Lamotrigine: Design and synthesis of new multicomponent solid forms.

In this work, a crystal engineering and thermodynamic based approach has been used aiming at contributing to a deeper knowledge of lamotrigine multicomponent solid forms. Two types of co-molecules have been chosen that can give rise to co-crystals with lamotrigine through different supramolecular heterosynthons: the xanthines, theophylline and caffeine, and the three isomeric pyridinecarboxamides. Association with diflunisal, which may result in a salt, was also investigated. Mechanochemistry, differential scanning calorimetry, thermogravimetry, X-ray powder and single crystal diffraction, infrared spectroscopy were the methods used. For all the systems, exploratory neat mechanochemistry experiments, carried out on lamotrigine + co-molecule binary mixtures of different compositions, were not successful in promoting association. From differential scanning calorimetry data and the binary solid-liquid phase diagrams, co-crystals/salts were identified as well as their respective stoichiometry, and a methodology of synthesis was established. For pyridinecarboxamides, molecular recognition is dependent on the position of the amide group in the pyridine ring: co-crystallization did not occur with picolinamide co-former. Both xanthines form co-crystals with lamotrigine, (1:1) with theophylline and (2:1) lamotrigine:caffeine. Additionally, the crystalline structure of a lamotrigine:theophylline 1:1 monohydrate was solved. The (1:1) lamotrigine:theophylline co-crystal converts to this monohydrate in accelerated stability tests. A (1:1) lamotrigine:diflunisal salt was identified, which proved to be stable in accelerated stability assays.

Effect of the capping ligand on luminescent erbium(III) ß-diketonate single-ion magnets.

Erbium complexes featuring ß-diketonate ligand 2,4-hexanedione (Hh) and N,N-donor-ligands 2,2'-bipyridine (bipy), 5-nitro-1,10-phenanthroline (5NO2phen) and bathophenanthroline (bath) have been synthesized. The structures of the ternary complexes [Er(h)3(bipy)], [Er(h)3(5NO2phen)] and [Er(h)3(bath)] have been determined by single crystal X-ray diffraction. Excitation of the complexes in the ultraviolet region (337 nm) led to near infrared (NIR) luminescence at 1532 nm characteristic of the trivalent erbium ion in the three compounds, with an improved antenna effect in the 5-nitro-1,10-phenanthroline complex. The AC susceptibility studies conducted at frequencies ranging from 33 to 9995 Hz and at temperatures in the 1.7 to 10 K range revealed that the application of a static magnetic field induces a slow magnetic relaxation in all three compounds. The complex with the bulkier capping ligand (bathophenanthroline) exhibits the highest energy barrier U/k(B) = 23 K.

8-Iodo-5,7-dimeth-oxy-4-methyl-2H-chromen-2-one.

In the title compound, C(12)H(11)IO(4), the C and O atoms of both meth-oxy groups lie very close to the mean plane of the six C atoms of the benzene ring. The O and C atoms of the group lying closest to the I atom are 0.012 (3) and 0.022 (4) Å, respectively, out of the mean plane. For the other meth-oxy group, the corresponding distances are 0.020 (3) and 0.078 (4) Å. In the crystal, there are only very weak inter-molecular C-H⋯O hydrogen bonds and O⋯I contacts [3.080 (2) Å]. The mol-ecules are approximately parallel to (100), forming a layered structure.

Erythritol: crystal growth from the melt.

The structural changes occurring on erythritol as it is cooled from the melt to low temperature, and then heated up to the melting point have been investigated by differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM), X-ray powder diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR). By DSC, it was possible to set up the conditions to obtain an amorphous solid, a crystalline solid, or a mixture of both materials in different proportions. Two crystalline forms have been identified: a stable and a metastable one with melting points of 117 and 104 degrees C, respectively. The fusion curve decomposition of the stable form revealed the existence of three conformational structures. The main paths of the crystallization from the melt were followed by PLTM. The texture and colour changes allowed the characterization of the different phases and transitions in which they are involved on cooling as well as on heating processes. The type of crystallization front and its velocity were also followed by microscopic observation. These observations, together with the data provided by PXRD, allowed elucidating the transition of the metastable form into the stable one. The structural changes occurring upon the cooling and subsequent heating processes, namely those arising from intermolecular hydrogen bonds, were also accompanied by infrared spectroscopy. Particular attention was given to the spectral changes occurring in the OH stretching region.

Bis(2-amino-6-methyl-pyrimidin-1-ium-4-olate-κN,O)bis-(nitrato-κO,O')cadmium(II).

In the title compound, [Cd(NO(3))(2)(C(5)H(7)N(3)O)(2)], the Cd(II) atom is eight-coordinated by two amine N atoms and two O atoms from two zwitterionic, biodentate 2-amino-6-methyl-pyrimidin-1-ium-4-olate ligands and by four O atoms from two nitrate groups. Intra-molecular N-H⋯O hydrogen bonds occur. The crystal packing is stabilized by inter-molecular N-H⋯O and C-H⋯O hydrogen bonds, two of which are bifurcated, between the nitrate anions and the organic groups.

Guanidinium 4-amino-benzoate.

In the title compound, CH(6)N(3) (+)·C(7)H(6)NO(2) (-), the cation and anion lie on crystallographic mirror planes. The 4-amino-benzoate anion is almost in a planar conformation with a maximum deviation of 0.024 (2) Šfor the N atom. The bond length in the deprotonated carboxyl group is inter-mediate between those of normal single and double Csp(2)=O bonds, indicating delocalization of the charge over both O atoms of the COO(-) group. In the crystal, N-H⋯O hydrogen bonds assemble the ions in layers propagating in the bc plane. This structure is very similar to that of guanidinium benzoate.

6,8-Diiodo-5,7-dimeth-oxy-4-methyl-coumarin.

In the title compound, C(12)H(10)I(2)O(4), the meth-oxy groups are twisted considerably with respect to the plane of the aromatic ring [CH(3)-O-C-C torsion angles = -85.9 (3) and -92.8 (3)°]. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds and O⋯I contacts [3.194 (2) Å].

Bis[2-amino-6-methyl-pyrimidin-4(1H)-one-κN,O]dichloridocadmium(II).

In the title compound, [CdCl(2)(C(5)H(7)N(3)O)(2)], the Cd(II) atom is six-coordinated by two heterocyclic N atoms [Cd-N = 2.261 (2) and 2.286 (2) Å] and two O atoms [Cd-O = 2.624 (2) and 2.692 (2) Å] from two bidentate chelate 2-amino-6-methyl-pyrimidin-4(1H)-one ligands and two chloride ions [Cd-Cl = 2.4674 (6) and 2.4893 (7) Å]. The crystal packing is characterized by an open-framework architecture with the crystal packing stabilized by inter-molecular N-H⋯Cl and N-H⋯O hydrogen bonds.

7,7'-Dihy-droxy-4,4'-dimethyl-3,4-dihydro-2H,2'H-4,6'-bichromene-2,2'-dione.

The title compound, C(20)H(16)O(6), which contains one chiral centre, crystallizes as a racemate. The mean planes of the two coumarin units make a dihedral angle of 88.07 (2)°. The pyrone ring containing the chiral centre adopts a sofa conformation. In the crystal, four mol-ecules are linked by O-H⋯O hydrogen bonds, forming a tetrameric ring with graph-set motif R(4) (4)(32). These tetramers are further linked by O-H⋯O hydrogen bonds into a three-dimensional network.

6beta-Hydroxy-5beta-methyl-20-oxo-19-norpregn-9(10)-en-3beta-yl acetate.

In the title compound, C(23)H(34)O(4), which is an intermediate in the synthesis of pregnane derivatives with a modified skeleton that show potent abortion-inducing activity, the conformation of ring B is close to half-chair due to the presence of both the C=C double bond and the axial 5beta-methyl group. Rings A and C have conformations close to chair, while ring D has a twisted conformation around the bridgehead C-C bond. Molecules are hydrogen bonded via the hydroxyl and acetoxy groups into infinite chains. Quantum-mechanical ab initio Roothan Hartree-Fock calculations show that crystal packing might be responsible for the low values of the angles between rings A and B, and between ring A and rings C and D, as well as for a different steric position of the methyl ketone side chain compared to the geometry of the free molecule.

1,5-Bis(2,5-dimethyl-1H-pyrrol-1-yl)naphthalene.

In the title compound, C(22)H(22)N(2), the asymmetric unit contains one half-mol-ecule. A crystallographic inversion centre is located at the mid-point of the bond common to both rings, in the central naphthalene unit. Quantum-mechanical ab initio calculations on the isolated mol-ecule showed that the minimum energy configuration occurs when the naphthalene ring system and the pyrrolyl groups deviate only slightly from perpendicularity. In the crystal, due to the effects of crystal packing, the mol-ecule deviates by approximately 4° from the a priori expected ideal value of 90° [C-C-N-C torsion angle = 86.11 (15)°].

N,N',N''-Triphenyl-guanidinium 5-nitro-2,4-dioxo-1,2,3,4-tetra-hydro-pyrimidin-1-ide.

In the title compound, C(19)H(18)N(3) (+.)C(4)H(2)N(3)O(4) (-), the dihedral angles between the phenyl rings and the plane defined by the central guanidinium fragment are in the range 41.3 (1)-66.6 (1)°. The pyrimidine ring of the anion is distorted towards a boat conformation and the nitro group is rotated 11.4 (2)° out of the uracil plane. Hydrogen bonds assemble the ions in infinite helical chains along the b axis.

A new polymorph of 5-nitro-uracil monohydrate.

In the title compound, C(4)H(3)N(3)O(4)·H(2)O, mol-ecules of 5-nitro--uracil are hydrogen bonded in pairs across crystallographic centers of symmetry. The resulting dimers are also hydrogen bonded to the water mol-ecules, forming a three-dimensional network. The pyrimidine ring is almost planar (with a maximum deviation of 0.0156 (9) Šfor the one of the N atoms) and the nitro group is rotated by 12.4 (1)° out of the uracil plane, while in the other polymorph the value for the same angle is 5°.

Bis(triphenyl-guanidinium) tetra-chlorido-cuprate(II).

The structure of the title compound, (C(19)H(18)N(3))(2)[CuCl(4)], consists of square-planar [CuCl(4)](2-) anions and triphenyl-guanidinium cations. The Cu(II) ion occupies a crystallographic inversion centre. In the cation, the dihedral angles between the phenyl rings and the plane defined by the central guanidinium fragment are in the range 51.9 (4)-64.4 (3)°. N-H⋯Cl hydrogen bonds assemble the ions into infinite chains running along the b axis.

6ß-Acetamido-5α-hydroxy-cholestan-3ß-yl acetate.

The title steroid, C(31)H(53)NO(4), was prepared from the corresponding 5α,6α-epoxy-cholestane. The conformation of the six-membered rings is close to a chair form, while the five-membered ring adopts a twist conformation. The hydroxyl and acetamide groups are in axial positions. The nucleophilic species bound to the steroid nucleus at position 6 by the ß-face, whereas the hydroxyl group at position 5 has α-orientation. All rings are trans-fused. The crystal packing shows that the mol-ecules related by twofold symmetry exist as O-H⋯O hydrogen-bonded dimers.

Weak antiferromagnetic interactions in hydronium diaqua-1kappaO,2kappaO-trichloro-1kappaCl,2kappa2Cl-mu-dimethylglycinato-1kappaO:2kappa2O',N-dimethylglycinato-1kappa2N,O-dicuprate(II).

The crystal structure of the title compound, (H3O)[Cu2(C4H8NO2)2Cl3(H2O)2], contains two Cu(II) ions bridged by the carboxylate group of a dimethylglycinate ion in an anti-anti configuration. The Cu(II) atoms both have an approximately square-pyramidal conformation geometry and are 5.977 (2) angstroms apart. The two dimethylglycinate ligands have similar conformations, although they play different roles in the structure. A weak antiferromagnetic interaction between the two copper ions could be inferred from the magnetic susceptibility measurements.

Di-mu-chloro-1:2kappa2Cl;3:4kappa2Cl-hexachloro-1kappa3Cl,4kappa3Cl-tetra-mu-dimethylglycine-2:3kappa8O:O'-tetracopper(II).

The title compound, [Cu(NO3)2(C6H10N4)2], crystallizes in the centrosymmetric space group P21/c with a unit cell containing two tetranuclear copper(II) complexes sited on crystallographic inversion centres. The coordination geometry around the central Cu atoms is square pyramidal, with four O atoms in the basal plane and a Cl atom in the apical position. The lateral CuCl4 groups are flattened tetrahedral. The bridging dimethylglycine molecules are present in the dipolar zwitterionic form. The tetranuclear copper complexes exist as isolated entities since only intramolecular hydrogen bonds are found.

Synthesis, structure, thermal and non-linear optical properties of L-argininium hydrogen selenite.

L-Argininium hydrogen selenite (C(6)H(15)N(4)O(2)HSeO(3)) is a new semiorganic compound of the hydrogen selenite family with non-linear optical properties. The crystal lattice is monoclinic with unit-cell parameters a = 22.493 (5), b = 5.1624 (13), c = 9.730 (4) A, beta = 95.68 (3) degrees, V = 1124.3 (6) A(3), Z = 4, space group C2. Second-harmonic generation measurements performed on powder samples, using a Q-switched Nd:Yag laser (lambda = 1064 nm), showed the second-harmonic power to be about twice that of urea. Differential scanning calorimetry measurements revealed the existence of a phase transition with onset at 289 K.

Strong hydrogen-bonded amino acid dimers in L-alanine alaninium nitrate.

The title compound, C3H7NO2*C3H8NO2+*NO3-, contains L-alanine-alaninium dimers bonded via the carboxyl groups by a strong asymmetric hydrogen bond with an O...O distance of 2.4547 (19) A. The neutral alanine molecule exists as a zwitterion, where the carboxyl group is dissociated and the amino group is protonated. The alaninium cation has both groups in their acidic form. The alanine molecule and the alaninium cation differ only slightly in their conformation, having an N-C(alpha)-C=O torsion angle close to -25 degrees. The dimers and the nitrate anion are joined through a three-dimensional hydrogen-bond network, in which the full hydrogen-bonding capabilities of the amino groups of the two alanine moieties are realised.