Simón Hernández-Ortega

Spectral and structural studies of iron(III), cobalt(II,III) and nickel(II) complexes of 2-pyridineformamide N(4)-methylthiosemicarbazone

Abstract Reduction of 2-cyanopyridine by sodium in dry methanol in the presence of N(4)-methylthiosemicarbazide produces 2-pyridineformamide N(4)-methylthiosemicarbazone, HAm4M. Complexes with iron(III), cobalt(II,III) and nickel(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAm4M, [Ni(Am4M)(OAc)], [Fe(Am4M)2]ClO4 and [Co(Am4M)2]ClO4 have been solved. Coordination is via the pyridyl nitrogen, imine nitrogen and thione or thiolato sulfur when coordinating as the neutral and anionic ligand, respectively.

Structural studies of three isomeric forms of heterocyclic N(4)-substituted thiosemicarbazones and two nickel(II) complexes

Abstract Three structural forms have been isolated among four 2-formyl- and 2-acetylpyridine N(4)-substituted thiosemicarbazones reported. 2-Formylpyridine N(4)-methylthiosemicarbazone and 2-acetylpyridine N(4)-ethylthiosemicarbazone both exist as nonhydrogen bonding E isomers. 2-Formylpyridine 3-azabicyclo[3.2.2]nonylthiosemicarbazone crystallies as a hydrogen bondung Z isomer. The yellow 2-acetylpyridine 3-hexamethyleneiminylthiosemicarbazone crystallized with a bifurcated hydrogen bonding arrangement in which the N(3) hydrogen is formally positioned at N(2), making it tautomeric to the other two forms. Structures of four-coordinate nickel(II) complexes containing the monoanions of 2-formylpyridine 3-azabicyclo[3.2.2]nonylthiosemicarbazone and acetylpyrazine 3-hexamethyleneiminylthiosemicarbazone are included.

Synthetic and spectroscopic investigations of N(4)-substituted isatin thiosemicarbazones and their copper(II) complexes

Abstract A series of N(4)-substituted thiosemicarbazones of isatin were synthesized and their copper(II) complexes prepared from copper(II) chloride. X-ray crystal structures of two of the thiosemicarbazones, isatin 3-(hexamethylenimylthiosemicarbazone) and isatin 3-(N(4)-ethylthiosemicarbazone), have been solved and are compared with a previously published structure of isatin 3-(N(4)- p -tolythiosemicarbazone). The coordination chemistry of the copper(II) complexes of these and other isatin thiosemicarbazones is reported and discussed.

BINUCLEAR COPPER (II) COMPLEXES OF 2-HYDROXYACETOPHENONE 4N-SUBSTITUTED THIOSEMICARBAZONES

Abstract Binuclear copper(II) complexes with eight different 2-hydroxyacetophenone 4N-substituted thiosemicarbazones have been prepared and characterized. IR, electronic, 1H NMR and ESR spectra of the complexes, as well as IR, UV and 1H NMR spectra of the thiosemicarbonazones, have been obtained. The crystal structure for the copper(II) complex of 2-hydroxyacetophenone 3-hexamethyleneiminylthiosemicarbazone, [Cu(Aphexim)]2, has been solved and its structural properties are compared to a recently reported nickel(II) complex. Both the thiosemicarbazones and their copper(II) complexes show no growth inhibitory activity against Aspergillus niger, but many have considerable activity against Paecilomyces variotii. Further, there is a relationship between the antifungal activity and the size of the 4N substituent for both the thiosemicarbazones and their copper(II) complexes.

COPPER(II) AND NICKEL(II) COMPLEXES OF 2,3-BUTANEDIONE BIS(N(3)-SUBSTITUTED THIOSEMICARBAZONES)

Abstract Copper(II) and nickel(II) complexes of 2,3-butanedione bis(N(3)-methyl-, bis(N(3)-dimethyl-, bis(pyridyl- and bis(hexamethyleneiminylthiosemicarbazone), (H2Bu3M, H2Bu3DM, H2Bupip and H2Buhexim, respectively) have been prepared and studied spectroscopically. The four thiosemicarbazones have been characterized by their melting points, as well as IR, electronic and NMR (1H, 13C) spectra. The four coordinate copper(II) complexes have been studied by EPR spectroscopy and the copper(II) and nickel(II) complexes by a number of the spectroscopic techniques mentioned above. Upon formation of these complexes, loss of the N(2)H hydrogens occurs and the ligands coordinate to the metal centers as dianionic, tetradentate N2S2 ligands. The crystal structures of H2Bupip and the nickel(II) complex of 2,3-butanedione N3-methyl-phenylthiosemicarbazone, [Ni(Bu3MPh)], have been solved.

Structural and spectral studies of a heterocyclic N(4)-substituted bis(thiosemicarbazone), H22,6Achexim·H2O, its heptacoordinated tin(IV) complex [Bu2Sn(2,6Achexim)], and its binuclear zinc(II) complex [Zn(2,6Achexim)]2

Abstract The multidentate ligand, 2,6-diacetylpyridine bis(3-hexamethyleneiminylthiosemicarbazone) monohydrate, H22,6Achexim·H2O, crystallizes with one thiosemicarbazone moiety in an intramolecular hydrogen bonded, bifurcated E′ form. The other thiosemicarbazone moiety is E and is not involved in intramolecular hydrogen bonding, but is involved in hydrogen bonding with the hydrate water molecule. The dianion (loss of N3a and N3b hydrogens) of H22,6Achexim acts as a pentadentate ligand, 2,6Achexim, in a planar conformation to a central tin(IV) ion, and as a bridging tetradentate ligand with the two thiosemicarbazone moieties of 2,6Achexim coordinating to different zinc atoms. The tin(IV) is heptacoordinate in a distorted pentagonal dipyramidal configuration, with the five SNNNS donor atoms of 2,6Achexim in the pentagonal plane and the two n-butyl groups in the axial positions. The binuclear zinc complex has two equivalent tetrahedral zinc centers, with the pyridyl nitrogens of the two ligands not coordinated.

Naphthoquinone spiroketal with allelochemical activity from the newly discovered endophytic fungus Edenia gomezpompae.

Chemical investigation of the mycelium of Edenia gomezpompae, a newly discovered endophytic fungus isolated from the leaves of Callicarpa acuminata (Verbenaceae) collected from the ecological reserve El Eden, Quintana Roo, Mexico, resulted in the isolation of four naphthoquinone spiroketals, including three new compounds and palmarumycin CP2 (4). We elucidated the structures of the metabolites by extensive NMR spectroscopy studies, including DEPT, COSY, NOESY, HSQC, HMBC, and chiroptical methods. The trivial names proposed for these compounds are preussomerin EG1 (1), preussomerin EG2 (2) and preussomerin EG3 (3). In addition, the X-ray data for 4 were obtained. The bioactivity of the mycelial organic extracts and the pure compounds was tested against three endophytic fungi (Colletotrichum sp., Phomopsis sp., and Guignardia manguifera) isolated from the same plant species (C. acuminata, Verbenaceae) and against four economically important phytopathogenic microorganisms (two fungoid oomycetes, Phythophtora capsici and Phythophtora parasitica, and the fungi Fusarium oxysporum and Alternaria solani). Spiroketals 1-3 displayed significant growth inhibition against all the phytopathogens. IC50 values for the four phytopathogens were from 20 to 170 microg/ml. Palmarumycin CP2 (4) was not bioactive against any of the fungi tested. Compound 1 showed the strongest bioactivity. The acetylated derivatives of preussomerin EG1 (1), 1a and 1b, were obtained and their biological activity was tested on endophytes and phytopathogens. Preussomerin EG1 1, 1a and 1b exhibited significant bioactivity against all microorganisms tested with the exception of Alternaria solani. This is the first report of allelochemicals with antifungal activity from the newly discovered endophytic fungus E. gomezpompae.

Copper(II) and nickel(II) complexes of 5-methyl-2-hydroxyacetophenone N(4)-substituted thiosemicarbazones

Abstract Mononuclear and binuclear copper(II) and nickel(II) complexes with 5-methyl-2-hydroxyacetophenone N(4)-substituted thiosemicarbazones have been prepared and characterized. IR and 1H NMR spectra of the N(4)-substituted thiosemicarbazones and their metal complexes, as well as ESR spectra of the mononuclear copper(II) complexes, have been obtained. The crystal structures of 5-methyl-2-hydroxyacetophenone N(4)-dimethylthiosemicarbazone and a representative binuclear copper(II) complex have been acquired, and their structural features are compared to related thiosemicarbazones and previously reported binuclear copper(II) thiosemicarbazone complexes.

Trypanocidal constituents in plants: 7. Mammea-type coumarins

Calophyllum brasiliense and Mammea americana (Clusiaceae) are two trees from the tropical rain forests of the American continent. A previous screening showed high trypanocidal activity in the extracts of these species. Several mammea-type coumarins, triterpenoids and biflavonoids were isolated from the leaves of C. brasiliense. Mammea A/AA was obtained from the fruit peels of M. americana. These compounds were tested in vitro against epimastigotes and trypomastigotes of Trypanosoma cruzi, the etiologic agent of Chagas disease. The most potent compounds were mammea A/BA, A/BB, A/AA, A/BD and B/BA, with MC100 values in the range of 15 to 90 microg/ml. Coumarins with a cyclized gamma,gamma-dimethylallyl substituent on C-6, such as mammea B/BA, cyclo F + B/BB cyclo F, and isomammeigin, showed MC100 values > 200 microg/ml. Several active coumarins were also tested against normal human lymphocytes in vitro, which showed that mammea A/AA and A/BA were not toxic. Other compounds from C. brasiliense, such as the triterpenoids, friedelin, canophyllol, the biflavonoid amentoflavone, and protocatechuic and shikimic acids, were inactive against the epimastigotes. The isopropylidenedioxy derivative of shikimic acid was inactive, and its structure was confirmed by X-ray diffraction. Our results suggest that mammea-type coumarins could be a valuable source of trypanocidal compounds.

Synthesis, spectroscopic characterization and crystal and molecular structure of tetrakis(carbonyl)(tetraphenyldithioimidodiphosphinato) manganese(I), Mn(CO)4[(SPPh2)2N]

Abstract Mn(CO) 4 [(SPPh 2 ) 2 N] was prepared by allowing [Mn(CO) 5 ]Br to react with K[SPPh 2 ) 2 N], in THF. The compound was characterized by IR, mass and NMR ( 1 H, 13 C, 31 P) spectroscopy, and its crystal and molecular structure was determined by single-crystal X-ray diffraction. The lattice contains two independent, monomeric molecules, ( 1 ) and ( 1a ). The metal atom has a distorted octahedral coordination geometry (C ax MnC ax 175.9(3)° in ( 1 ), 176.9(3)° in ( 1a )), with two carbonyl groups and the two sulfur atoms of the symmetric monometallic bidentate (mean PS 2.021(2) A in ( 1 ), 2.020(2) A in ( 1a )) dithio ligand unit in equatorial positions (mean MnS 2.420(2), MnC eq 1.804(4), MnC ax 1.855(5) A in ( 1 ), MnS 2.417(2), MnC eq (2) MnC ax 1.862(5) A in ( 1a )). The main difference between the two independent molecules is the conformation of the inorganic MnS 2 P 2 N chelate ring.