Publications 2008

2008

Multiple hydrogen bonds in the self-assembly of aminotriazine and glutarimide. Decisive role of the triazine substituents

Blanca Manzano, Felix Jalon, M Soriano, Ana Rodriguez, Antonio de la Hoz, Ana Sanchez-Migallon. The self-assembly of 6-R-2,4-diamino-1,3,5-triazines (R = Ph, p-tolyl, piperidino) and glutarimide has given rise to three new complexes.  The triazine:glutarimide ratio depends on the R group (1:1 for Ph, 5, and p-tolyl, 6, and 2:1 for piperidino, 7).  In all cases, a triple hydrogen bond between the triazine and the imide is formed but the 3D structure is clearly different depending on R group.  In complexes 5 and 6, the triazine/glutarimide pairs interact through double hydrogen bonds of the type N-H···O/O···H-N to form dimers.  In the case of 5, each dimer interacts with another four situated in a different plane and a zigzag sheet is formed.  In 6, however, the dimers are almost parallel and planar sheets are thus obtained.  In the case of 7, zigzag sheets are also formed but these consist of triazine/glutarimide units bonded to triazine mols.  Weak interactions (weak hydrogen bonds, C-H···π contacts and hydrophobic contacts) on or between sheets are obsd.  Common trends concerning the 3D structures have been found in these derivs. as well as for other previously described examples.  Restricted rotation around the C-NH2 bond is obsd. at low temp. in soln. – Cryst. Growth Des. (2008) vol. 8 (5) pp. 1585-1594

Una orientación de la Química para el Siglo XXI

Antonio de la Hoz, Ángel Díaz-Ortiz. Química Sostenible. Mapfre Seguridad 2008, 110, 32-42

Anion-Dependent Self-Assembly of Silver(I) and Diaminotriazines to Coordination Polymers: Non-Covalent Bonds and Role Interchange between Silver and Hydrogen Bonds

Blanca Manzano, Felix Jalon, M Soriano, M Carrion, M Carranza, Kurt Mereiter, Ana Rodriguez, Antonio de la Hoz, Ana Sanchez-Migallon. New coordination polymers were obtained by the self-assembly of silver salts AgX (X = BF4, PF6, CF3SO3) and 2,4-diamino-6-R-1,3,5-triazines L (R = Ph and p-tolyl) AgLX (1-6).  A complex of different stoichiometry, [Ag3L2(H2O)(acetone)2](BF4)3, 7 (R = phenyl), also was synthesized.  The three-dimensional structures of five compds. were detd. by x-ray diffraction studies.  For the AgLX complexes, when X = BF4 and R = Ph or p-tolyl, chiral chains with alternating Ag and L are formed.  The chains are cross-linked by the counteranions in a three-dimensional fashion through hydrogen bonds and weak Ag···F interactions giving rise to a structure with solvent-filled channels.  Different and more compact structures were found when the counteranion is CF3SO3 (OTf).  When R = Ph, sheets are formed which consist of [Ag2(OTf)2L2] units with double triflate bridges and which contain columns of π-π stacked arenes.  Hydrogen bonds connect the sheets.  When AgOTf was used and R is p-tolyl, a different and unusual ladderlike structure was obtained in which the rungs are double asym. bridges consisting of the triflate groups bonded to Ag in κ2O,μ2-O and κ1O,μ2-O fashion.  The ladders are parallel to each other and are mutually linked by N-H···N hydrogen bonds to give a 3-dimensional architecture.  A very similar ladderlike structure was found for 7 but with a water mol. and a BF4- group acting as bridges.  The role played by the hydrogen bonds in complex 6 to form the 3-dimensional structure is played in 7 by [Ag(acetone)2] fragments.  The noncovalent interactions play an important role in the different solid-state 3-dimensional structures.  The behavior of the new derivs. in soln. also was analyzed.  A new species was detected at low temps., and this exhibits restricted rotation of the Ph ring. – Inorg. Chem. (Washington, DC, U. S.) (2008) vol. 47 (19) pp. 8957-8971

Photophysical, electrochemical, and mesomorphic properties of a liquid-crystalline [60]fullerene-peralkylated ferrocene dyad

S. Campidelli, David Scanu, Robert Deschenaux, Dragana Milic, Ester Vazquez, Maurizio Prato, Maurizio Carano, Massimo Marcaccio, Francesco Paolucci, G Rahman, Dirk Guldi. Two fullerenea-peralkylated ferrocene derivatives were synthesized: (1) a liquid-crystalline dyad (compound 1) was obtained by introduction of nonamethyl ferrocene into a liquid-crystalline fullerene derivative and (2) a reference compound (compound 2) was synthesized by attachment of nonamethyl ferrocene to a fulleropyrrolidine. The liquid-crystalline dyad displayed an enantiotropic smectic A phase from 57 to 155 A[degree]C. Oxidation and reduction processes were investigated by cyclic voltammetry, and were in agreement with the electrochemical characteristics of the redox-active units (peralkylated ferrocene, fullerene, dendrimer). Photoinduced electron transfer from ferrocene derivative to fullerene was identified. – J. Mater. Chem. (2008) vol. 18 (13) pp. 1504-1509

Dynamic Imaging of Functionalized Multi-Walled Carbon Nanotube Systemic Circulation and Urinary Excretion

L Lacerda, A Soundararajan, R Singh, G Pastorin, K. T Al-Jamal, J Turton, P Frederik, M. A Herrero, S Li, A Bao, D Emfietzoglou, S Mather, W. T Phillips, M Prato, A Bianco, B Goins, K Kostarelos. Intravenously administered multi-walled carbon nanotubes, functionalized with DTPA and radiolabeled with Indium-111, were dynamically tracked in vivo using a microSingle Photon Emission Tomography scanner. Imaging showed that nanotubes enter the systemic blood circulation and within 5 min begin to permeate through the renal glomerular filtration system into the bladder. Adv. Mater. (2008) vol. 20 (2) pp. 225-230

Synthesis of dendrimer–carbon nanotube conjugates

A García, M Herrero, S Frein, R Deschenaux, R Muñoz, I Bustero, F Toma, M Prato. We describe the coupling between Carbon Nanotubes (CNTs) and a second-generation cyanophenyl-based dendrimer. The goal of our work is the synthesis of highly functionalized CNTs without provoking damage to the conjugated π-system. One approach is the attachment of dendrimers with a high density of functional groups to the CNTs. These groups serve as anchor points for further reactions. With this aim, we have carried out a primary modification on CNTs by the use of 1,3 dipolar cycloaddition reaction. We have employed Single Wall Carbon Nanotubes (SWNTs) as well as Multi Wall Carbon Nanotubes (MWNTs) obtaining 238 μmol and 511 μmol of pyrrolidine groups per gram, respectively. The amount of amino groups introduced in the system was measured by the Kaiser test as well as thermogravimetric analyses. As a second step, dendrimer incorporation was performed by carbodiimide chemistry. Thermogravimetric Analysis, Raman Spectroscopy and Atomic Force Microscopy characterization techniques are reported for the characterization of the final CNT–dendrimer conjugate. The results show that the dendrimer has been attached covalently to the previously generated amine groups. Morphologically, the attached dendrimer with an estimated theoretical molecular length of 6.4 nm, generates a wrapping of 8 nm thick around the CNTs walls. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) – phys. stat. sol. (a) (2008) vol. 205 (6) pp. 1402-1407

Advances in the Covalent Functionlization of Carbon Nanotubes M.A. Herrrero, M. Prato, Molecular Crystals and Liquid Crystals, 483, 21-32, 2008

Tissue histology and physiology following intravenous administration of different types of functionalized multiwalled carbon nanotubes

Lara Lacerda, Hanene Ali-Boucetta, Maria Herrero, Giorgia Pastorin, Alberto Bianco, Maurizio Prato, Kostas Kostarelos. The present study addresses the short-term impact (first 24 h) of intravenous administration of various types of multiwalled nanotubes (MWNTs) on the physiology of healthy mice. – Nanomedicine (2008) vol. 3 (2) pp. 149-161

Carbon-Nanotube Shape and Individualization Critical for Renal Excretion

Lara Lacerda, Maria Herrero, Kerrie Venner, Alberto Bianco, Maurizio Prato, Kostas Kostarelos. Two fullerene–peralkylated ferrocene derivatives were synthesized: (1) a liquid-crystalline dyad (compound 1) was obtained by introduction of nonamethyl ferrocene into a liquid-crystalline fullerene derivative and (2) a reference compound (compound 2) was synthesized by attachment of nonamethyl ferrocene to a fulleropyrrolidine. The liquid-crystalline dyad displayed an enantiotropic smectic A phase from 57 to 155 °C. Oxidation and reduction processes were investigated by cyclic voltammetry, and were in agreement with the electrochemical characteristics of the redox-active units (peralkylated ferrocene, fullerene, dendrimer). Photoinduced electron transfer from ferrocene derivative to fullerene was identified. – Small (2008) vol. 4 (8) pp. 1130-1132

Nonthermal Microwave Effects Revisited: On the Importance of Internal Temperature Monitoring and Agitation in Microwave Chemistry

M Herrero, Jennifer Kremsner, C Kappe. The concept of nonthermal microwave effects has received considerable attention in recent years and is the subject of intense debate in the scientific community. Nonthermal microwave effects have been postulated to result from a direct stabilizing interaction of the electric field with specific (polar) molecules in the reaction medium that is not related to a macroscopic temperature effect. In order to probe the existence of nonthermal microwave effects, four synthetic transformations (Diels−Alder cycloaddition, alkylation of triphenylphosphine and 1,2,4-triazole, direct amide bond formation) were reevaluated under both microwave dielectric heating and conventional thermal heating. In all four cases, previous studies have claimed the existence of nonthermal microwave effects in these reactions. Experimentally, significant differences in conversion and/or product distribution comparing the conventionally and microwave-heated experiments performed at the same measured reaction temperature were found. The current reevaluation of these reactions was performed in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using a multiple fiber-optic probe system. Using this technology, the importance of efficient stirring and internal temperature measurement in microwave-heated reactions was made evident. Inefficient agitation leads to temperature gradients within the reaction mixture due to field inhomogeneities in the microwave cavity. Using external infrared temperature sensors in some cases results in significant inaccuracies in the temperature measurement. Applying the fiber-optic probe temperature monitoring device, a critical reevaluation of all four reactions has provided no evidence for the existence of nonthermal microwave effects. Ensuring efficient agitation of the reaction mixture via magnetic stirring, no significant differences in terms of conversion and selectivity between experiments performed under microwave or oil bath conditions at the same internally measured reaction temperatures were experienced. The observed effects were purely thermal and not related to the microwave field. – The Journal of Organic Chemistry (2008) vol. 73 (1) pp. 36-47

Microwave-Induced Multiple Functionalization of Carbon Nanotubes

Fulvio Brunetti, M Herrero, Juan Muñoz, Angel Díaz-Ortiz, Jessica Alfonsi, Moreno Meneghetti, Maurizio Prato, Ester Vázquez. We describe a new synthetic strategy to produce multifunctionalized carbon nanotubes using a combination of two different addition reactions, the 1,3-dipolar cycloaddition of azomethine ylides and the addition of diazonium salts, both via a simple and fast microwave-induced method. The presence of multifunctionality on the SWNTs has been confirmed using the most useful techniques for the characterization of carbon nanotubes. The doubly functionalized SWNTs can be considered potentially useful for many interesting applications. – Journal of the American Chemical Society (2008) vol. 130 (25) pp. 8094-8100

Parasitosis and cancer Miguel Fernández Braña, Yolanda Martín-Cantalejo, Ana S. Migallón, Marina Morán The treatments of neoplastic and parasitary diseases present some common chemical and pharmacological profiles. In this paper, a comparative study between chemical structures of each therapeutic group that have similar functions is shown. The conclusion is that every new chemical with activity in any of these areas is a suitable candidate to be tested in the other one. Anales de la Real Academia Nacional de Farmacia, 2008, 74, 29-50

Supramolecular Interactions at the Picomole Level Studied by 19F NMR Spectroscopy in a Microfluidic Chip

M. Victoria Gómez, David N Reinhoudt, Aldrik H Velders.

19F NMR spectroscopy is performed on nanoliter volumes in a microfluidic chip equipped with a planar microcoil (see picture). The high resolution and sensitivity allow the detection of small chemical shift variations, which enables investigation of the supramolecular interaction between NaPF6 and α-cyclodextrin. – Small (2008) vol. 4 (9) pp. 1293-1295

Selectivity under microwave irradiation. Benzylation of 2-pyridone: an experimental and theoretical study

Antonio de la Hoz, Maria Prieto, Michel Rajzmann, Cozar de, Angel Diaz-Ortiz, Andres Moreno, Fernando Cossio. The reaction of 2-pyridone with benzyl bromide in the absence of base and under solvent-free conditions has been studied exptl. and by computational methods.  This reaction was one of the first reported examples in which modification of selectivity under microwave irradn. was obsd.  C- and/or N-alkylations were obtained depending on the benzyl halide and the heating system.  N-Alkylation through mechanism A (SN2 mechanism) is kinetically favored while C-alkylation through an SN1-type mechanism is thermodynamically favored and is obsd. under microwave irradn.  Two SN1-type mechanisms (mechanisms B and C) have been calcd., mechanism C being a kind of SNi.  The influence of the pyridone/benzyl bromide ratio was studied.  A second mol. of pyridone stabilizes the transition state and assists the leaving of the bromide ion.  The occurrence of C-alkylation under microwave irradn. is explained by the predominance of the thermodn. control in these conditions.  Under microwave irradn. N-alkylation through an SN1-type mechanism (mechanism C) can also occur.  The dependence of the outcome of N-alkylation on the benzyl bromide ratio has been explained by a shift in the mechanism from SN2 to SN1 under microwave irradn.  Computational calcns. have shown to be a useful tool for detn. of the origin of the selectivity under microwave irradn. – Tetrahedron (2008) vol. 64 (35) pp. 8169-8176

 

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