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Comunicaciones Científicas Abiertas
Año 2005
New Potent 5-Substituted Benzofuroxans as Inhibitors of Trypanosoma Cruzi
Growth. Quantitative Structure-Activity Relationship Studies
G. Aguirre1, L. Boiani1 M. Boiani1, H. Cerecetto1, R. Di Maio1, M.
González1, W. Porcal1, A. Denicola2, O. E. Piro3, E. E. Castellano4, M.
Sant'Anna5 & E. J. Barreiro6, Bioorganic & Medicinal Chemistry 13,
6336-6346 (2005)
1) Department of Organic Chemistry, Faculty of Chemistry/Faculty of
Sciences.
2) Department of Physical Biochemistry, Faculty of Sciences, University of
the Republic, 11400-Montevideo, Uruguay.
3) Department of Physic, National University of La Plata, 1900-La Plata,
Argentina
4) Institute of Physic of São Carlos, University of São Paulo,
13560-São Carlos
5) Departamento de Química, ICE, Universidade Federal Rural do Rio de
Janeiro, Seropédica.
6) LASSBIO, Faculty of Pharmacy, University Federal of Río de
Janeiro, Río de Janeiro, Brazil.
Benzofuroxan derivatives have been shown to inhibit growth of Trypanosoma
Cruzi, the etiologic agent of Chagas' disease. In order to develop a
pharmacophoric model for this activity, quantitative structure-activity
relationships for selected benzofuroxans have been studied. In this study some
derivatives were synthesized and in vitro evaluated to complete the set of
compounds. Conventional multiple regression analysis of the substituents'
physicochemical properties provided acceptable QSAR. Moreover, exigencies of
three-dimensional activity were clearly observed from a 3D-QSAR study in terms
of comparative molecular field analysis. In both approaches, 2D- and 3D-QSAR,
it was necessary to include an indicator variable that takes into account the
N-oxide position in the benzofuroxan system. For the new analogues, these
positions were clearly established using low temperature-NMR experiments. The
QSAR-results allow us to insight into the spatial and electronic exigencies to
increase the anti-trypanosomal activity of the studied compounds.
A Preliminary Observation of Additive Thermodynamic Contribution of Pendant
Arms to the Complexation of Calixarene Derivatives with Mercury (II)
A. F. Danil de Namor1, S. Chahine1, E. E. Castellano2, O. E. Piro3 &
H. D. B. Jenkins4, J. Chem. Soc., Chem. Comm. 3844-3846 (2005).
1) Chemistry, School of Biomedical and Molecular Sciences, University of
Surrey, Guildford, GU2 7XH, UK.
2) Instituto de Física de São Carlos, Universidade de
São Paulo, C. P. 369, 13560 São Carlos (SP), Brazil.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP (CONICET - UNLP), C.C. 67, 1900 La
Plata, Argentina.
4) Department of Chemistry, University of Warwick, Coventry, CV4 7Al, United
Kingdom.
An additive thermodynamic contribution of pendant arms to the complexation
of calixarene derivatives with mercury(II) in acetonitrile is for the first
time demonstrated.
Solvent Control on the Selective, Non-selective and Absent Response of a
Partially Substituted Lower Rim Calix(4)arene Derivative for Soft Metal Cations
(Hg(II) and Ag(I)). Structural and Thermodynamic Studies
A. F. Danil de Namor1, S. Chahine1, E. E. Castellano2 & O. E. Piro3,
Journal of Physical Chemistry A 109, 6743-6751 (2005).
1) Laboratory of Thermochemistry, Department of Chemistry, University of
Surrey, Guildford, Surrey GU2 7XH, UK.
2) Instituto de Física de São Carlos, Universidade de
São Paulo, C. P. 369, 13560 São Carlos (SP), Brazil.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP (CONICET - UNLP), C.C. 67, 1900 La
Plata, Argentina.
The solvent control on the ability of a partially substituted lower rim
calix(4)arene derivative,
5,11,17,23,tetra-tert-butyl[25,27-bis(hydroxy)-26,28-bis(ethylthio
ethoxy)]-calix(4)arene, 1, to host soft metal cations (Hg(II) and Ag(I)) is
demonstrated through 1H NMR, electrochemical (conductance measurements) and
thermodynamic characterisation of the complexation process in a wide variety of
solvents. Solvent-ligand interactions were assessed from 1H NMR measurements
involving 1 and various solvents in CDCl3. Thus the formation of a 1:1, 1CH3CN,
adduct is reported. As far as metal cations are concerned, depending on the
medium their complexation of 1 was only observed with Hg(II) and Ag(I). Thus in
acetonitrile 1 is more selective for Hg(II) relative to Ag(I) by a factor of
2.2 × 103. In methanol the selectivity is reversed to an extent that the
affinity of 1 for Ag(I) is 1.4 × 103 higher than that for Hg(II). However,
1 is unable to recognise selectively these cations in N,N-dimethylformamide
while in propylene carbonate the ability of 1 to interact with these cations is
lost. An outstanding feature of thermodynamics emerges when an assessment is
made on the solvent effect on the complexation of these cations and analogous
calix(4)arene derivatives. Thus in acetonitrile the energetics of cation
complexation by the hydrophilic cavity of a calix(4)arene containing mixed
pendant groups is built up from thermodynamic data for the same process
involving derivatives with common functional groups at the narrow rim. This
unique example of additive contribution of pendant arms is for the first time
demonstrated in the field of calixarene thermochemistry. The medium effect on
the thermodynamics of complexation of 1 and soft metal cations is used for the
isolation of Hg1(ClO4)2.2MeCN and Ag21(ClO4)2 complexes. The x-ray structured
of theses complexes are reported. Final conclusions are given.
Chemoselective hydrolysis of the iminic moiety in salicylaldehyde
semicarbazone promoted by ruthenium
M. Vieites1, P. Buccino2 L. Otero1, M. González2, O. E. Piro3, R.
Sánchez Delgado4, M. Sant'Anna5, E. Barreiro5, H. Cerecetto2 & D.
Gambino1, Inorganica Chimica Acta 358(11) 3065-3074 (2005).
1) Cátedra de Química Inorgánica, Facultad de
Química, Universidad de la República, Gral. Flores 2124, C. C.
1157, 11800 Montevideo, Uruguay.
2) Departamento de Química Orgánica, Facultad de
Química - Facultad de Ciencias, Universidad de la República,
Iguá 4225, 11400 Montevideo, Uruguay.
3) Departamento de Física and Instituto IFLP (CONICET), Facultad de
Ciencias Exactas, Universidad Nacional de La Plata, C.C. 67, 1900 La Plata,
Argentina.
4) Centro de Química, Instituto Venezolano de Investigaciones
Científicas (IVIC), Caracas, Venezuela.
5) LASSBio, Laboratório de Avaliação e Síntese
de Substancias Bioativas, Faculdade de Farmácia, Universidade Federal do
Rio de Janeiro, Caixa Postal 68006, Rio de Janeiro, 21944-910, RJ, Brazil
Ortho-Hydroxybenzaldehyde semicarbazone (salicylaldehyde semicarbazone)
undergoes chemo-selective hydrolysis of the iminic carbon nitrogen double bond
through its reaction with [RuCl2(dmso)4] in ethanol in the presence of water,
yielding free salicylaldehyde and semicarbazide that remains coordinated to the
ruthenium ion as a bidentate N,O-donor to afford
[RuCl2(dmso)2(semicarbazide)]·2H2O complex. The ruthenium-semicarbazide
complex has been characterized by 1H-NMR and FTIR spectroscopies and X-ray
diffraction methods. Related semicarbazones, derived from p-hydroxybenzaldehyde
and benzaldehyde, were not hydrolyzed under the same conditions, suggesting a
significant role of the structural o-hydroxy motive in the reaction.
Theoretical studies were performed in order to gain further insight on the
mechanism of reaction. Results support the hypothesis that the ortho hydroxy
moiety, in the keto tautomeric form, participates in the chemo-selective
hydrolysis promoted by [RuCl2(dmso)4].
Step Wise Formation of s-Alkynyl, Vinylidene, and Vinylphosphonium
Complexes of Manganese(I)
J. Ruiz1, R. Quesada1, M. Vivanco1, E. E. Castellano2 & O. E. Piro3
Organometallics 24, 2542-2545 (2005).
1) Departamento de Química Orgánica e Inorgánica,
Facultad de Química, Universidad de Oviedo, 33071 Oviedo, Spain.
2) Instituto de Física de Sao Carlos, Universidade de São
Paulo, C.P.369, 13560 São Carlos (SP), Brazil.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP (CONICET), C.C.67, 1900 La Plata,
Argentina.
Reaction of methyl propiolate with the diphosphino methanide complex [Mn(CO)
4(PPh2)2CH] (1) produces simultaneously the insertion of the alkyne into the
C-H bond, giving [Mn(CO)4(PPh2)2C-C(H)=C(CO2-Me)H] (2), and the deprotonation
of the alkyne mediated by the diphosphino methanide ligand, affording the
?-alkynyl derivative fac-[Mn(C?C-CO2Me)(CO)3(dppm)] (3). Protonation of 3 with
HBF4 at 200K affords the corresponding vinylidene compound
fac-[Mn(C=C(H)-CO2Me)(CO)3(dppm)]BF4 (5), which, on raising the temperature to
243K, undergoes the spontaneous insertion of the vinylidene ligand into a Mn-P
bond.
Synthesis and Biological Properties of New 5-Nitroindazole Derivatives
V. J. Arán1, C. Ochoa1, L. Boiani2, P. Buccino2, H. Cerecetto2,
A. Gerpe2, M. González2, D. Montero3, J. J. Nogal3, A.
Gómez-Barrio3, A. Azqueta4, A. López de Ceráin4, O. E.
Piro5 & E. E. Castellano6, Bioorganic & Medicinal Chemistry 13,
3197-3207 (2005).
1) Instituto de Química Médica (CSIC), Juan de la Cierva, 3,
28006 Madrid, Spain.
2) Dpto. de Química Orgánica, Facultad de Ciencias-Facultad de
Química, UDELAR, Iguá 4225, Montevideo, 11400 Uruguay
3) Dpto. de Parasitología, Facultad de Farmacia, Universidad
Complutense, 28040 Madrid, Spain
4) Centro de Investigación de Farmacobiología Aplicada (CIFA),
Universidad de Navarra, Irunlarrea s/n, 31080 Pamplona, Navarra, Spain
5) Universidad Nacional de La Plata and Instituto IFLP(CONICET),
Departamento de Física, Facultad de Ciencias Exactas, C.C. 67, 1900 La
Plata, Argentina
6) Instituto de Física de São Carlos, Universidade de
São Paulo, C.P. 369, 13560 São Carlos (SP), Brazil
A series of new 3-alkoxy- or
3-hydroxy-1-[?-(dialkylamino)alkyl]-5-nitroindazoles has been synthesized and
their trichomonacidal, antichagasic and antineoplastic properties studied. Five
derivatives (5, 6, 8, 9 and 17) showed remarkable trichomonacidal activity
against Trichomonas vaginalis, at 10 ?g/mL concentration. Three compounds (8,
10, 11) exhibited interesting antichagasic activity and these same compounds
moderate antineoplastic activity against TK-10 and HT-29 cell lines. Unspecific
cytotoxicity against macrophages has also been evaluated and only compounds 9,
10 and 11 resulted cytotoxic at the higher dose evaluated (100 ?g/mL), loosing
cytotoxicity at lower doses. QSAR studies have been carried out.
Solid state 111Cd NMR studies on cadmium(II)-2,x-pyridindicarboxylates.
Crystal structure of triaqua (pyridine-2,4-dicarboxylato)cadmium(II)
hemihydrate: [Cd(II)(2,4-pydc)(H2O)3].1/2H2O
G. Mendoza-Díaz1, G. Rigotti2, O.E. Piro2 & E.E. Sileo3,
Polyhedron 24, (7), 777-783 (2005).
1) Universidad de Guanajuato, Facultad de Química, Noria Alta s/n,
Guanajuato, Gto. 36050 Mexico.
2) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Programa PROFIMO(CONICET), C. C. 67, 1900 La Plata,
Argentina.
3) Departamento de Química Inorgánica, Analítica y
Química Física, Facultad de Ciencias Exactas y Naturales,
Universidad de Buenos Aires, Pabellón II, Ciudad Universitaria,
C1428EHA, Buenos Aires, Argentina.
The synthesis and characterization by solid-state 111Cd- NMR of Cd(2,3-),
Cd(2,4-), Cd(2,5-) and Cd(2,6-pyridinedicarboxylato).xH2O is reported. Results
indicate that the 111Cd-NMR signal is very sensitive to the to the relative
position of both carboxylates. Similar shifts (at 54.0 and 55.4 ppm) are found
for the 2,4- and the 2,6- isomers where carboxylates groups are meta to each
other. For the 2,3- and 2,5- derivatives (carboxylates in orto and meta), the
signals are detected at 119.6 and 84.2 ppm. The crystal and molecular structure
of the seven-coordinated cadmium complex,
[Cd(2,4-pyridinedicarboxylato)(H2O)3]·1/2H2O is also reported. This data
allows a correlation between Cd-O and Cd-N coordination and geometry with 111Cd
chemical shift. The ?iso value encountered for the 2,6-pydc derivative may
indicate an heptacoordinated sphere for the compound. Additional coupling
between 111Cd and 14N in 2,3- (also found in 2,4-pydc) suggests only one N
coordinated to Cd. The anisotropy magnitude, and the asymmetry parametry, is
also analysed.
Palladium(II) complexes of 2-benzoylpyridine-derived thiosemicarbazones:
spectral characterization, structural studies and cytotoxic activity
A. P. Rebolledo, M. Vieites, D. Gambino, O. E. Piro, E. E. Castellano,
C. L. Zani, E. S. Fagundes, L. R. S. Teixeira, A. A. Batista & H. Beraldo,
J. Inorganic Biochemistry 99, 698-706 (2005).
a) Departamento de Química, Universidade Federal de Minas Gerais,
31270-901, Belo Horizonte, MG, Brazil.
b) Cátedra de Química Inorgánica, Facultad de
Química, Universidad de la República, Gral. Flores 2124, C. C.
1157, 11800 Montevideo, Uruguay.
c) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP(CONICET), C.C. 67, 1900 La Plata,
Argentina.
d) Instituto de Física de São Carlos, Universidade de
São Paulo, C.P. 369, 13560 São Carlos (SP), Brazil.
e) Instituto René Rachou, Fundação Oswaldo Cruz
(Fiocruz), 30190-002, Belo Horizonte, MG, Brazil.
f) Departamento de Química, Centro de Ciências Exatas e de
Tecnologia, Universidade Federal de São Carlos, C. P. 676,. 1365-905,
São Carlos (SP), Brazil.
Palladium(II) complexes of 2-benzoylpyridine thiosemicarbazone (H2Bz4DH) and
its N(4)-methyl (H2Bz4M) and N(4)-phenyl (H2Bz4Ph) derivatives were obtained
and fully characterized. [Pd(2Bz4DH)Cl] (1) crystallizes in the monoclinic
space group P21/c with a=11.671(1), b=10.405(1), c=13.124(1) Å,
?=115.60(1) , and Z=4; [Pd(2Bz4M)Cl] (2) in the monoclinic space group P21/c
with a=9.695(1), b=15.044(1), c=10.718(1) Å, ?=105.38(1) , and Z=4 and
[Pd(2Bz4Ph)Cl] (3) in the triclinic space group P-1 with a=9.389(1),
b=13.629(1), c=15.518(1) Å, ?=70.25(1), ?=73.46(1), ?=83.57(1) , and two
independent molecules per asymmetric unit (Z=4). All complexes show a quite
similar planar four fold environment around palladium(II). A negatively charged
organic molecule acts as a tridentate ligand and binds to the metal through the
pyridine nitrogen, the imine nitrogen and the sulfur atom. A chloride ion
occupies the fourth coordination site. The planar complexes stack nearly
parallel to one another in the lattice conforming a layered crystal structure.
The cytotoxic activity of the thiosemicarbazones and their metal complexes was
tested against the MCF-7, TK-10 and UACC-62 human tumor cell lines. The ligands
exhibit lower values of IC50 and LD50 than the complexes, H2Bz4Ph being the
most active with IC50 < 0.003 M; LD50=13.4 M; IC50=9.3 M, LD50=12.9 M;
IC50<0.003, LD50=13.8 M in the MCF-7, TK-10 and UACC-62 cell lines
respectively. Among the complexes, [Pd(2Bz4Ph)Cl] (3) exhibited the lowest
values of IC50 in the three studied cell lines.
Synthesis, crystal structure and spectroscopic characterization of a novel
bis(oxo-bridged) dinuclear vanadium(V)-dipicolinic acid complex
A. C. González-Baró, E. E. Castellano, O. E. Piro & B.
S. Parajón-Costa, Polyhedron 24, 49-55 (2005).
1) Centro de Química Inorgánica (CEQUINOR, CONICET/UNLP),
Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.Correo 962,
1900-La Plata, Argentina.
2) Instituto de Física de São Carlos, Universidade de
São Paulo, C.P. 369, 13560 São Carlos (SP), Brazil.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Institute IFLP (CONICET), C. C. 67, 1900- La Plata,
Argentina.
The reaction of [VO(dipic)(H2O)2].H2O with creatinine in H2O-CH3OH mixture
yields yellow crystals of bis (oxo bridged) binuclear vanadium(V) compound of
stoichiometry [CH3NHC(NH2)2]2 [V2O4(dipic)2], (dipic2-=pyridine 2,6
dicarboxylate; CH3NHC(NH2)2+=methyl guanidinum). The molecular structure of the
compound was determined by X-ray diffraction methods. The binuclear complex
crystallized in the monoclinic space group P21/c with a=9.557(1), b=12.363(1),
c=10.466(1) Å,=101.56 (2)º, and Z=2. It sits at a crystallographic
inversion center with the pair of V(V) atoms in an edge-sharing distorted
octahedral environment. In the [VO2(dipic)]- halves of the dimer, the VO2+
cation is coordinated to a dipicolinate group acting as a tridentate planar
ligand through one oxygen of each carboxylic group and the hetereocyclic
nitrogen atom. The oxo ligand laying near the coordination plane bridges the
dimer through a weak axial bond with the other half. This gives rise to a V=O2
bond length slightly longer than the other, terminal, V=O1 bond. The infrared
and Raman spectra of the compound were recorded and discussed on the basis of
its structural data and by comparison with those of the free acid. The results
are also compared with the corresponding ones of related structures.
Vanadium(V) Complexes with Salicylaldehyde Semicarbazone Derivatives
bearing in vitro Anti-tumor Activity toward Kidney Tumor Cells (TK-10). Crystal
Structure of [VVO2(5-bromosalicylaldehyde semicarbazone)]
P. Noblía1, M. Vieites1, B. Parajón-Costa2, E. J. Baran2,
H. Cerecetto3, P. Draper3, M. González3, O. E. Piro4, E. E. Castellano5,
A. Azqueta6, A. López de Ceráin6, A. Monge-Vega6 & D.
Gambino1, Journal of Inorganic Biochemistry 99, 443-451 (2005).
1) Cátedra de Química Inorgánica, Facultad de
Química, Universidad de la República, Gral. Flores 2124, C. C.
1157, 11800 Montevideo, Uruguay.
2) Centro de Química Inorgánica (CEQUINOR/CONICET-UNLP), C.C.
962 and [d] Departamento de Física and Instituto IFLP (CONICET), C.C.
67, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 1900 La
Plata, Argentina.
3) Departamento de Química Orgánica, Facultad de
Química - Facultad de Ciencias, Universidad de la República,
Iguá 4225, 11400 Montevideo, Uruguay.
4) Instituto de Física de São Carlos, Universidade de
São Paulo, C.P. 369, 13560 São Carlos (SP), Brazil.
5) Unidad en I+D de Medicamentos, CIFA, Universidad de Navarra, Irunlarrea
s/n, 31080 Pamplona, España.
As a contribution to the development of novel vanadium complexes with
pharmacologically interesting moieties, new dioxovanadium(V) semicarbazone
complexes with the formula cis-VO2L, where L=5-bromosalicylaldehyde
semicarbazone and 2-hydroxynaphtalen-1-carboxaldehyde semicarbazone, have been
synthesized. and characterized by 1H- and 13C-NMR, Raman and FTIR
spectroscopies. Results were compared with those previously reported for other
three analogous complexes of this series. The five complexes were tested in
three different human tumor cell lines for bioactivity as potential anti-tumor
agents, showing selective cytotoxicity on TK-10 cell line. Results showed that
structural modifications on the semicarbazone moiety could have a significant
effect on the anti-tumor activity of the vanadium complexes. In addition, the
electrochemical behavior of all the complexes was studied. No apparent
correlation could be demonstrated between reduction potentials of the complexes
and their anti-tumor activities. The molecular structure of the novel
[VVO2(5-bromosalicylaldehyde semicarbazone)] complex was solved by X ray
diffraction methods. The vanadium atom shows a distorted square pyramidal
coordination sphere. The (VO2)+ cation is coordinated to a nearly planar (L)-
anion acting as a tridentate ligand through both oxygen and one nitrogen atoms.
Año 2004
Tautomerism and reactivity in heterocycles N-oxides: a spectroscopic and
theoretical strudy of benzimidazoles N-oxide derivatives
(N-hydroxybenzimidazoles)
M. Boiani1, H. Cerecetto1, M. González1, O. E. Piro2 & E. E.
Castellano3, Journal of Physical Chemistry A, 108, 11241-11248 (2004).
1) Laboratorio de Química Orgánica, Facultad de
Ciencias-Facultad de Química, Universidad de la República,
Igúa 4225, Montevideo 11400, Uruguay.
2) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata e Instituto IFLP (CONICET), C. C. 67, (1900) La Plata,
Argentina.
3) Instituto de Física de São Carlos, Universidad de
São Paulo, C. P. 369, 13560 São Carlos, SP, Brazil.
The tautomeric forms of benzimidazole N-oxide derivatives in solution were
studied using nuclear magnetic resonance (NMR) techniques and density
functional theory (DFT) calculations. In the gas-phase the N-hydroxy tautomer
is more stable than the N-oxide, whereas in solution the stabilization of one
form or the other depends on hydrogen bond formation with the N-hydroxy/N-oxide
moiety. Derivative 4, having a 2-carboxamide moiety, was the only one present
as a mixture of tautomers, being N-oxide the predominant one. This was assigned
to the formation of an internal hydrogen bond between the N-oxide group and the
amide hydrogen atom. The tautomeric form present in the solid state was
conclusively assigned by X-ray diffraction techniques to the N-hydroxy
tautomer. In the crystal a strong O-H…N intermolecular bond gives rise to
supramolecular polymeric chains in the lattice. This strong interaction was
also seen in the infrared spectrum and was assigned to two broad bands at 2367
and 2526 cm-1. The vibrational spectrum was satisfactorily described by DFT
calculations and an example of this is the prediction of the band corresponding
to the N-O stretching (N-oxide) just 1% lower than the experimental value.
Uncorrelated calculations (HF) were not able to give an unambiguous assignation
of this band. The reaction of derivative 1 (Ethyl 5-nitrobenzimidazol-3-oxide
2-carboxylate) against different kinds of electrophiles, hard and soft, led
only to O-substituted products. This result was explained in terms of the HSAB
theory using a local-global approach.
The addition reaction of diamides to 1,2,5-thiadiazole 1,1-dioxide
derivatives
J. A. Caram1, M. V. Mirifico1,2, S. L. Aimone1, O. E. Piro3, E. E.
Castellano4 and E. J. Vasini1, J. Physical Organic Chemistry 17, 1091-1098
(2004).
1) Instituto de Investigaciones Fisicoquímicas Teóricas y
Aplicadas (INIFTA), Facultad de Ciencias Exactas, Departamento de
Química, Universidad Nacional de La Plata, Casilla de Correo 16,
Sucursal 4, (1900) La Plata, Argentina.
2) Facultad de Ingeniería, Departamento de Ingeniería
Química, Universidad Nacional de La Plata, Calle 47 y 1, (1900) La
Plata, Argentina.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and IFLP (CONICET), C. C. 67, 1900 La Plata, Argentina.
4) Instituto Física de São Carlos, Universidade de São
Paulo, C.P. 369, 13560 São Carlos (SP), Brazil.
The reactions of several derivatives of 1,2,5-thiadiazole 1,1-dioxide
(3,4-diphenyl (1a), 3,4-di(p-methoxiphenyl) (1b), phenanthro [9,10-c] (1c) and
acenaphtho [1,2-c]- 1,2,5-thiadiazole 1,1-dioxide (1d),
3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2a) and
4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (2b)), with
reagents possessing two nucleophilic nitrogen atoms (urea, N,N'-dimethylurea,
thiourea, N-methylthiourea, N-ethylthiourea, N-allylthiourea, N, N'-
diethylthiourea, N, N'-diphenylthiourea, dithioxamide and sulfamide), were
followed by cyclic voltammetry (CV) and UV-VIS spectroscopy in aprotic solvents
solution. The products were isolated, characterized by IR, 1H-NMR, 13C-NMR, and
their structure was confirmed by single crystal X-ray diffraction. Several
substrate-nucleophile combinations (1a-d and 2a with some ureas and thioureas)
reacted to give good yields of new compounds formed by the addition reaction of
the two nitrogen atoms of the nucleophile to the two >C=N double bonds of
the 1,2,5-thiadiazole 1,1-dioxide ring. Some systems (1a-dithioxamide and
2b-thiourea) did not react, while in others (e.g. 1a-sulfamide) a monoaddition
equilibrium reaction was observed.
Ethyl p-tert-butyl calix(4)arene ethanoate: the Role of Acetonitrile in the
Extraction of Alkali-Metal Picrates and on the X-ray Structures of the Sodium
Complexes
A. F. Danil de Namor1, M. A. Pugliese2, A. R. Casal2, W. B.
Aparicio-Aragon3, O. E. Piro4 & E. E. Castellano5, Physical Chemistry
Chemical Physics 6, 2004, 3286-3291(2004).
1) Laboratory of Thermochemistry, Chemistry, School of Biomedical and
Molecular Sciences, University of Surrey, Guildford, Surrey GU2 7XH.
2) Laboratorio de Química Analítica, Departamento de
Química, Universidad Nacional del Sur, Bahía Blanca 8000,
Argentina.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de la Plata and Instituto IFLP (CONICET-UNLP), C.C. 67, 1900 La Plata,
Argentina.
4) Instituto de Física de São Carlos, Universidade de
São Paulo, C.P.369, 13560 São Carlos (SP), Brazil.
Distribution data for alkali metal picrates in the water-chloroform solvent
system in the absence and in the presence of acetonitrile were used to
determine the partition constants of the dissociated electrolytes in the
mutually saturated solvents and the ion-pair formation constants in the water
saturated organic phase. These data were compared with those previously
reported in water-benzonitrile and water-dichloromethane solvent systems. The
same experiments carried out in the presence of ethyl p-tert-butylcalix(4)arene
tetraethanoate, EtCalix(4), led to the calculation of distribution and
extraction constants in these solvents systems. The presence of acetonitrile in
the organic phase enhances significantly the extraction constant to an extent
that these are the highest values so far obtained in the solvent systems
investigated. This enhancement in extraction is attributed to metal complex
stabilization promoted by the presence of acetonitrile in the hydrophobic
cavity of the ligand. The X-ray structures of two sodium complexes (picrate as
the counter-ion), isolated from water saturated chloroform with and without
acetonitrile are reported for the first time. In the first complex, the
macro-cycle is sited on a crystallographic four-fold axis and hosts an
acetonitrile solvent molecule in its calix and a sodium ion in its hydrophilic
cavity. The metal is in a eight fold Archimedean square anti-prism environment,
coordinated to the phenol oxygen atom and to the carbonyl oxygen atom of the
four rotationally symmetry related pendant arms. The macro-cycle of the other
complex adopts a slightly distorted cone conformation and its hydrophilic
cavity also hosts a sodium ion. But now the metal is in a seven-fold
environment, coordinated to the four phenol oxygen atoms and to the carbonyl
oxygen atoms of three pendant arms acting as bidentate ligands. The fourth,
mono-dentate, pendant arm points away from the hydrophilic cavity and its
terminal -CH2-CH3 group interacts hydrophobically with the calix of a
neighboring complex giving rise to a supra-molecular polymeric structure in the
lattice.
Thermodynamics of Host-Guest Interactions in Lower Rim Functionalized
Calix[4]arenes and Metal Cations: The Medium Effect
A. F. Danil de Namor1, S. Chahine1, E. E. Castellano2 & O. E. Piro3,
J. Phys. Chem. B,108,11384-11392 (2004).
1) Laboratory of Thermochemistry, Department of Chemistry, University of
Surrey, Guildford, Surrey GU2 7XH, UK.
2) Instituto de Física de São Carlos, Universidade de
São Paulo, C. P. 369, 13560 São Carlos (SP), Brazil.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP (CONICET - UNLP), C.C. 67, 1900 La
Plata, Argentina.
A new calix[4]arene derivative containing mixed pendant arms in its lower
rim,
5,11,17,23-tetra-tert-butyl[25,27-bis(ethylethanoate)oxy-26,28-bis(ethylthioethoxy)]-calix[4]arene,
1, has been synthesised and characterised by 1H and 13C NMR. 1H NMR data
carried out in CDCl3, CD3CN, CD3OD and C3D7NO suggest that as far as
acetonitrile is concerned, the hydrophobic cavity is likely to embrace a
solvent molecule. It is shown that the hosting capacity of 1 towards metal
cations is greater in acetonitrile than in N,N-dimethylformamide and in
methanol. Thus, in the former solvent, complexation with various cations (Li+,
Na+, Ag+, Ca2+, Cu2+, Hg2+ and Pb2+) occurs while in the latter media, 1
interacts only with Ag+ and Hg2+. This statement is corroborated by 1H NMR,
conductance, calorimetric and potentiometric measurements. It is concluded that
through molecular inclusion of acetonitrile in the hydrophobic cavity of 1, the
hydrophilic cavity of the adduct becomes more receptive to host metal cations
than that of the free ligand. In propylene carbonate, the results show that the
ligand loses its ability to interact with metal cations. Thus in acetonitrile,
selective recognition of 1 for Hg2+ is demonstrated to an extent that the
selectivity for this cation is greater by factors of 1.8 × 103, 1.9 ×
103, 6.9 × 103, 1.8 × 104, 4.1 × 104 and 4.5 × 104,
relative to Pb2+, Na+, Li+, Cu2+, Ag+ and Ca2+, respectively. This statement is
supported by the thermodynamic characterization of the complexation process
involving these systems in acetonitrile, N,N-dimethylformamide and in methanol.
Thus, the medium effect on the binding process is carefully assessed. The
results show that replacement of two ester groups in two alternate pendant arms
of the tetraester calix[4]arene derivative by thiomethyl moieties has altered
significantly the binding capacity and the selective behavior of the latter
relative to the former. Final conclusions are given.
Metal-assisted Regio- and Stereospecific Insertion of Alkynes into a C-H
Bond
Leading to Functionalized Diphosphane Ligands
J. Ruiz1, R. Quesada1, V. Riera1, E. E. Castellano2 and O. E. Piro3,
Organometallics 23, 175-177 (2004).
1) Departamento de Química Orgánica e inorgánica,
Facultad de Química, Universidad de Oviedo, 33071 Oviedo, Spain.
2) Instituto de Física de Sao Carlos, Universidade de Sao Paulo,
C.P.369, 13560 Sao Carlos (SP), Brazil.
3) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP (CONICET), C.C.67, 1900 La Plata,
Argentina.
Reaction of the complex fac-[Mn(CNtBu)-CO)3(PPh2)2C-H] (1) with dimethyl
acetylene dicar-boxylate and methylpropiolate affords the compounds
fac-[Mn(CNtBu)(CO)3(PPh2)2CC(R)=C(R)-H] (2a, R=R'=CO2Me; 2b, R=H, R'=CO2Me),as
a result of regio- and stereo specific insertion of the alkynesintothe C-H bond
of the diphosphanyl methanide ligand, allowing highly selective metal-assisted
synthesis of new functionalized diphosphane derivatives.
New Vanadium(V) Complexes with Salicylaldehyde Semicarbazone Derivatives:
Synthesis, Characterization and In Vitro Insulin Mimetic Activity. Crystal
Structure of [VVO2(salicylaldehyde semicarbazone)]
P. Noblía1, D. Gambino1, L. Otero1, E. J. Baran2, P. Draper3, H.
Cerecetto3, M. González3, O. E. Piro4, E. E. Castellano5, T. Inohara6,
Y. Adachi6, and H. Sakurai6, European Journal of Inorganic Chemistry 2004,
322-328.
1) Cátedra de Química Inorgánica, Facultad de
Química, Universidad de la República, Gral. Flores 2124, C. C.
1157, 11800 Montevideo, Uruguay.
2) Centro de Química Inorgánica (CEQUINOR/CONICET), C. C. 962,
Facultad de Ciencias Exactas, Universidad Nacional de La Plata, C.C. 67, 1900
La Plata, Argentina.
3) Departamento de Química Orgánica, Facultad de
Química - Facultad de Ciencias, Universidad de la República,
Iguá 4225, 11400 Montevideo, Uruguay.
4) Departamento de Física and Instituto IFLP (CONICET), Facultad de
Ciencias Exactas, Universidad Nacional de La Plata, C.C. 67, 1900 La Plata,
Argentina.
5) Instituto de Física de São Carlos, Universidade de
São Paulo, C.P. 369, 13560 São Carlos (SP), Brazil.
6) Department of Analytical and Bioinorganic Chemistry, Kyoto Pharmaceutical
University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
A series of new dioxovanadate(V) semicarbazone complexes with the formula
cis-VO2L, where L=salicylaldehyde semicarbazone (L1), N4-n-butyl
salicylaldehyde semicarbazone (L2) or N4-(2-naphtyl) salicylaldehyde
semicarbazone (L3), have been synthesized, characterized by 1H and 13C NMR and
FTIR spectroscopies and tested for bioactivity as potential insulin mimetic
agents. All dioxovanadate(V) complexes exhibited essentially non in vitro
insulin mimetic activity, but VO2L2 complex developed weak activity in the
presence of ascorbic acid. The molecular structure of the novel vanadium
salicylaldehyde semicarbazone complex VO2L1 was solved by X ray diffraction
methods. It crystallizes in the tetragonal space group P42/n with
a=b=12.7674(7), c=11.5308(5)Å, and Z=8. The vanadium atom is in a
distorted square pyramidal coordination, with L1 acting as tridentate ligand
through its azomethynic nitrogen, its carbonyl oxygen and its deprotonated
phenolic oxygen. The coordination sphere is completed with two oxo ligands at
cis positions.
Año 2003
New Rhenium(V) Nitrofuryl Semicarbazone Complexes. Crystal Structure of
[ReOCl2(PPh3)(3-(5-Nitrofuryl)acroleine semicarbazone)]
L. Otero1, P. Noblia1, D. Gambino1, H. Cerecetto2, M. González2,
R. Sánchez-Delgado3, E. E. Castellano4 & O. E. Piro5, Zeitschrift
fuer Anorganische und Allgemeine Chemie 629, 1033-1038 (2003).
1) Cátedra de Química Inorgánica, Facultad de
Química, Universidad de la República, C.C.1157, 11800 Montevideo,
Uruguay.
2) Departamento de Química Orgánica, Facultad de
Química - Facultad de Ciencias, Universidad de la República,
Iguá 4225, 11400 Montevideo, Uruguay.
3) Centro de Química, Instituto Venezolano de Investigaciones
Científicas (IVIC), Apartado 21827, Caracas, 1020-A, Venezuela.
4) Instituto de Física de São Carlos, Universidade de
São Paulo, C.P. 369, 13560 São Carlos (SP), Brazil.
5) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP(CONICET), C.C. 67, 1900 La Plata,
Argentina.
The synthesis and characterization of the first two Re complexes with
semicarbazone ligands is presented. Selected ligands are 5-Nitro-2-furaldehyde
semicarbazone (Nitrofurazone) (L1) and its derivative 3-(5-Nitrofuryl)acroleine
semicarbazone (L2). Complexes of general formula [ReVOCl2(PPh3)L], where L=L1
and L2, were prepared in good yields and high purity by reaction of
[ReVOCl3(PPh3)2] with L in ethanol or methanol solutions. The complexes formula
and molecular structures were supported by elemental analyses and electronic,
FTIR, 1H, 13C and 31P NMR spectroscopies. In addition, the crystal and
molecular structure of [ReVOCl2(PPh3)L2] was determined by X-ray diffraction
methods. [ReOCl2(PPh3)(3-(5-Nitrofuryl)acroleine semicarbazone)] crystallizes
in the space group P-1 with a=11.2334(2), b=11.3040(2), c=12.5040(2)
Å,=81.861(1),=63.555(1),=83.626(1) , and Z=2. The Re(V) ion is in a
distorted octahedral environment, equatorially coordinated to a deprotonated
semicarbazone molecule acting as a bidentate ligand through its carbonylic
oxygen and azomethynic nitrogen atoms, to an oxo ligand and a chlorine atom.
The six-fold coordination is completed by another chlorine atom and a
triphenylphosphine ligand at the axial positions.
Synthesis and characterization of new ruthenium complexes with active
ligands against Chagas´ disease
L. Otero1, P. Noblia1, D. Gambino1, H. Cerecetto2, R. Di Maio2, M.
González2, J. A. Ellena3 & O. E. Piro4, Inorg. Chim. Acta. 344,
85-94 (2003).
1) Cátedra de Química Inorgánica, Facultad de
Química, Universidad de la República, Gral Flores 2124, C.C.
1157, 11800 Montevideo, Uruguay.
2) Departamento de Química Orgánica, Facultad de
Química-Facultad de Ciencias, Universidad de la República, Gral
Flores 2124, C.C.1157, 11800, Montevideo, Uruguay
3) Instituto de Física de Sao Carlos, Universidade de Sao Paulo, C.P.
369, 13560 Sao Carlos (SP), Brazil.
4) Departamento de Física, Facultad de Ciencias Exactas, Universidad
Nacional de La Plata and Instituto IFLP (CONICET), C.C.67, 1900 La Plata,
Argentina.
Chagas' disease, considered incurable, is a major third world parasitosis
that affects millions of people in Latin America. Previous work has shown that
ruthenium clotrimazole complexes are more active against Trypanosoma cruzi,
causative agent of Chagas' disease, than the corresponding free ligand. In this
work, the synthesis and characterization of a series of new Ru(II) complexes
with different anti-trypanosomal active compounds is presented. Complexes of
general formulae [RuIICl(dmso)2L], where dmso=dimethylsulfoxide and
L=5-nitro-2-furaldehyde semicarbazone (L1), N4-n-butyl-5-nitro-2-furaldehyde
semicarbazone (L2) or 3-(5-nitrofuryl) acroleine semicarbazone (L3), were
prepared in good yields by reaction of [RuIICl2(dmso)4] with L in ethanol or
toluene solutions. Complexes were characterized by elemental analyses and
electronic, FTIR, 1H and 13CNMR spectroscopies. Crystal and molecular
structures of [RuCl2(dmso)2L1] and [RuCl2(dmso)2L2] were determined by X-ray
diffraction methods. In both crystals the ruthenium metal atom is in a quite
similar elongated octahedral environment, equatorially coordinated to the
semicarbazone molecule, acting as a bidentate ligand through its azomethynic
nitrogen and carbonylic oxygen atoms. The six fold coordination is completed
with the sulphur atoms of two dimethylsulfoxide ligands at cis-positions and
two chlorine ions at the axial positions. The proposed formula for L3 complex
was supported by FTIR, NMR and theoretical studies. NOE-NMR experiments allowed
to assign L3 spatial distribution in the complex.
A Crystallographic and Vibrational Study of Cs4[Na2(H2O)10](V10O28)
O. E. Piro1, L. E. Varetti2, S. A.
Brandán3 & A. Ben Altabef3, J. Chemical Cryst.
33, 57-63 (2003).
1) Departamento de Física, Facultad de Ciencias Exactas and IFLP
(CONICET), Universidad Nacional de La Plata, C. Correo 67, 1900 La Plata, R.
Argentina.
2) CEQUINOR (UNLP, CONICET), Departamento de Química, Facultad de
Ciencias Exactas, Universidad Nacional de La Plata, C.Correo 962, 1900 La
Plata, R. Argentina.
3) Instituto de Química y Física, Facultad de
Bioquímica, Química y Farmacia, Universidad Nacional de
Tucumán, San Lorenzo 456, 4000 S.M. de Tucumán, R.Argentina.
The title compound crystallizes in the triclinic space group P-1, with
a=8.6161(4), b=10.591(1), c=11.406(1) Å, ?=67.9770(1), ?=86.8750(1),
?=67.7910(1), and Z=1. The structure was refined to R1=0.0413. The decavanadate
anion, V10O286-, and the [Na2(H2O)10]2+ bridged cation are located at inversion
centers. Partial deuteration of the substance indicates that the coordinated
water molecules are strongly asymmetric, forming weak hydrogen bonds with
acceptor oxygen atoms from the decavanadate anion. The infrared and Raman
spectra are dominated by the water and decavanadate anion bands.
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