Unlike the previous orthorhombic polymorph [Pan & Chen (2009 ▶) Acta Cryst. E65, o652], the mol-ecules are not planar: the aromatic ring makes an angle of 80.67 (17)° with the carboxyl plane. In the crystal, mol-ecules are linked by O-H⋯N hydrogen bonds into chains along [02].

Diaqua-(6-bromo-picolinato-κN,O)(nitrato-κO,O)copper(II).

In the monomeric title complex, [Cu(C(6)H(3)BrNO(2))(NO(3))(H(2)O)(2)], the Cu(II) ion is coordinated by a bidentate 6-bromo-picolinate ion, one nitrate ion and two water mol-ecules in a geometry inter-mediate between five- and six-coordinate. Conventional O-H⋯O hydrogen bonds link the complex mol-ecules, forming layers parallel to the ab plane.

Phenyl-hydrazinium (6-carb-oxy-pyridine-2-carboxyl-ato)(pyridine-2,6-dicarboxyl-ato)cobaltate(II)-pyridine-2,6-dicarb-oxy-lic acid-water (1/1/3).

The asymmetric unit of the title compound, (C(6)H(9)N(2))[Co(C(7)H(3)NO(4))(C(7)H(4)NO(4))]·C(7)H(5)NO(4)·3H(2)O, contains one (6-carb-oxy-pyridine-2-carboxyl-ato)(pyridine-2,6-dicarboxyl-ato)cobaltate(II) anion, one phenyl-hydrazinium cation, one pyridine-2,6-dicarb-oxy-lic acid mol-ecule and three uncoordin-ated water mol-ecules, part of which are disordered. The Co(II) ion is coordinated by a pyridine-2,6-dicarboxyl-ate ion and a 6-carb-oxy-pyridine-2-carboxyl-ate ligand almost perpendicular to each other [the angle between the least-squares planes is 87.38 (4)°] and is surrounded by two O atoms and two N atoms in the equatorial plane and two O atoms in axial positions, resulting in a distorted octa-hedral coordination geometry. There is an extensive three-dimensional network of O-H⋯O and N-H⋯O hydrogen bonds, which link the components.

(R)-2'-Benz-yloxy-5,5',6,6',7,7',8,8'-octa-hydro-1,1'-binaphthyl-2-ol.

The mol-ecules of the title compound, C(27)H(28)O(2), exhibit axial chirality. The planes of the aromatic rings of the tetra-lin ring systems make an angle of 85.72 (11)°. The non-aromatic rings adopt distorted half-chair conformations. In one of them, two C atoms of the four-atom aliphatic chain are disordered over two sites in a 0.75 (2):0.25 (2) ratio. The substituent phenyl ring is also disordered over two positions in a 0.59 (3):0.41 (3) ratio. There are no conventional hydrogen bonds joining the mol-ecules.

3-Oxoandrosta-4,6-dien-17beta-yl 2-methyl-1H-imidazole-1-carboxylate and 3-oxo-5alpha-androst-17beta-yl 2-methyl-1H-imidazole-1-carboxylate: C-H...pi and pi-pi intermolecular interactions.

The title compounds, C(24)H(30)N(2)O(3), (I), and C(24)H(34)N(2)O(3), (II), both contain an androstane backbone and a 2-methylimidazole-1-carboxylate moiety at the 17-position. Compound (I) contains two symmetry-independent molecules (denoted 1 and 2), while compound (II) contains just one molecule in the asymmetric unit. The C-C-O-C torsion angle that reflects the twisting of the 2-methylimidazole-1-carboxylate moiety from the mean steroid plane is 143.1 (2) degrees for molecule 1 of (I), 73.1 (3) degrees for molecule 2 of (I) and 86.63 (17) degrees for (II). The significance of this study lies in its observation of significant differences in both molecular conformation and supramolecular aggregation between the molecules of the title compounds. The solid-state conformations compared with those obtained theoretically from ab initio methods for the isolated molecules show large differences, especially in the orientation of the methylimidazole substituent.

N,N'-Bis-[(E)-(6-methyl-2-pyridyl)-methyl-ene]hexane-1,6-diamine.

The title compound, C(20)H(26)N(4), is composed of two (6-methyl-2-pyridyl)methyl-ene units linked by a 1,6-diamine hexane chain. The mol-ecule has C(i) symmetry with the inversion center situated at the mid-point of the central C-C bond. The alkyl chain has an all-trans conformation, with all the non-H atoms sharing the same plane [maximum deviation 0.004 (3) Å]. The pyridylmethyl-ene groups are also planar [maximum deviation 0.009 (3) Å], making an angle of 53.78 (19)° with the hexane chain plane. In the crystal, the mol-ecules assemble in layers, stacking along the a axis. The stacks are hold together by attractive interactions between π electron systems.

2,2',5,5'-Tetra-methyl-1,1'-(hexane-1,6-di-yl)di-1H-pyrrole.

The mol-ecule of the title compound, C(18)H(28)N(2), composed of two 2,5-dimethyl-pyrrole groups linked by a hexane chain, lies across a crystallographic inversion centre. The mean plane of the pyrrole ring is almost perpendicular to the mean plane of the central chain, making a dihedral angle of 89.09 (8)°. The crystal structure is stabilized by inter-molecular C-H⋯π inter-actions.

Conformation of 17-chloro-16-formylandrosta-5,16-dien-3beta-yl acetate and 17-chloroandrosta-5,16-dien-3beta-yl acetate.

In the title compounds, C(22)H(29)ClO(3), (I), and C(21)H(29)ClO(2), (II), respectively, the B rings adopt a half-chair conformation and the D rings adopt an envelope conformation. A twist of the steroid skeleton of both compounds is observed. There is a positional disorder of the acetoxy group of (II), with the terminal atoms disordered over two positions with near equal occupancy. Quantum-mechanical ab initio calculations using a molecular orbital Hartree-Fock method were performed for the isolated molecules, thus allowing the distinction within the structural features of these two androstane derivatives of which characteristics are intrinsic to the molecules and which are due to packing effects. The skeletal twisting was found to be innate to the molecules, while the acetoxy disorder is due to packing effects.

Bis(2,4,6-triamino-1,3,5-triazin-1-ium) bis-(4-hydroxy-pyridine-2,6-carboxyl-ato)-cuprate(II) hexa-hydrate.

In the title compound, (C(3)H(7)N(6))(2)[Cu(C(7)H(3)NO(5))(2)]·6H(2)O, the coordination geometry of the Cu(II) atom can be described as distorted octa-hedral. The equatorial plane is defined by four O atoms from two 4-hydroxy-pyridine-2,6-dicarboxyl-ate ligands. The axial positions are occupied by the N atoms of the same ligands. There is an extensive three-dimensional hydrogen-bond network reinforcing crystal cohesion.

Ethyl 3,5-dimethyl-1H-pyrrole-2-carboxyl-ate.

In the title compound, C(9)H(13)NO(2), there are two independent mol-ecules per asymmetric unit. The mol-ecules are very similar and almost planar, with the ethoxy-carbonyl group anti to the pyrrole N atom. The two independent mol-ecules are joined into dimeric units by strong hydrogen bonds between NH groups and carbonyl O atoms.

Bis[(2-quinol-yl)methane-diol-κN,O](sulfato-κO)copper(II) dihydrate.

In the title compound, [Cu(SO(4))(C(10)H(9)NO(2))(2)]·2H(2)O, the Cu(II) ion is chelated by two (2-quinol-yl)methane-diol ligands and coordinated by a monodentate sulfate ligand in a distorted trigonal-bipyramidal environment, with O atoms occupying the equatorial sites and N atoms in the axial sites. The dihedral angle between the two essentially planar quinoline ring systems is 45.02 (9)°. In the crystal structure, an extensive O-H⋯O hydrogen-bonding network forms layers parallel to the ab plane.

4-Amino-3,5-di-2-pyridyl-4H-1,2,4-triazole.

In the crystal structure of the title compound, C(12)H(10)N(6), the mol-ecules deviate slightly from planarity. The plane of the central triazole ring makes angles of 6.13 (9) and 3.28 (10)° with the pyridyl ring planes. Intra-molecular N-H⋯N inter-actions form six-membered closed rings. The crystal packing also shows weak C-H⋯π and C-H⋯N inter-actions.