DNA-modified electrodes (Ⅶ)——Preparation and characterization of DNA-bonded and DNA-adsorbed SAM/Au electrodes

Two kinds of DNA-modified electrodes were prepared by covalent and adsorptive immobilization of DNA onto self-assembled monolayers of 2, 2'-dithiodiethanol on gold electrodes and characterized by cyclic voltammetry, Xray photoelectron spectroscopy and scanning tunneling microscopy. The results suggest that the methods are satisfactory for the immobilization of DNA on electrodes.     

N,N′-methylenedipyridinium Pt(II) and Pt(IV) hybrid salts: synthesis, crystal and molecular structures of [(C5H5N)2CH2] · [PtCl4] and [(C5H5N)2CH2] · [PtCl6]

The highly insoluble organic-inorganic hybrid ionic compounds N,N??-methylenedipyridinium tetrachloroplatinate(II) [(C₅H₅N)₂CH₂] · [PtCl₄] and N,N??-methylenedipyridinium hexachloroplatinate(IV) [(C₅H₅N)₂CH₂] · [PtCl₆] were obtained by the treatment of N,N??-methylenedipyridinium dichloride monohydrate [(C₅H₅N)₂CH₂]Cl₂ · H₂O with K₂[PtCl₄] or (NH₄)₂[PtCl₆], respectively, in an aqueous solution. Both complexes were isolated, purified, characterised by elemental analysis, and their molecular structures were confirmed by powder X-ray diffraction. The crystal structure of both compounds consists of separated discrete dications [(C₅H₅N)₂CH₂]²⁺ and anions [PtCl _n ]^2? (n = 4 or 6). As anticipated, the dications formed a butterfly shape consisting of two pyridine rings bound to the methylene group via their N atoms, while the Pt centre had a square planar geometry in [(C₅H₅N)₂CH₂] · [PtCl₄] and an octahedral coordination in [(C₅H₅N)₂CH₂] · [PtCl₆]. Interestingly, both crystal structures are stabilised by intermolecular C-H??Cl non-standard hydrogen bonds, ??-?? ring interactions between two pyridine rings of adjacent dications, and also by Cl-?? interactions.     

Synthesis and Crystal Structure of Tetraamminelithium-Rubidiumtriselenide, Li(NH3)4RbSe3, and Pentaamminesodium-Rubidiumtriselenide-Ammonia(1/3), Na(NH3)5RbSe3 · 3NH3

Summary. The ammoniates Li(NH₃)₄RbSe₃ and Na(NH₃)₅RbSe₃·3NH₃ were prepared by the reduction of Rb₂Se₅ with lithium or sodium in liquid ammonia. Single crystals were isolated and characterized by X-ray structure analysis using low temperature techniques. Both compounds contain triselenide anions Se₃^2–, which coordinate to rubidium cations forming ¹[RbSe₃]^– or ¹[Rb(NH₃)₂Se₃]^– chains. The chains are separated in the crystal structures by the homoleptic ammine complexes Li(NH₃)₄⁺ and Na(NH₃)₅⁺.     

Preparation, characterization and crystal structure of Na4[Mn(NCS)6]·13H2O

Na₄[Mn(NCS)₆] · 13H₂O was prepared and characterized by chemical analysis, magnetic susceptibility, thermal dehydration reactions, and single crystal X-ray structure analysis. The crystals are triclinic with a=9.310(1)Å, b=9.367(1)Å, c=9.730(2)Å, = 89.89(1)°,=75.33(1)°, =70.72(1)°, space group P¯I.Z=1. The structure is built up from Na(H₂O)₅ S, Na(H₂O)₆, and Mn(NCS)₆, octahedra. All water molecules are coordinated to Na⁺ -ions in terminal as well as bridging fashion. They form O-H···O as well as O-H···S hydrogen bonds.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Preparation and characterization of Ca1 − x Ce x MnO3 perovskite electrodes

The electrochemical properties of Ca_1 − x Ce _x MnO₃ perovskite-type oxide electrode have been investigated by cyclic voltammetry in Na₂SO₄ aqueous solutions with pH 14. The structural and morphological characterizations have also been investigated and the information used to interpret the electrochemical behavior. An estimation of the electrode’s capacitance and roughness factor has been obtained by means of cyclic voltammetry. The specific capacitance and consequently the roughness factor values are affected by the presence of Ce ions in the oxide. These findings are in agreement with the increase of the oxide-specific surface area by the introduction of Ce ion. The open-circuit potential and the voltammetric patterns are dependent on the presence of Ce ion in the electrodes and support that the surface electrochemistry of the perovskite oxide electrodes is governed by the Mn⁴⁺–Mn³⁺ redox couple.     

Crystal growth, structural, thermal, and dielectric characterization of Tutton salt (NH4)2Fe(SO4)2·6H2O crystals

A good quality single crystal of Tutton salt, (NH₄)₂Fe(SO₄)₂·6H₂O, with dimensions 6 × 7 × 3 mm³ was successfully grown by the slow evaporation growth technique at ambient temperature. The grown crystal was subjected to single crystal X-ray diffraction study which confirms that the grown crystal is monoclinic in nature with the space group P2₁/c. Optical absorption spectrum reveals that the grown crystal has good optical transparency in the entire visible region and its energy band gap was determined. The thermal behavior of the grown crystal was investigated by thermogravimetric and differential thermal analysis. The dielectric measurements were carried out to determine the dielectric behavior of the crystal.     

Intramolecular NH···Pt interactions of platinum(II) diimine complexes with phenyl ligands

Pt(pipNC)(2)(phen) [pipNC(-) = 1-(piperidylmethyl)phenyl anion; phen = 1,10-phenanthroline] was prepared by the reaction of cis-Pt(pipNC)(2) with phen. Crystallographic and (1)H NMR data establish that the phen ligand is bidentate, whereas each piperidyl ligand is monodentate and bonded to the platinum at the ortho position of the phenyl group. Acidic conditions allowed for isolation of the salts of diprotonated Pt(pipNHC)(2)(diimine)(2+) adducts (diimine = phen, 2,2'-bipyridine, or 5,5'-ditrifluoromethyl-2,2'-bipyridine). Crystallographic and spectroscopic data for the diprotonated complexes are consistent with H···Pt interactions (2.32-2.51 ?) involving the piperidinium groups, suggesting that the metal center behaves as a Br?nsted base. Metal-to-ligand (diimine) charge-transfer states of Pt(pipNHC)(2)(phen)(2+) in solution are strongly destabilized (>2500 cm(-1)) relative to Pt(pipNC)(2)(phen), in keeping with the notion that NH···Pt interactions effectively reduce the electron density at the metal center. Though N···Pt interactions in Pt(pipNC)(2)(phen) appear to be weaker than those found for outer-sphere two-electron reagents, such as Pt(pip(2)NCN)(tpy)(+) [pip(2)NCN(-) = 1,3-bis(piperidylmethylphenyl anion; tpy = 2,2':6',2'-terpyridine], each of the Pt(pipNC)(2)(diimine) complexes undergoes diimine ligand dissociation to give back cis-Pt(pipNC)(2) and free diimine ligand. Electrochemical measurements on the deprotonated complexes suggest that the piperidyl groups help to stabilize higher oxidation states of the metal center, whereas protonation of the piperidyl groups has a destabilizing influence.     

Preparation and characterization of a novel single crystal of Th(Ⅳ) with cucurbit[6]uril

One single crystal based on Th~(4+) and cucurbit[6]uril(CB6) in nitric acid aqueous solutions was synthesized by slow evaporation method. The single crystal was characterized by elemental analysis,single crystal X-ray diffraction, XRD, FT-IR and TGA. The complexed cation of Th~(4+) is a ten coordinated structure, in which the central thorium ion is coordinated by six monodentate water molecules and two bidentate nitrates. While CB6, as a second-sphere ligand, coordinates with the water molecules of [Th(NO_3)_2(H_2 O)_6]~(2+) through the formation of hydrogen bonding. Two other nitrate ions act as the counter anions. Besides, there are two free water molecules in the crystal system. The formation of the Th~(4+)-CB6 complex can contribute to the study of the coordination of CB6 and the extraction of Th~(4+) in HNO_3 system     

Synthesis and characterization of a one-dimensional polymeric copper(Ⅱ)-tetrathioporphyrazine

The title polymer PCuS4Pz was synthesized by reaction of 2,3-dicyano-5,6-dihydro-1,4-dithiin,pyromellitic dianhydride and urea with cuprous salt in optimized gentle method.The structure and properties of the PCuS4Pz were characterized by elemental analysis,X-ray powder diffraction,IR,UV-Vis,fluorescence and EPR spectra and variable-temperature magnetic susceptibility.The polymer is black sublimable crystallite and the degree of polymerization has been found to be n>4.The PCuS4Pz in H2SO4 exhibits intensive absorption bands at 236,342,656 and 767 nm and intensive fluorescence band at 410 nm or 464 nm under the excitation of the ultraviolet light of a determined wavelength at room temperature.It has been found that the polymer exhibits a weaker antiferromag-netic interaction (J=-2.cm-1,εff=1.68 B.M.) with an apparent spin S<1/2 in the ground state and its conductivity 298K is 1.01×10-5 S-cm-1 at 13.73 MPa.     

Synthesis and spectroscopic characterization of Cu(II) containing chlorocadmiumphosphate Cd(HPO4)Cl·[H3N(CH2)6NH3]0.5 crystals

Chlorocadmiumphosphate Cd(HPO(4))Cl·[H(3)N(CH(2))(6)NH(3)](0.5) crystals containing Cu(II) ions have been successfully synthesized at room temperature by using organic amine 1,6-diamino hexane as a template. The samples are characterized by X-ray powder diffraction, Thermal and spectroscopic studies. These are crystallizes in the monoclinic crystal system with cell dimensions: a=1.7697, b=0.6576, c=1.9026nm and β=106.5°. FT-IR spectrum showed the absorption bands related to PO(4), NH(3)(+) ions and other organic molecule vibrations originated from the templated molecule. The prepared crystals are stable at room temperature and as well as up to around 300°C which were confirmed by thermal analysis. Optical absorption and EPR studies suggest that Cu(II) ion enters in to the lattice as tetragonally distorted octahedral symmetry, for which crystal field and spin-Hamiltonian parameters are calculated. Bonding parameters are suggesting that there exists partial covalent nature between Cu(II) ions and ligands.     

Synthesis and structure of a new compound (NH4)3[{Ta2(NH)3Cl6}Cl], with a novel imido-bridged chain: 1∞[Ta2(NH)3Cl6]2−

A new imido-bridged tantalum compound, (NH₄)₃[{Ta₂(NH)₃Cl₆}Cl], was synthesized from the mixture of TaCl₅, NaNH₂ and NH₄Cl (excess) in a vacuum sealed silica tube at 350–400 °C. Single crystal X-ray diffraction results for the title compound detailed in the orthorhombic space group Cmcm (No. 63); Z=4, a=10.1601(6) Å; b=19.8834(13) Å; and c=7.4362(4) Å. The structure consists of imido-bridged one-dimensional chains with composition [Ta₂(NH)₃Cl₆]²⁻ and running along c. These chains are separated by ammonium and chloride ions. In the present study, NH₄Cl was used to facilitate relatively smooth reaction between TaCl₅ and NaNH₂, which otherwise leads to an exothermic, self-propagating reaction.     

Preparation and characterization of Fe_3O_4/Au composite particles

Colloid gold with different sizes has been widely used in immunoassay and nucleic acid detection mainly because of their properties for immobilization of biomolecules, such as antibodies and oligonucleo-tides, through chemical reactions via active group SH on the biomolecules. Magnetic particles modified with various chemical groups on their surface can not only exhibit good magnetic responsiveness to an external magnetic field but also immobilize biomolecules through these chemical groups. As…     

Determination of cadmium(II) using glassy carbon electrodes modified with cupferron, ß-naphthol, and multiwalled carbon nanotubes

We report on a simple and reliable method for the determination of trace cadmium ion using a glassy carbon electrode (GCE) modified with cupferron, ß-naphthol and MWCNTs. The operational mechanism consists of several steps: first, the ligand cupferron on the modified electrode reacts with Cd²⁺ ion to form a chelate compound. Next, this chelate is adsorbed by the carrier ß-naphthol following the principle of organic co-precipitation. Finally, the coprecipitated complex is detected by the GCE. This scheme is interesting because it combines preconcentration and electrochemical detection. Two linear responses are obtained, one in the concentration range of 5.0?×?10^?11 to 1.6?×?10^?8 M, the other in the range of 1.6?×?10^?8 to 1.42?×?10^?6 M, with a lower detection limit of 1.6?×?10^?11 M. This modified GCE does not suffer from significant interferences by Cu(II), Hg(II), Ag(I), Fe(III), Pb(II), Cr(III), Zn(II), NO^3?, Cl^?, SO ₄ ^2? ions and EDTA. The response of the electrode remained constant for at least 3 weeks of successive operation. The method presented here provides a new way for the simultaneous separation, enrichment, and electrochemical detection of trace cadmium ion.

[Ru(NH3)6](MoO4)Cl·3H2O and [M(NH3)6](ReO4)3·2H2O (M = Ru, Ir). Synthesis and crystal structure

X-ray crystallographic analysis is used to determine the crystal structures of [Ru(NH₃)₆](MoO₄)Cl·3H₂O and [M(NH₃)₆](ReO₄)₃·2H₂O (M = Ru, Ir) complex salts. The features of the fragment packing are studied.     

Copper(I) hexafluorosilicateπ-complexes with allylammonium salts. Synthesis and crystal structure of [CuOOCH·C3H5NH3]2SiF6 and [Cu2Cl3·2C3H5NH3]2SiF6

Two novel copper (I) -complexes containing the SiF ₆ ^2– anion have been synthesized and studied by X-ray structure analysis. The crystals of the first title compound (A) are monoclinic, space group P2₁/b with a=13.039(5), b=10.586(4), c=6.072(2) Å, =100.23(2)°, and Z=2. The crystals of the second title compound (B) are triclinic, space group with a=14.495(5), b=7.633(2), c=6.429(8) Å, =90.67(8), =81.80(8), =94.05(3)°, and Z=1. In structure A, the copper cations and the bridge formiate anions form infinite [Cu(HCOO)]_n spirals, which are cross-linked due to the -interaction between copper and the double bond AA and the strong hydrogen bonds N–H... F(SiF ₆ ^2– ) to form a three-dimensional framework. In structure B, allylammonium similarly acts as a bridge linking the SiF ₆ ^2– and Cu₄Cl ₆ ^2– anions into layers.Lvov State University. Institute of Physical Chemistry, Ukrainian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 141–148, July–August, 1993.Translated by T. Yudanova     

Preparation,spectroscopic and magnetic characterization of Cu(cyclam)M(CN)<Subscript>4</Subscript> complexes exhibiting one-dimensional crystal structures (cyclam = 1,4,8,11-tetraazacyclotetradecane,M = Ni,Pd, Pt)

From the systems Cu(II)–cyclam–[M(CN)₄]^2? (cyclam = 1,4,8,11-tetraazacyclotetradecane; M = Ni, Pd, Pt), three cyanidocomplexes Cu(cyclam)M(CN)₄ [M = Ni (1), Pd (2), Pt (3)] were isolated and characterized by chemical analysis, IR and UV–VIS spectroscopy. The three compounds are isostructural, and their crystal structures are formed by quasi-linear chains exhibiting [–Cu(cyclam)–μ–NC–M(CN)₂–μ–CN–]_n composition. The Cu(II) atoms reside on centres of symmetry and are coordinated in the form of an elongated octahedron with mean equatorial Cu–N bonds of 2.015(12), 2.017(13) and 2.011(11) Å in (1), (2) and (3), respectively, and weakly N-bonded bridging cyanido ligands in the axial positions [2.5321(9) Å in (1), 2.518(2) Å in (2) and 2.549(3) Å in (3)]. Hydrogen bonds of the N–H···N_cyanido···H–N type link neighbouring chains, and a topologically square network of paramagnetic Cu(II) atoms is formed. The magnetic susceptibilities of all three complexes follow the Curie-Weiss law with a weak antiferromagnetic exchange coupling below 5 K.     

Crystal structure,DSC and Raman studies in CH3C6H4NH(CH3)2·SbCl4

The salt para methyl phenyl dimethyl ammonium tetrachloroantimonate (III) crystallizes in the monoclinic system with space group Cc. The unit cell dimensions are: a=13.780(1) Å, b=14.943(2) Å, c=8.192(1) Å, β=113.39(1)°, with Z=4. The structure consists of ammonium cations and polynuclear anions in which distorted SbCl₅ square pyramids sharing a common Cl atom are held together in infinite chains parallel to the c axis. These chains are themselves interconnected by means of the NH⋯Cl hydrogen bonds. Differential scanning calorimetry study was carried out. The Raman of polycrystalline samples have been recorded at different temperatures between 77 and 300 K. A low-temperature phase transition at 230 K of order-disorder type was found.