Characterization of a new solvate of risedronate

Three new forms of the osteoporosis drug sodium risedronate, sodium [1-hydroxy-2-(3-pyridinyl)ethylidene]bisphosphonate, were identified and designated as the J, K, and M phases. Form J is an acetic acid disolvate with the chemical composition Na(+) [C(7) H(10) NO(7) P(2)](-) · 2CH(3) COOH, as determined by single-crystal structure analysis. This novel solvate is easily formed by the recrystallization of sodium risedronate from acetic acid. Dissolution of the new disolvate was characterized in distilled water, a compendial buffer, simulated gastric fluid sine pepsin (pH 1.2), and a biorelevant buffer system FaSSIF-V2 (pH 6.8). It was demonstrated that solubility of the disolvate in physiological buffers differed significantly from that of the original molecule, with delayed dissolution under simulated esophageal and gastric conditions, but rapid and complete dissolution under simulated intestinal conditions. These studies suggest that through the generation of novel solvates, the biopharmaceutical properties of poorly soluble drug candidates can be improved.

2-Amino-1-methyl-1H-imidazol-4(5H)-one dimethyl sulfoxide monosolvate

In the title compound, C(4)H(7)N(3)O·C(2)H(6)OS, creatinine [2-amino-1-methyl-1H-imidazol-4(5H)one] exists in the amine form. The ring is planar (r.m.s. deviation for all non-H atoms = 0.017 Å). In the crystal, two creatinine mol-ecules form centrosymmetric hydrogen-bonded dimers linked by pairs of N-H⋯N hydrogen bonds. In addition, creatinine is linked to a dimethyl sulfoxide mol-ecule by an N-H⋯O inter-action. The packing shows layers parallel to (120).

1-(4-Fluoro-phen-yl)biguanid-1-ium chloride

The title compound, C₈H₁₁FN₅⁺·Cl⁻, crystallized with a monoprotonated 1-(4-fluoro­phen­yl)biguanidinium cation and a chloride anion in the asymmetric unit. The biguanidium group is not planar [dihedral angle between the two CN₃ groups = 52.0 (1)°] and is rotated with respect to the phenyl group [τ = 54.3 (3)°]. In the crystal, N—H⋯N hydrogen-bonded centrosymmetric dimers are connected into ribbons, which are further stabilized by N—H⋯Cl interactions, forming a three-dimensional hydrogen-bonded network.

17-Acetoxymulinic acid

The title compound, [systematic name: 5a-acet­oxy­methyl-3-isopropyl-8-methyl-1,2,3,3a,4,5,5a,6,7,10,10a,10b-dodeca­hydro-7,10-endo-epidi­oxy­cyclo­hepta­[e]indene-3a-carb­oxy­lic acid], C₂₂H₃₂O₆ (I), is closely related to methyl 5a-acet­oxy­methyl-3-isopropyl-8-methyl-1,2,3,3a,4,5,5a,6,7,10,10a,10b-dodeca­hydro-7,10-endo-epidi­oxy­cyclo­hepta­[e]indene-3a-carboxyl­ate, (II) [Brito et al., (2008 ▶). Acta Cryst. E64, o1209]. There are two mol­ecules in the asymmetric unit, which are linked by two strong intra­molecular O—H⋯O hydrogen bonds with graph-set motif R₂²(8). In both (I) and (II), the conformation of the three fused rings are almost identical. The five-membered ring has an envelope conformation, the six-membered ring has a chair conformation and the seven-membered ring has a boat conformation. The most obvious differences between the two compounds is the observed disorder of the acet­oxy­methyl fragments in both mol­ecules of the asymmetric unit of (I). This disorder is not observed in (II). The crystal structure and the molecular conformation is stabilized by intermolecular C—H⋯O hydrogen bonds. The ability to form hydrogen bonds is different in the two compounds. The crystal studied was a non-merohedral twin, the ratio of the twin components being 0.28 (1):0.72 (1)

Monothioindigo, determined by microcrystal structure analysis

Indigo and thioindigo pigments are used for a wide range of applications. The crystal structure of the mixed compound monothioindigo [systematic name: (E)-2-(3-oxo-2,3-dihydro-1-benzothiophen-2-ylidene)-2,3-dihydro-1H-indol-3-one], C(16)H(9)NO(2)S, has been determined by microcrystal structure analysis from a crystal with a size of just 1 x 2 x 10 microm. The crystal structure of monothioindigo resembles those of indigo and thioindigo. The molecules show orientational disorder, with site-occupation factors of 0.962 (2) and 0.038 (2) for the major and minor disorder components, respectively. The indigo fragment donates an intermolecular hydrogen bond, leading to a criss-cross arrangement of molecules similar to that in indigo, whereas the thioindigo fragment exhibits only van der Waals interactions and molecular stacking, similar to that in thioindigo.

Trithia-cyanuric acid: a second triclinic polymorph

The title compound, C(3)H(3)N(3)S(3), is a triclinic modification. The other reported modification crystallizes with just one mol-ecule in the asymmetric unit, [Guo et al. (2006 ▶). Cryst. Growth Des.6, 846-848] and was solved by power X-ray diffraction data. The present modification has Z' = 2. In the crystal, mol-ecules are linked by strong intra-molecular N-H⋯S hydrogen bonds with set graph-motif R(2) (2)(8). In both mol-ecules, all of the N atoms and two of the S atoms are involved in hydrogen bonding, with an average H⋯S distance of 2.58 Å and N-H⋯S angles in the range 163-167°. π-π stacking inter-actions are not observed. In the solid state, the mol-ecules exist in the thione form. The mol-ecular and supra-molecular properties are similar in both polymorphs.

Poly[diaqua[3,5-bis(trifluoromethyl)pyrazolido]potassium]

The asymmetric unit of the title compound, [K(C₅HF₆N₂)(H₂O)₂]_n, is composed of two 3,5-bis­(trifluoro­meth­yl)pyrazol­ide anions, two potassium cations and four water mol­ecules. The water mol­ecules and 3,5-bis­(trifluoro­meth­yl)pyrazolide anions act as bridges between the potassium cations. Each potassium cation is surrounded by four O atoms [K—O = 2.705 (3)–2.767 (3) Å] and four F atoms [K—F = 2.870 (7)–3.215 (13) Å]. The water mol­ecules and the 3,5-bis­(trifluoro­meth­yl)pyrazolide anions are connected by O—H⋯N hydrogen bonds, forming layers in the ab plane. All –CF₃ groups show rotational disorder between two orientations each.

1-(4-Methoxyphenyl)-2-(1H-1,2,4-triazol-1-yl)ethanone

In the title compound, C₁₁H₁₁N₃O₂, the dihedral angle between the central ethanone fragment and the 4-meth­oxy­phenyl group is 2.9 (2)°, while that between the ethanone fragment and the triazole ring is 83.4 (2)°. The dihedral angle between the planes of the triazole and benzene rings is 81.7 (1)°. The 4-meth­oxy­phenyl group is cis with respect to the ethanone fragment O atom across the exocyclic C—C bond. In the crystal, mol­ecules are linked by C—H⋯N inter­actions into C(9) chains along [001].

1,1'-(9-Octyl-9H-carbazole-3,6-di-yl)diethanone

The central structural element of the title compound, C₂₄H₂₉NO₂, is a carbazole unit substituted with two acetyl residues and an octyl chain. The acetyl residues are nearly coplanar [dihedral angles = 5.37 (14) and 1.0 (3)°] with the carbazole unit which is essentially planar (r.m.s. deviation for all non-H atoms = 0.025 Å). The octyl chain adopts an all-trans conformation. The crystal packing is stabilized by C—H⋯O hydrogen bonds.

Fourth generation scorpionates: coordination behavior of a new class of conformationally flexible mixed-donor (pyrazol-1-yl)borates

The coordination behavior, the conformational flexibility, and the stability of the novel (pyrazol-1-yl)borate ligands [Ph(pz)B(mu-N(Me))(mu-pz)B(pz)Ph](-) ([L(1)](-)), [Ph(pz)B(mu-O)(mu-pz)B(pz)Ph](-) ([L(2)](-)), and [Ph(pz)B(mu-O)(mu-OB(Ph)O)B(pz)Ph](2-) ([L(3)](2-)) have been experimentally assessed by investigating the following compounds: [Li(thf)L(1)], [Li(thf)L(2)], [Mg(Cl)(thf)(x)L(1)], [Mg(Cl)(thf)(2)L(2)], [Mn(CO)(3)L(2)], K(thf)[Mn(CO)(3)L(3)], [CoCl(2)(HL(1))], [L(1)Co(mu-Cl)(2)CoL(1)], [Zn(Br)L(1)], [Cu(Cl)L(1)], [Cu(Cl)L(2)]. The L(1)-complexes were prepared from a mixture of HL(1) and the appropriate metal salt by addition of a base. HCl elimination from [CoCl(2)(HL(1))], which gives [L(1)Co(mu-Cl)(2)CoL(1)], does not necessarily require the assistance of a base, but happens spontaneously when a solution of the complex is stored at room temperature for several days. K(thf)[Mn(CO)(3)L(3)] was obtained via in situ hydrolysis of HL(1)/[Mn(CO)(5)Br] in the presence of K(2)CO(3). In some other cases, formation of the coordination compounds proceeded with decomposition of a part of the ligand molecules and yielded pyrazole (e.g., [Zn(Cl)(Hpz)L(2)]) or pyrazolide (e.g., [L(2)Co(mu-Cl)(mu-pz)CoL(2)]) complexes. As evidenced by the crystal structure analyses of [Zn(Br)L(1)]/[Mg(Cl)(thf)(2)L(2)]/[Mn(CO)(3)L(2)] on the one hand and [L(1)Mg(mu-Cl)(2)Mg(thf)L(1)]/[Cu(Cl)L(1)]/[Cu(Cl)L(2)](2) on the other, [L(1)](-) and [L(2)](-) are able to adopt both a facial and a meridional conformation. Moreover, while many of the established design principles of scorpionate chemistry are still valid for [L(1)](-), [L(2)](-), and [L(3)](2-), the bonding situation of the central donor moiety (N(Me) in [L(1)](-); O in [L(2)](-), [L(3)](2-)) is distinctly different from the way the pyrazolyl rings are attached to the molecule, so that donor scrambling is not an issue in these [N,N,N] and [N,O,N] mixed-donor ligands.

Solvent-free mesityllithium: solid-state structure and its reactivity towards white phosphorus

The donor-free mesityllithium was prepared from the reaction of MesBr with n-BuLi in diethyl ether at -78 degrees C. The solid-state structure of unsupported mesityllithium consists of C(2)Li(2)-rings composed of two LiMes units, which interact with adjacent dimers [LiMes](2), forming a polymeric infinite chain along the crystallographic c-axis (monoclinic space group, P2(1)/n). The structure of donor-free mesityllithium reveals short contacts between the C atoms of the mesityl rings and the lithium atoms of neighbouring [LiMes](2) units. The structure determination of LiMes was performed by X-ray powder diffraction. In addition we have investigated the reaction of LiMes with Me(3)SnCl and P(4) for our understanding of the reactivity of donor-free mesityllithium. The heterogeneous reaction of donor-free mesityllithium with Me(3)SnCl produces conveniently the stannylated mesitylene Me(3)SnMes (triclinic, space group P1). White phosphorus reacts with three equivalents of unsupported mesityllithium in benzene to give Li(3)P(4)Mes(3). In this context it should be noted that a tetraphosphide with an identical LiP-core as in Li(3)P(4)Mes(3) had been formed in the 1:3 reaction of P(4) with the silanide Li[SitBu(3)]. The tetraphosphide Li(3)P(4)Mes(3) was analyzed using X-ray crystallography (monoclinic, space group C2/c).

Structural comparison of three N-(4-halogenophenyl)-N'-[1-(2-pyridyl)ethylidene]hydrazine hydrochlorides

2-{1-[(4-Chloroanilino)methylidene]ethyl}pyridinium chloride methanol solvate, C(13)H(13)ClN(3)(+) x Cl(-) x CH(3)OH, (I), crystallizes as discrete cations and anions, with one molecule of methanol as solvent in the asymmetric unit. The N-C-C-N torsion angle in the cation indicates a cis conformation. The cations are located parallel to the (\overline{2}02) plane and are connected through hydrogen bonds by a methanol solvent molecule and a chloride anion, forming zigzag chains in the direction of the b axis. The crystal structure of 2-{1-[(4-fluoroanilino)methylidene]ethyl}pyridinium chloride, C(13)H(13)FN(3)(+) x Cl(-), (II), contains just one anion and one cation in the asymmetric unit but no solvent. In contrast with (I), the N-C-C-N torsion angle in the cation corresponds with a trans conformation. The cations are located parallel to the (100) plane and are connected by hydrogen bonds to the chloride anions, forming zigzag chains in the direction of the b axis. In addition, the crystal packing is stabilized by weak pi-pi interactions between the pyridinium and benzene rings. The crystal of (II) is a nonmerohedral monoclinic twin which emulates an orthorhombic diffraction pattern. Twinning occurs via a twofold rotation about the c axis and the fractional contribution of the minor twin component refined to 0.324 (3). 2-{1-[(4-Fluoroanilino)methylidene]ethyl}pyridinium chloride methanol disolvate, C(13)H(13)FN(3)(+) x Cl(-) x 2 CH(3)OH, (III), is a pseudopolymorph of (II). It crystallizes with two anions, two cations and four molecules of methanol in the asymmetric unit. Two symmetry-equivalent cations are connected by hydrogen bonds to a chloride anion and a methanol solvent molecule, forming a centrosymmetric dimer. A further methanol molecule is hydrogen bonded to each chloride anion. These aggregates are connected by C-H...O contacts to form infinite chains. It is remarkable that the geometric structures of two compounds having two different formula units in their asymmetric units are essentially the same.

(18-Crown-6)(trifluoro-methane-sulfonato)-sodium

The title compound, [Na(CF(3)O(3)S)(C(12)H(24)O(6))], features a sodium cation that is coordinated by eight O atoms in an irregular hexa-gonal bipyramidal environment. The equatorial positions are occupied by the six O atoms of an 18-crown-6 ether ring. In the axial positions, there is one O atom of a trifluoro-methane-sulfonate anion and an ether O atom of a symmetry-equivalent crown ether ring. In this way, centrosymmetric dimers are formed.