RESUMEN

Three novel coordination compounds based on α,α-disubstituted analogues of zoledronic acid with a cyclopropane (cpp) or cyclobutane (cbt) ring on the Cα carbon, isomorphous [Co(H2cppZol)(H2O)]·H2O (1a), [Ni(H2cppZol)(H2O)]·H2O (1b) and [Co(H2cbtZol)(H2O)]·H2O (2a), were synthesized under hydrothermal conditions at low pH. Single-crystal X-ray diffraction analysis revealed that all the compounds had a 1D double zig-zag chain architecture with an 8 + 8 ring motif formed by alternately arranged symmetrical (-O-P-O-)2 bridges linking equivalent octahedral metal centres. Both the ligand coordination mode and chain architecture displayed by 1a, 1b and 2a are unique among 1D [M(H2L)(H2O) x ]·yH2O coordination polymers based on nitrogen-containing bisphosphonates reported so far. All the compounds exhibit similar decomposition pathways upon heating with thermal stabilities decreasing in the order 1b > 1a > 2a. The IR spectra revealed that lattice water release above 227, 178 and 97 °C, respectively, does not change the chain architecture leaving them intact up to ca. 320, 280 and 240 °C. Magnetic behaviour investigations indicated that 1a, 2a and 1b exhibit weak alternating antiferromagnetic-ferromagnetic exchange interactions propagated between the magnetic centres through double (-O-P-O-)2 bridges. The boundary between antiferro- and ferromagnetic couplings for the Co-O⋯O-Co angle in 1a and 2a was estimated to be ca. 80°. This value is also applicable for recently reported [M3(HL)2(H2O)6]·6H2O (M = Co, Ni) complexes based on α,α-disubstituted analogues of zoledronic acid and can be used to the explain magnetic behaviour of 1b.

RESUMEN

Two novel α,α-disubstituted derivatives of zoledronic acid, namely 1-hydroxy-2-(1H-imidazol-1-yl)-2-methylpropylidene-1,1-diphosphonic acid (H4L1) and 1-hydroxy-2-[1-(1H-imidazol-1-yl)cyclopropyl]ethylidene-1,1-diphosphonic acid (H4L2) were synthesized and structurally characterized by single-crystal X-ray diffraction. The reaction of cobalt acetate with H4L1 and H4L2 carried out under hydrothermal conditions afforded two isomorphous Co3(HL1)2(H2O)6·6H2O (1a) and Co3(HL2)2(H2O)6·6H2O (2a) complexes. Both compounds are characterized by means of X-ray crystallography, IR and NIR-Vis-UV spectroscopic methods. Furthermore, their magnetic properties and thermal stabilities are reported. The crystals of 1a and 2a feature infinite 1D polymeric chains built from alternately arranged dinuclear [Co2(HL1/HL2)(H2O)2]2 units and {Co1O6} octahedra running along the [1[combining macron]10] crystallographic direction. In both compounds, crystallographically distinct Co1 and Co2 atoms are six-coordinated. As is reflected in T values (T - index of tetragonality), the coordination environment of Co1 generates a slightly elongated octahedron (T = 0.94), whereas a slightly compressed octahedron (T = 1.06 for 1a and 1.05 for 2a) is formed around Co2. An assumption that the d-d type absorption is mainly attributed to the inversion related Co2 centers, whose population is two times higher than that of Co1, afforded a good correlation between calculated transition energies and experimental NIR-Vis-UV spectra. The magnetic susceptibility measurements analyzed in terms of a spin-3/2 Heisenberg trimer chain revealed that Co1Co2 interactions within the trimer are antiferromagnetic whereas Co2Co2 intertrimer interactions are ferromagnetic.

RESUMEN

In the title mol-ecular salt, C12H24N(+)·NO3 (-), the cyclohexyl rings adopt chair conformations with the exocyclic C-N bonds in equatorial orientations. In the crystal, a bifurcated N-H⋯(O,O) hydrogen bond links the cation to the anion; the ion pairs are linked via C-H⋯O hydrogen bonds, forming layers in the ac plane.

RESUMEN

The asymmetric unit of the title salt, C12H24N(+)·C2H2BrO2(-), contains a dicyclohexylammonium cation connected to a bromoacetate anion by means of an N-H...O hydrogen bond. In the crystal, the ion pairs assemble via N-H...O interactions, forming zigzag infinite chains parallel to the c axis with the (...H-N-H...O-C-O...)n motif that is considered to be a prerequisite for ensuring gelation properties of secondary ammonium monocarboxylate salts. The title salt was characterized by FT-IR, X-ray powder diffraction (XRPD), TG-DTA and (1)H NMR spectroscopy in solution. Gelation experiments revealed that dicyclohexylammonium bromoacetate forms molecular gels with dimethylformamide and dimethyl sulfoxide. Scanning electron microscopy (SEM) was used to reveal morphological features of dried gels.

RESUMEN

Genistein, a naturally occurring polyphenolic compound, was combined with isonicotinamide, a pharmaceutically acceptable coformer, to yield a 1:2 cocrystal [systematic name: 5,7-dihydroxy-3-(4-hydroxyphenyl)chromen-4-one-pyridine-4-carboxamide (1/2)], C15H10O5·2C6H6N2O. The molecules in the cocrystalline phase are present in their neutral forms, and assemble a molecular layer by means of hydrogen bonding.

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RESUMEN

Cocrystallization of baicalein with nicotinamide yields a 1:1 cocrystal [systematic name: pyridine-3-carboxamide-5,6,7-trihydroxy-2-phenyl-4H-chromen-4-one (1/1)], C(6)H(6)N(2)O·C(15)H(10)O(5). The asymmetric unit contains one baicalein and one nicotinamide molecule, both in neutral forms. Molecules in the cocrystal form column motifs stabilized by an array of intermolecular hydrogen bonds.

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RESUMEN

In the crystal structures of the conformational isomers hydrogen {phosphono[(pyridin-1-ium-3-yl)amino]methyl}phosphonate monohydrate (pro-E), C(6)H(10)N(2)O(6)P(2)·H(2)O, (Ia), and hydrogen {phosphono[(pyridin-1-ium-3-yl)amino]methyl}phosphonate (pro-Z), C(6)H(10)N(2)O(6)P(2), (Ib), the related hydrogen {[(2-chloropyridin-1-ium-3-yl)amino](phosphono)methyl}phosphonate (pro-E), C(6)H(9)ClN(2)O(6)P(2), (II), and the salt bis(6-chloropyridin-3-aminium) [hydrogen bis({[2-chloropyridin-1-ium-3-yl(0.5+)]amino}methylenediphosphonate)] (pro-Z), 2C(5)H(6)ClN(2)(+)·C(12)H(16)Cl(2)N(4)O(12)P(4)(2-), (III), chain-chain interactions involving phosphono (-PO(3)H(2)) and phosphonate (-PO(3)H(-)) groups are dominant in determining the crystal packing. The crystals of (Ia) and (III) comprise similar ribbons, which are held together by N-H···O interactions, by water- or cation-mediated contacts, and by π-π interactions between the aromatic rings of adjacent zwitterions in (Ia), and those of the cations and anions in (III). The crystals of (Ib) and (II) have a layered architecture: the former exhibits highly corrugated monolayers perpendicular to the [100] direction, while in the latter, flat bilayers parallel to the (001) plane are formed. In both (Ib) and (II), the interlayer contacts are realised through N-H···O hydrogen bonds and weak C-H···O interactions involving aromatic C atoms.

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RESUMEN

The solution properties of a series of (pyridin-2-yl)aminomethane-1,1-diphosphonic acids 1-4 as well as closely related compounds 5 and 6 with 1,3-thiazolyl or 1,3-benzothiazolyl side chains and their influence on the complexation of Zn(II), Mg(II) and Ca(II) were studied by means of the 31P and 1H NMR spectroscopy, pH-potentiometry and ESI-MS methods. The crystal structures of 5 and 6 were determined by X-ray analysis. All the studied compounds exist in solution as mixtures of the Z and E isomers with respect to the C2-Namino bond. Compounds 1 and 2 exhibit higher overall basicities compared to 3-6 and have exceptionally basic pyridyl nitrogen (pK2 = 7.88 and 8.18, respectively). Dynamic NMR studies revealed that the nature of the aromatic side chain as well as the specificity and topology of the ring substituent account for the rotational barrier for the Z/E interconversion, which decreases in the order of 1 approximately 2 > 3 approximately 4 >> 5 (6). This is particularly important for aggregational properties of 1-6 in solution and for the complex-formation equilibria. Overall, compounds 1-6 demonstrate a strong tendency for the formation of protonated multinuclear complexes. Their formation is unexpectedly slow on the NMR time scale compared to previously studied bisphosphonate complexes. The stepwise release of protons upon the rise of pH leads to mononuclear species. The Z ligand conformation is preferred in multinuclear complexes of Zn(II), Mg(II) and Ca(II) with 1 and 2 whereas in the case of 3-6 the complexation processes are affected by the intramolecular Z/E interconversion.

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RESUMEN

The crystal structures of two salts, products of the reactions between [(5-methyl-2-pyridyl)aminomethylene]bis(phosphonic acid) and 4-aminopyridine or ammonia, namely bis(4-aminopyridinium) hydrogen [(5-methyl-2-pyridinio)aminomethylene]diphosphonate 2.4-hydrate, 2C(5)H(7)N(2)(+).C(7)H(10)N(2)O(6)P(2)(2-).2.4H(2)O, (I), and triammonium hydrogen [(5-methyl-2-pyridyl)aminomethylene]diphosphonate monohydrate, 3NH(4)(+).C(7)H(9)N(2)O(6)P(2)(3-).H(2)O, (II), have been determined. In (I), the Z configuration of the ring N-C and amino N-H bonds of the bisphosphonate dianion with respect to the C(ring)-N(amino) bond is consistent with that of the parent zwitterion. Removing the H atom from the pyridyl N atom results in the opposite E configuration of the bisphosphonate trianion in (II). Compound (I) exhibits a three-dimensional hydrogen-bonded network, in which 4-aminopyridinium cations and water molecules are joined to ribbons composed of anionic dimers linked by O-H...O and N-H...O hydrogen bonds. The supramolecular motif resulting from a combination of these three interactions is a common phenomenon in crystals of all of the Z-isomeric zwitterions of 4- and 5-substituted (2-pyridylaminomethylene)bis(phosphonic acid)s studied to date. In (II), ammonium cations and water molecules are linked to chains of trianions, resulting in the formation of double layers.

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RESUMEN

The title compound, C6H9BrN2O6P2, a micromolar inhibitor of the farnesyl pyrophosphate synthase, is a Z-isomer zwitterion with one negative phosphonate group and a protonated pyridine N atom. Two types of ribbons, both parallel to the a axis, formed by several centrosymmetrically related O-H...O and N-H...O hydrogen bonds are generated in the crystal structure. The resulting two-dimensional (001) "double-layered" networks are joined into a three-dimensional network via inversion-related halogen-oxygen interactions.

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RESUMEN

The combination of the pH-metric and NMR studies is used to examine the stabilities and coordination modes as well as related structural aspects of zinc(II), magnesium(II) and calcium(II) complexation to piperyd-1-yl-methane-1,1-diphosphonic acid (1) and its derivatives containing a topologically modified piperidine ring (2-7). The studied compounds coordinate metal ions exclusively via the phosphonate functions with a nitrogen atom remaining protonated over the whole range of studied pH. Compounds 1-6 readily form soluble multinuclear complexes of type [M(3)(HL)(2)] and [M(3)(HL)(3)](3-) with Zn(2+) or [M(2)(H(2)L)(2)] with Ca(2+) and Mg(2+). These species are formed based on dimers consisting of two head-to-head arranged molecules linked by strong symmetrical hydrogen bonds. The placement of the two methyl groups at 2- and 6-positions on the piperidine ring precludes the molecular recognition via similar hydrogen bonds and accounts for different complexation properties of 7 compared to 1-6. The role that the metal coordination plays on conformation dynamics in 1-7 is also discussed.

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RESUMEN

The crystal structures of 3-methylpiperid-1-ylmethane-1,1-diphosphonic (2), 4-methylpiperid-1-ylmethane-1,1-diphosphonic (3), 2-ethylpiperid-1-ylmethane-1,1-diphosphonic (4), and 2-methylpiperid-1-ylmethane-1,1-diphosphonic (5) acids have been determined and are discussed with respect to their molecular organization and crystal-packing preferences. The chair conformation, predominant also in solution, favors equatorial positioning of the bulky substituents of the heterocyclic N and C atoms. The molecular geometry also provides access to intramolecular hydrogen-bond formation between the axial protons located on the nitrogen atoms, as well as the carbon atoms closest to it, and phosphonic/phosphonate oxygen atoms. The molecules preferably arrange in monolayers, observed in all crystals with an exception of 3. The layers are held in place in the third direction through van der Waals interactions. The analysis of two-dimensional hydrogen-bonded networks is concentrated on revealing how the substituent's topology of the molecule affects the solid-state organization in well-defined structures and is aimed at unraveling the consequences and the possible conformational changes by stepwise network disruption upon crystal dissolution in water. The solution NMR studies are focused on revealing the role that the topochemistry of the substituent plays for the stereodynamics in 2-5. It is demonstrated that in contrast to piperid-1-ylmethane-1,1-diphosphonic acid (1), in which the ring inversion/rotation around the C-N bond concerted with the N-H...O hydrogen-bond breaking/formation process leads to a mixture of two interconverting conformers, the concerted N-H...O breaking/rotation/N-H...O formation process in 2 and 3 allows for a predominance of one conformer in solution. However, placement of a substituent at 2-position in the ring hampers the rotation around the C-N bond; this makes 4 and 5 significantly less flexible relative to compounds 1-3. In addition, both compounds 4 and 5 are proved to exist as a mixture of two conformers, the equilibrium of which in acidic solution is shifted towards the conformer found in solid state. In alkaline solutions of 4 and 5, the equilibrium is shifted towards the conformer that is forced by the flipping of the heterocyclic ring. These results correlate well with recently documented differences in the biological potency of this group of compounds.

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