Nataša Bukovec

Synthesis, crystal structure, and characterization of three novel compounds of the quinolone family member (norfloxacin)

The synthesis of three novel compounds of norfloxacin (nf) is reported. Their crystal structures are presented and discussed. The first compound, (nfH2)Cl2. H2O (nfH2 = doubly protonated molecule of nf), crystallizes in the monoclinic space group P 21/c with a = 8.438(2), b = 14.281(3), c = 15.012(3) A, β = 93.87(3)°, Z = 4. The carbonyl oxygen O(1) is protonated, and this proton is bonded via intramolecular hydrogen bond to the oxygen O(11) of the carboxylic group (O(11) … O(1) = 2.605(4) A). The terminal nitrogen atom N(24) the piperazine group is also protonated. The positive charge of the nf molecule is neutralized by two chloride anions. The crystal structure is stabilized by numerous hydrogen bonds of the type OH … O, OH … Cl, NH … Cl. The compounds (nfH2)(nfH)[CuCl4]Cl.H2O and (nfH2)(nfH)[ZnCl4]Cl.H2O (nfH = monoprotonated molecule of nf) are isostructural and both crystallize in P 21/c. Both structures are ionic consisting of a tetrachlorometalate (II) anion and two nonequivalent, protonated nf molecules. It seems that in strongly acidic media, the proton is bonded between O(1) and carboxylic oxygen, which prevents the coordination of the metal ions to this position. The results of other measurements (TG, FT-IR, Raman spectroscopy) are also included.

Synthesis, characterization, and crystal structure of a copper(II) complex with quinolone family member (ciprofloxacin): bis(1)-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-piperazin-1ylquinoline-3-carboxylate) copper(II) chloride hexahydrate

The synthesis of the coordination compound [Cu(CF)2]Cl2.6H2O is reported. Its crystal structure is presented and discussed. The title compound crystallizes in the triclinic space group P1 with a = 9.369(2), b = 9.573(2), c = 11.206(2) A, α = 87.37(2), β = 80.58(2), γ = 86.25(2)°, Z = 988.8 A3 Z = 1, and Dc = 1.520 gcm−3. A structure determination, using three-dimensional MoKα x-ray data, resulted in conventional R and Rw values of 0.0399 and 0.0988, respectively, for 3495 unique reflexions for which I > 2σ(I). Refinement was based on F2. The copper atom at the center of inversion is surrounded in a plane by four oxygens (two of the carboxylate groups, two of the carbonyl groups), the corresponding CuO distances are 1.928(2) and 1.931(2) A, respectively. The two chlorine atoms are axially coordinated to Cu at larger distances than 2.688(2) A. The Cl atoms appeared to be disordered over three positions. The nearly planar moieties of Cu(CF)2 are packed parallel in the unit cell interconnected via hydrogen bonds of the type NH⋯O, OH⋯Cl and OH⋯O. The results of other physical measurements (TG, FT-IR, and various analyses) are also included.

Complex formation between some metals and a quinolone family member (ciprofloxacin)

Abstract Some metal [Ca(II), Co(II), Ni(II), Cu(II), Zn(II), Al(III) and Fe(III)] complexes of the quinolone family member (ciprofloxacin = cf) were studied by potentiometric and spectroscopic methods in solution. The results of EPR and polarographic methods are also included. The titration curves for the metal ion-ciprofloxacin were evaluated by assuming all possible models. It was found that a lot of protonated complexes are formed before precipitation in the systems studied. The UV-vis results in the Cu(II)-cf system showed that in the more acidic region a 1:1 complex is favoured, whereas a 1:2 complex prevailed at higher pH values. The coordination of the second ligand is somewhat more favoured than that of the first ligand, and it seems probable that the 1:1 complex is more distorted. Some ternary complexes [Cu(II)-cf-2,2′-bipyridyl, -glycine and -tyrosine] were studied as well. From the ΔlogK value, it was deduced that the formation of the mixed ligand complex in the system Cu(II)-cf-2,2′-bipyridyl is favoured due to back-coordination.

SYNTHESIS, CRYSTAL STRUCTURE, AND CHARACTERIZATION OF TWO METAL-QUINOLONE COMPOUNDS

Two novel metal-quinolone compounds have been synthesized and characterized by analytical, spectroscopic, and X-ray diffraction methods. The crystal structure of both, (erxH2) [FeCl4]Cl and (kinoH2)[CuCl4]. H2O, is presented and discussed (erxH2 = doubly protonated form of enrofloxacin, kinoH2 = doubly protonated form of the second quinolone). In both compounds, the hydrogen atom is bonded between the 4-keto oxygen O(1) and carboxylic oxygen O(11), thus preventing the bonding of the metal to this part of the molecule. Antimicrobial activities of metal-quinolone compounds were tested against different microorganisms.

CeO2 thin films obtained by sol–gel deposition and annealed in air or argon

Abstract Thin films of CeO 2 were prepared on SnO 2 /F-coated glass plates by the sol–gel dip-coating process using CeCl 3 ·7H 2 O as a precursor. The films were heat-treated in an air or argon atmosphere. The structural, electrochemical and optical properties of these films depend on the preparation conditions. Transmission electron microscopy (TEM) showed the films to be polycrystalline with randomly orientated crystallised domains of up to 10 nm in size. The degree of crystallinity of films heat-treated in argon is higher than that of those heat-treated in air, and therefore their charge capacity values (15.9 mC cm −2 after 100 cycles) and reversibility of the ion-storage process (0.99 after 100 cycles) are higher than for films heat-treated in air (10.5 mC cm −2 and 0.86 after 100 cycles, respectively). Both films are optically passive under Li + ion insertion and have high optical transmittance (>80%).

Polymorphism and stability of norfloxacin, (1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinil)-3-quinolinocarboxylic acid

Norfloxacin was studied by thermal methods (TG and DSC), X-ray powder diffraction, and by FT-IR, UV-VIS and NMR spectroscopy. The drug substance can be prepared in two different crystalline forms and in amorphous state, depending on the experimental conditions of preparation. DSC examinations were carried out at various heating rates and by cycling the samples in the temperature range 50°–250°C. The unstable crystalline form undergoes two irreversible solid-solid phase transitions at 176.5° and 197.6°C. The polymorph melts in the temperature range 218.5°–220.0°C.ZusammenfassungNorfloxacin wurde mittels thermischer Methoden (TG und DSC), weiterhin mittels der Debye-Scherrer-Methode und FTIR-, UV-VIS-und NMR-Spektroskopie untersucht. Je nach den experimentellen Bedingungen bei der Herstellung kann die Wirkstoffsubstanz in zwei verschiedenen kristallinen und in einer amorphen Form hergestellt werden. Die DSC-Untersuchungen wurden bei zahlreichen Aufheizgeschwindigkeiten und durch abwechselnden Temperaturwechsel zwischen Raum- und Schmelztemperatur durchgeführt. Die unstabile kristalline Form unterliegt zwei irreversiblen Feststoff-Feststoff-Umwandlungen bei 176.5° und bei 195.6°C. Das polymorphe Material schmilzt im Temperaturbereich 218.5°–220.0°C.

Synthesis and structure of diaquadichlorobis {9-[(2-hydroxyethoxy)methyl]guanine} copper(II)

Abstract A compound with the title [Cu(C8H11N5O3)2(Cl)2(H2O)2] has been prepared from an aqueous solution of CuCl2 and 9-[(2-hydroxyethoxy)methyl]guanine, acyclovir. The crystal structure has been determined by x-ray diffraction. The compound crystallizes in the monoclinic space group C2/c with a = 19.416(2), b = 10.086(1), c = 13.524(2) A, β = 111.17(1)°, V = 2469.67 A3, Z = 4. Least-squares refinement of the structure based on 2775 observations led to an R factor of 0.038. The structure consists of distorted octahedral molecules with Cl ligands and H2O ligands in trans positions [Cu-Cl 2.883(1) and Cu-O(W) 1.983(2) A]. The 9-[(2-hydroxyethoxy)methyl]guanine is trans linked to Cu through N(7) [2.029(2) A]. The side chain is partially folded. A short intramolecular hydrogen bond between O(6) and O(Wl) [2.594 A] significantly lowers the carbonyl stretching frequency [1715 to 1657 cm−1] in the FT-IR spectrum.

Synthesis and Structural Characterisation of a New Form of Bis(acyclovir)(ethylenediamine)platinum(II) − Correlation between the Puckering of the Carrier Ligand and the Canting of the Nucleobases

A new conformer of the [Pt(en)(acv)2]2+ cation (en = ethylenediamine; acv = acyclovir = 9-[(2-hydroxyethoxy)methyl]guanine) has been prepared by slow crystallisation of the [Pt(en)(acv)2]SO4·2.5H2O salt. X-ray diffraction studies have shown that the guanine moieties have a Head-to-Head conformation (HH) with the two C(8)-H vectors pointing towards the same side with respect to the platinum coordination plane; the dihedral angles formed by the purine planes and the coordination plane are 58.3(2)° and 41.5(2)°, respectively. There is a correlation between the canting of the purine bases (right or left handed) and the puckering of the ethylenediamine chelate ring (δ or λ). Right-handed canting is associated with λ puckering of the chelate ring and left-handed canting with δ puckering of the chelate ring, so that in both cases one of the two purines forms an O(6)···H−N hydrogen bond with a “quasi equatorial” NH of the ethylenediamine. The “quasi equatorial” character of the NH appears to be a common feature for intramolecular H-bonds between guanine bases and cis-amines. The purine not involved in the H-bond has the six-membered ring portion leaning towards the cis purine rather than towards the cis amine and may give rise to a weak O(6)···Pt attractive interaction. Such an interaction is supported by density functional (DFT) molecular orbital calculations carried out on the model systems [Pt(NH3)4(CH2O)]2+ and Head-to-Tailcis-[Pt(NH3)2{N(=CH2)−C(=CH2)−C(=O)−NH2}2]2+. The exocyclic chains linked to N(9) each have two different orientations, and all four are stretched away from the metal centre as well as from the purine N(1)H and N(2)H2 protons. The acv and the en NH protons are instead involved in H-bonds with the sulfate anion.

Thermal analysis of nickel oxide films

Nickel oxide films were prepared by chemical deposition on glass substrates using nickel sulphate and potassium persulphate in ammonia solution. Coatings dried in air and at 85°C were characterized by thermal analysis (TG and DTG), FT-IR spectroscopy and X-ray diffraction. The films could be formulated as hydrated forms of 4Ni(OH)2·NiOOH and Ni3O2(OH)4 respectively. The coatings lost water and oxygen on heating to give NiO.ZusammenfassungDünnschichten aus Nickeloxid wurden durch chemische Abscheidung auf Glassubstraten mittels Nickelsulfat und Kaliumpersulfat in Ammoniaklösung hergestellt. Die in Luft und bei 85°C getrockneten Beschichtungen wurden dann mittels TG und DTG, FT-IR-Spektroskopie und Röntgendiffraktion charakterisiert. Diese Dünnschichten können als hydratierte Formen von 4Ni(OH)2NiOOH und Ni3O2(OH)4 beschrieben werden. Beim Erhitzen verlieren diese Beschichtungen Wasser und bilden NiO.

Pt(II) complexes with N-(3-pyridyl)-2-(4-(trifluoromethyl)phenyl)diazenecarboxamide and their reactions with glutathione

The reaction between [PtCl(dmso)(en)]Cl (dmso=dimethyl sulfoxide, en=ethylenediamine) and N-(3-pyridyl)-2-(4-(trifluoromethyl)phenyl)diazenecarboxamide (L) was studied using multinuclear NMR spectroscopy. The water-soluble complexes [PtCl(en)(L-N1)](+) (1) and [Pt(en)(L-N1)(2)](2+) (2) were isolated and their reactions with glutathione (GSH) were investigated to assess the oxidation properties of coordinated L. Both species 1 and 2 oxidized GSH to GSSG, while the reduced form of L (semicarbazide, SL) remained coordinated to Pt(2+). In complex 1 the labile chloride ion was substituted by the thiol moiety of GSH, which gave rise to the release of en in excess GSH over a period of 7 days. Complexes [PtCl(dmso)(en)]Cl, 1, 2 and ligand L were tested against T24 bladder carcinoma cells. Ligand L and complexes 1 and 2 showed higher cytotoxicity than [PtCl(dmso)(en)]Cl.