Petre Ionita

University of Bucharest, București, Bucureşti, Romania

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Publications (76)134.89 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A number of ten stable free mono-, di- and tri-radicals of the TEMPO nitroxide type were synthesized and characterized via physico-chemical methods (elemental analysis, MS, UV-Vis, IR, ESR, and X-ray, where appropriate). The design of the compounds was chosen such that supramolecular interaction could be gained via hydrogen-bonding or π–π interactions; therefore the compounds should contain amino- or urea-moieties, (nitro)aromatic rings, or a crown ether residue. The formation of inclusion complexes between these (poly)radicals and cucurbit[6]uril was studied via Electron Spin Resonance (ESR) spectroscopy. The binding constants were evaluated from the analysis of the rotational correlation time dependence on the concentration of cucurbit[6]uril. These constants are an order of magnitude lower than the values reported before for complexes of TEMPO derivatives with β-cyclodextrin. The complexation behaviour of cucurbit[6]uril was revealed in the ESR spectra of the nitroxides in the presence and in the absence of the host molecules, recorded at low temperatures. The experiments revealed that the mobilities of the nitroxides investigated are higher in the absence of the host molecule, a different behaviour compared with complexes with cyclodextrins. This behavior can be understood by taking into account the role played by the presence of salts necessary to ensure the solubility of cucurbit[6]uril in water.
    No preview · Article · Nov 2015 · New Journal of Chemistry
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    ABSTRACT: Various primary and secondary alcohols were selectively oxidized to the corresponding aldehydes and ketones using silica supported TEMPO as a heterogeneous catalyst and nitrosonium tetrafluoroborate as a cocatalyst. No over-oxidation of aldehydes to acids, nitration processes or oxidation of double bonds was observed. The reported procedure is very convenient, and uses mild experimental conditions (room temperature and dioxygen as the terminal oxidant). Furthermore, the reactions proceeded cleanly and the isolation of the desired compounds required minimal work-up. A mechanistic pathway has been proposed, in which nitrogen oxides and oxoammonium ions act as an electron transfer double bridge.
    No preview · Article · Oct 2015 · Tetrahedron Letters
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    ABSTRACT: TEMPO stable free radical has been supported on porous silica nanoparticles in different ways and the resulted materials have been tested as heterogeneous oxidation catalyst of three benzylic alcohols using air as final oxidant and nitrosonium tetrafluoroborate as cocatalyst. Good to excellent yields were obtained. The catalytic system consists in fact in two coupled cycles, NO/NO2 and TEMPO+/TEMPO, able to convert under mild conditions (room temperature, air, metal and halogen free condition) alcohols into aldehydes or ketones. Under these conditions, supported TEMPO on silica nanoparticles containing gold clusters lowers the efficiency of the catalyst.
    No preview · Article · Sep 2015 · Journal of Porous Materials
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    ABSTRACT: We describe herein the synthesis of 2-alkynylbenzoxazole and 2-alkynylbenzothiazole derivatives through the Sonogashira cross-coupling reaction of the corresponding thioethers and terminal alkynes under aerobic conditions, using CuI and Pd(dppf)Cl2 as catalysts. The synthetic methodology allows the convenient cross-coupling of heteroaromatic substrates with a wide variety of aromatic and aliphatic alkynes, in moderate to good yields. The behavior of mercapto benzoxazoles and benzothiazoles were also investigated in the desulfitative Sonogashira cross-coupling reaction. It is noteworthy that the reaction occurred better under aerobic conditions rather than an inert atmosphere, although with increased amounts of the diyne side-product.
    No preview · Article · Aug 2015 · Tetrahedron Letters
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    ABSTRACT: Silver azide is a primary high explosive that can be initiated by different means. In this work, silver azide nanoparticles were obtained, embedded into silica, and further derivatized with biotin. TEM, DLS, and IR measurements were used to characterize the hybrid energetic nanoparticles. The hybrid nanoparticles are made from an explosive core (silver azide) and a shell (silica), to which has been attached through an organic linker a biological target vectot (biotin).These hybrid nanoparticles can be used as models to study smart energetic nano-materials. © 2015, Kauno Technologijos Universitetas. All rights reserved.
    No preview · Article · Jul 2015 · Materials Science
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    ABSTRACT: This study reports the synthesis of silver nanoparticles (Ag NPs) by the sodium borohydride reduction method and their embedding in a silica shell functionalized with several antibiotics (ampicillin, penicillin G and isoniazide). The characterization of the novel materials was made by UV-visible absorption spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, dynamic light scattering and thermal analysis. TEM micrographs revealed the formation of spherical nanoparticles with size ranging between 20 and 50 nm. The Ag NPs embedded in the silica network exhibited a good antimicrobial efficiency, comparable or even superior to that of antibiotic-containing formulations. This is the first report regarding the synergic antimicrobial effect of Ag NPs embedded in silica and ampicillin, both against planktonic cells and biofilms formed by P. aeruginosa and S. aureus, two of the most fearful resistant bugs. These results are demonstrating the great potential of these nanocomposites to be used in developing novel antimicrobial agents or improving the existent ones, by increasing their efficiency, extending their spectrum of activity and decreasing the probability to select resistance, by simultaneously targeting multiple targets in the microbial cells.
    No preview · Article · Jul 2015 · Journal of Inorganic and Organometallic Polymers and Materials
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    ABSTRACT: The rosemary extract was encapsulated in polyethylene or in covalently-based network gels. The covalent gels were obtained by the reaction of isocyanate end-capped polyethylene glycol (PEG) with β-cyclodextrin or glycerol. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to evaluate the antioxidant activity (AA) of rosemary extract entrapped in polymeric structures and in ethanol or water solutions. The AA of the rosemary extract was determined using a DPPH radical for samples prepared in ethanol, and a water-soluble derivative, the sulphonated DPPH radical (DPPH-SO3Na), for the rosemary extract in water. Formulation of the rosemary extract in polymeric gels ensures a rapid release which determines the AA values similar to those in solution.
    Full-text · Article · Jun 2015 · Chemical Papers
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    ABSTRACT: Low-molecular-weight organic gelators generate physical gels by the formation of three-dimensional fibrous network structures as a response to various physicochemical stimuli such as heat, light, ultrasound and chemical environments. Dibenzylidene sorbitol (DBS) represents a typical compound able to generate gels because of some prerequisite structural features: the presence of functional groups to form intermolecular hydrogen bonds and of aromatic groups to be involved in π-π interactions, or chirality. Herein, we present the synthesis of three derivatives of DBS-bearing carboxy groups attached to phenyl rings and the corresponding spin-labelled compounds. We studied the formation of physical gels resulting from self-assembly of DBS derivatives with the aim of highlighting the influence of the position of the carboxy group on the gel properties. These types of compounds can form gels in polar solvents (such as water, DMSO) by either temperature treatment or variation of the pH. In this study, the systems were investigated by rheological measurements, SEM analysis and EPR measurements. The results showed that the introduction of carboxy groups into the structure of DBS generates weaker gels compared with the parent gelator, DBS. The spin probes used in this study (spin-labelled DBS derivatives and 5-doxyl stearic acid) demonstrated that assembly of gelator molecules is a highly selective process. The two-component feature of EPR spectra of spin probes in gels is proof that EPR spectroscopy is sensitive to the non-homogeneity of these systems.
    No preview · Article · May 2015 · Applied Magnetic Resonance
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    ABSTRACT: The paper describes a rapid and simple method for preparing silver nanoparticles coated with tunable silica shell thickness and their further functionalization with vitamins. Monodispersed silver nanoparticles (Ag NPs) with a mean particle size of 10 nm were prepared by chemical reduction. Silica coating was carried out using the Stober method, by mixing the as prepared silver nanoparticles with tetramethoxysilane and 3-aminopropyltrimethoxysilane. These core-shell nanoparticles were further functionalized with B vitamins in order to facilitate their rapid functionalization to a wide range of end applications. Characterization of the newly synthesized materials was made by UV-visible absorption spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS) and thermal analysis (TG). Their antibacterial activity against Gram-positive and Gram-negative bacterial strains was investigated and the results of our study showed that the linked vitamins on silver nanoparticles coated with silica lead to an increased antimicrobial activity at lower concentrations against planktonic bacterial cells and microbial biofilms. The present study can be useful for future development of different types of biological active materials.
    No preview · Article · Apr 2015 · Ceramics International
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    ABSTRACT: A series of several new isoniazid derivatives, isonicotinic acid 2-(2-hydroxy-8-substituted-tricyclo[7.3.1.02.7]tridec-13-ylidene)-hydrazides, were synthesized and fully characterized. These new isoniazid derivatives were studied regarding their antibacterial activity and cytotoxicity, as well as their influences on some metabolizing enzymes. The best anti-mycobacterial activity was observed in the case of compounds containing alkyl side chains in the 8 position of tricyclo[7.3.1.02.7]tridec-13-ylidene group. On contrary, the antimicrobial activity of these new compounds against various non-tuberculosis strains showed the best activity to be with the phenyl side chain of compound 6. It proved also to be the most toxic, inducing apoptosis and blocking the cell cycle in G0/G1 phase. The cell cycle was blocked in G0/G1 phase also by compound 3, but this compound did not show any toxicity. All compounds induced the expression of NAT1 and NAT2 genes in HT-29 cell line, and the expression of CYP1A1 in HT-29 and HCT-8 cell lines. The expression level of CYP3A4 was increased by compounds 1, 6 and 7 in HCT-8 cells. These results indicated that the activation of other metabolizing pathways, apart from those of isoniazid, take place. It might also point out the possibility of an increased isoniazid acetylation ratio by co-administration with new compounds in slow acetylators.
    No preview · Article · Dec 2014 · Bioorganic & Medicinal Chemistry
  • A.-M. Ariciu · G. Ionita · P. Ionita
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    ABSTRACT: Tobacco smoking represents a source of exposure of humans to the reactive radicals which are considered responsible for chronic diseases. In this work we present the evidence of reactive radicals formation in tobacco smoke using the electron paramagnetic resonance (EPR) spin-trapping method. Four types of commercially available cigarette were used. In each case the cigarette was smoked a quarter, half and totally, and the smoke was passed through a filter into a toluene solutions of the spin traps α-phenyl-N-tbutylnitrone (PBN) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The analysis of the spin-adducts spectra evidenced the formation of different free radicals with short lives (C•, CO•, O• and HO•). The ratio between these radical species depends on the cigarette characteristics (tar and nicotine) and the cigarette length consumption. It was found that the cigarette tar gives also an EPR signal, corresponding to quinone type radicals.
    No preview · Article · Sep 2014 · Revue Roumaine de Chimie
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    ABSTRACT: The degradation of methylparaben (MeP) in water was investigated using a pulsed corona discharge generated in oxygen, above the liquid. A comparison was made between results obtained in semi-batch corona (SBC) configuration (stationary solution, continuous gas flow) and results obtained in a semi-batch corona with recirculation combined with ozonation (SBCR + O3), where the liquid is continuously circulated between a solution reservoir and the plasma reactor and the effluent gas containing ozone is bubbled through the solution in the reservoir. It was found that MeP was completely degraded after 10–15 min of treatment in both configurations. Oxidation by ozone alone, in the absence of plasma, was a slower process. The energy efficiency for MeP removal (Y MeP) and for mineralization (Y TOC) was significantly higher in the SBCR + O3 configuration (Y MeP = 7.1 g/kWh at 90 % MeP removal and Y TOC = 0.41 g/kWh at 50 % total organic carbon (TOC) removal) than in the SBC configuration (Y MeP = 0.6 g/kWh at 90 % MeP removal and Y TOC = 0.11 g/kWh at 50 % TOC removal).
    Full-text · Article · May 2014 · Environmental Science and Pollution Research
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    ABSTRACT: The efficiency of low and medium hydrophobic alcohols as mobile phase additives for lipophilicity determination of parabens was investigated using reversed-phase liquid chromatography and C18 chromatographic column as stationary phase. The eluting strength was evaluated by methylene selectivity determination for different mobile phases, containing water (0.1% H3PO4)-hydrophobic alcohols mixtures, starting with methanol and continued with methanol with 1% upper alcohols (differing through one methylene group, from ethanol to octanol) as organic additive. A good linear dependence (R 2 > 0.99) was observed between the retention factors (log k) and the organic content of the mobile phase in all cases. Several methodologies such as arithmetic mean computation of experimental retention values, extrapolation to zero methanol concentration procedure, and principal component analysis were applied to retention data values in order to determine relevant parameters [mlog k - mean of experimental retention values log k, log kw – extrapolated capacity factor to 100% water, and respectively PC1/log k (scores corresponding to the first principal component)]. The evaluation of the experimental lipophilicity parameters revealed a significant correlation with the reference octanol–water partition coefficients (log Kow) and also with various computed lipophilicity parameters (log P).
    No preview · Article · Apr 2014 · Journal of Liquid Chromatography & Related Technologies
  • Petre Ionita
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    ABSTRACT: Starting from the commercially available silica supported TEMPO and gaseous nitrogen dioxide, a heterogeneous catalyst was obtained and characterized; this is able to convert under mild and clean conditions alcohols into aldehydes and ketones, using molecular oxygen as the final oxidant. A mechanistic pathway is proposed, in which silica supported TEMPO acts as a scavenger and a generator for nitrogen dioxide.
    No preview · Article · Oct 2013 · RSC Advances
  • A. Paun · I. Zarafu · M.T. Caproiu · P. Ionita
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    ABSTRACT: Starting from ready available compounds, a stable diradical of imino-nitroxide type has been synthesized in a multistep process. Structural characterization of the intermediates and final product included 1H- and 13C-NMR, elemental analysis, IR, UV-Vis and EPR spectroscopy. The stable diradical contains also a betaine structure with extended conjugation, which is responsible for its intense colour. Reduction of the stable betaine diradical led to a colour change from blue to yellow. The process is reversible, oxidation restoring the betaine diradical.
    No preview · Article · Aug 2013
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    ABSTRACT: The aim of the study was to synthesize some new compounds with potential anti-tuberculosis activity, containing isoniazid and α,β-unsaturated thiocinnamamide-like thioamides as precursors. The obtained derivatives were evaluated regarding their biological activity (antioxidant and antibacterial), as well as their influence on the eukaryotic cell cycle. The results suggested that the newly obtained derivatives of isoniazid exhibited different biological activities, depending on their structure; thus, the most active compound in terms of anti-oxidant and anti-Mycobacterium tuberculosis effects proved to be the isonicotinic acid N'-(1-amino-1-mercapto-3-phenyl-propen-1-yl)-hydrazide. This compound also increased the expression of NAT1 and NAT2 genes, which are implicated in the metabolism of the isoniazid, demonstrating that it could be rapidly metabolized, and thus well tolerated. The largest spectrum of antibacterial activity (excluding M. tuberculosis) was noticed for the isonicotinic acid N'-[1-amino-1-mercapto-3-(p-chloro-phenyl)-propen-1-yl]-hydrazide, which was also the most cytotoxic, especially at high concentrations, although not significantly affecting the cellular cycle phases. The obtained results showed that the new derivatives could represent potential candidates for the treatment of M. tuberculosis infections, but further research is needed in order to improve their pharmacological properties, by increasing their antimicrobial activity and reducing the risk of side-effects.
    No preview · Article · Jun 2013 · Bioorganic & medicinal chemistry
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    ABSTRACT: Starting from benzocaine, a well-known anaesthetic, ten derivatives were synthesized and characterized by UV–vis, IR, NMR, and elemental analysis. Most of the compounds contain residues with recognized biological activity, like nicotinic acid (vitamin B3 or PP), biotin (vitamin B7 or H), lipoic acid (thioctic acid), adamantine, as well as other residues of crown-ether type, benzofurazane, naphtylurea, di- and tri-nitrobenzene, and a nitroxide radical. The biological evaluation of the obtained compounds included hydrophobicity (lipophobicity) assay, total antioxidant and microbiological activity tests.
    Full-text · Article · May 2013 · Comptes Rendus Chimie
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    ABSTRACT: A thermal analysis study has been performed for the stable free radical 2,2-diphenyl-1-picrylhydrazyl and other ten free radical congeners, together with their corresponding parent hydrazines. Qualitative studies on the decomposition products showed that nitrogen dioxide plays a key role. A mechanistic decomposition pathway is also proposed.
    No preview · Article · Apr 2013 · Journal of Thermal Analysis and Calorimetry
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    ABSTRACT: Silver nanoparticles are prepared by a chemical reduction method, using silver nitrate as the metal precursor and sodium borohydride as the reducing agent. Polyvinylpyrrolidone and 1,2-dimethoxy-ethane are used as stabilizing ligands on the surface nanoparticles. The silver nanoparticles obtained with this method are shown to exhibit typical surface plasmon absorption behavior at about 400 nm, and transmission electron microscopy and dynamic light scattering show that the average size of silver nanoparticles is between 30–50 nm, depending on the chemical procedure and the stabilizer used. The effect of hydrogen peroxide as the oxidant and hydrazine as the reducing agent is studied in conjunction with methylene blue dye. It is demonstrated that the chemical surface modification has great influence on silver nanoparticle reactivity.
    Full-text · Article · Jan 2013 · Digest Journal of Nanomaterials and Biostructures
  • Petre Ionita
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    ABSTRACT: A simple and rapid colorimetric chemosensor for the detection of several nitro-explosives is presented. The method is based on the oxidation of colorless ABTS to its intense blue–green colored radical cation ABTS+ by nitrogen dioxide, which can be generated from nitro-explosives by one of the following two methods: (i) digestion of very small amounts of explosives with alkali hydroxide, yielding nitrite anions, which in acidic medium generate nitrogen dioxide, or (ii) by thermal decomposition of nitro-explosives, which generates directly nitrogen dioxide. In these processes nitrogen dioxide acts as a catalytic intermediate, thus enhancing the detection.
    No preview · Article · Dec 2012 · Tetrahedron Letters

Publication Stats

926 Citations
134.89 Total Impact Points

Institutions

  • 2009-2015
    • University of Bucharest
      • • Department of Organic Chemistry, Biochemistry and Catalysis
      • • Department of Inorganic Chemistry
      București, Bucureşti, Romania
  • 2002-2015
    • Romanian Academy
      • Institute of Physical Chemistry "Ilie Murgulescu"
      Bucureşti, Romania
  • 2010
    • Texas A&M University - Galveston
      Galveston, Texas, United States
  • 2008
    • Institute of Physical Chemistry
      Bucureşti, Bucureşti, Romania
  • 2000-2008
    • The University of York
      • Department of Chemistry
      York, England, United Kingdom
  • 2005-2007
    • CUNY Graduate Center
      New York, New York, United States
  • 1999
    • University of Pitesti
      Piteshti, Argeş, Romania