Preparation of I2@SWNTs: synthesis and spectroscopic characterization of I2-loaded SWNTs

X-ray photoelectron spectroscopy (XPS) along with inductively coupled plasma analysis (ICP-AE) and Raman spectroscopy have been used to define the location and to quantify the amount of iodine in HiPco SWNT samples loaded with molecular I(2) via sublimation (I(2)-SWNTs). The exterior-adsorbed I(2) can be removed (as I(-)) by reducing the sample of filled nanotubes with Na(0)/THF or by heating the I(2)-SWNTs to 300 degrees C (without reduction), leaving I(2) contained only within the interior of the SWNTs (I(2)@SWNTs) as proven by XPS. These I(2)@SWNTs contain approximately 25 wt % of I(2) and are stable without the loss of I(2) even after exposure to additional reduction with Na(0)/THF or upon heating to ca. 500 degrees C.     

Synthesis and crystal and molecular structure of μ-oxo-bis[trifluoroacetato(p-tolyl)iodine]

Crystal and molecular structure of μ-oxo-bis[trifluoroacetato(p-tolyl)iodine] (I) synthesized by a new procedure was determined by X-ray diffraction analysis. Crystals I are orthorhombic, unstable, space group Pbcn, a=17.684(3), b=8.453(3), c=30.560(4) Å, Z=8. The structure of I was solved by direct and Fourier methods and refined by the full-matrix least-squares procedure in an anisotropic-isotropic approximation to R=0.098 (CAD-4 automatic diffractometer, λCuK_α, 1200 observed reflections with I≥2σ). In molecule I, two iodine atoms have T-configuration of valence bonds with the average bond angles O?I?O 169(1) and O?I?C 86(2)°, average bond lengths I?O_μ 2.009(9), I?O_acet 2.269(9), and I?C_aryl 2.11(1) Å, and the bond angle I?O?I 118.1(5)°. In molecule I, two p-Tol substituents are directed to approximately the same side of the medium plane of the central O?I?O?I?O fragment. Crystal structure I has I...O type intra-and intermolecular nonvalent interactions (secondary bonds).     

Two- and three-body photodissociation dynamics of diiodobromide (I2Br-) anion

The photodissociation of gas-phase I(2)Br(-) was investigated using fast beam photofragment translational spectroscopy. Anions were photodissociated from 300 to 270 nm (4.13-4.59 eV) and the recoiling photofragments were detected in coincidence by a time- and position-sensitive detector. Both two- and three-body channels were observed throughout the energy range probed. Analysis of the two-body dissociation showed evidence for four distinct channels: Br(-) + I(2), I(-) + IBr, Br+I(2) (-), and I + IBr(-). In three-body dissociation, Br((2)P(3∕2)) + I((2)P(3∕2)) + I(-) and Br(-) + I((2)P(3∕2)) + I((2)P(3∕2)) were produced primarily from a concerted decay mechanism. A sequential decay mechanism was also observed and attributed to Br(-)((1)S)+I(2)(B(3)Π(0u) (+)) followed by predissociation of I(2)(B).     

A selective chemosensor for detection of Ag(I) and Cu(I) based on an acenaphthoquinone derivative and its complexes

A new Schiff base, acenaphthoquinone bis(diphenylmethlenehydrazone) (L), was synthesized and employed as a chemosensor for detecting Ag(I) and Cu(I). Experimental results showed that the chemosensor exhibited high selectivity and sensitivity. The sensitivity of the chemosensor for Ag(I) or Cu(I) was not affected by other metal ions, such as Ni(II), Nd(III), Zn(II), Fe(III), Cu(II), Na(I), La(III), K(I), and Co(II). Complexes 1 and 2 were synthesized by coordination of L with Ag(I) and Cu(I), respectively. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. They had the same space group P2₁/c. Based on theoretical calculation, mechanism of the chemosensor detecting Ag(I) and Cu(I) was suggested.     

Study on the reaction of triple helix poly(A:2I) with Cu~(2+)

The effect of Cu2+ on the triple-stranded helical structure of poly(A:2I) was studied by means of circular dichroism spectral method with the help of ultraviolet spectral and ethidium bromide fluorescence probe methods. It was found that Cu2+ destabilizes the structure of the triple helix poly(A:2I) and induces its structural transformations, meanwhile, the transformations can be partially reversed by a higher NaCl concentration. The structural transformations may be expressed by the following scheme: poly(A:2I) - poly(A:I) + poly(I)- poly(A) + 2poly(I)     

Versatile and iodine atom-economic co-iodination of alkenes

Molecular iodine, I(2), is readily converted into 2 equiv of acetyl hypoiodite (CH(3)CO(2)I) via oxidation by (diacetoxyiodo)benzene (DAIB) followed by trapping of the iodide ion by acetoxyphenyl iodonium ion formed. The in situ generated CH(3)CO(2)I is utilized for the synthesis of 1,2-iodo-cofunctionalized derivatives of a variety of alkenes. Conversion of both iodine atoms of I(2) to I(+) sources results in 100% iodine atom economy for the reported iodo-cofunctionalization of alkenes.     

Effect of iodine addition on solid-state electrolyte LiI/3-hydroxypropionitrile (1:4) for dye-sensitized solar cells

It was observed that the ionic conductivity of the solid-state electrolyte LiI/3-hydroxypropionitrile (HPN) = 1:4 (molar ratio) decreased dramatically with increasing iodine (I(2)) concentration, which differs from the conduction behavior of the Grotthuss transport mechanism observed in liquid or gel electrolytes. The short-circuit photocurrent density (J(sc)) of the dye-sensitized solar cell (DSSC) based on this electrolyte system increases with increasing I(2) concentration until LiI/I(2) is 1:0.05 (molar ratio). Beyond this limitation, the J(sc) decreases. At low I(2) concentrations (I(2)/LiI < or = 0.05), the J(sc) is mainly affected by the diffusion of I(3)(-). An increase of the I(2) concentration leads to the enhancement of the diffusion of I(3)(-) and an increase of the J(sc). At high I(2) concentrations (I(2)/LiI > 0.05), the factors, including the increased light absorption by the I(3)(-), the increased recombination of electrons at the photoanode with I(3)(-), and the reduced ionic conductivity of the electrolyte, lead to a decrease of J(sc). At the same time, the open-circuit voltage (V(oc)) of the DSSC decreases monotonically with the ratio of I(2)/LiI due to increased dark current in the DSSC. The increased absorption of visible light by the electrolyte, the enhanced dark current, and the reduced ionic conductivity of the electrolyte contribute to the performance variation of the corresponding solid-state DSSC with increasing I(2) concentration.     

Do aurophilic interactions compete against hydrogen bonds? Experimental evidence and rationalization based on ab initio calculations

[M(C6F5)(N(H)=CPh2)] (M = Ag (1) and Au (2)) complexes have been synthesized and characterized by X-ray diffraction analysis. Complex 1 shows a ladder-type structure in which two [Ag(C6F5)(N(H)=CPh2)] units are linked by a Ag(I)-Ag(I) interaction in an antiparallel disposition. The dimeric units are associated through hydrogen bonds of the type N-H...F(ortho). On the other hand, gold(I) complex 2 displays discrete dimers also in an antiparallel conformation in which both Au(I)-Au(I) interactions and N-H.F(ortho) hydrogen bonds appear within the dimeric units. The features of these coexisting interactions have been theoretically studied by ab initio calculations based on four different model systems in order to analyze them separately. The interactions have been analyzed at HF and MP2 levels of theory showing that, in this case, even at larger distances. The Au(I)-Au(I) interaction is stronger than Ag(I)-Ag(I) and that N-H.F hydrogen bonding and Au(I)-Au(I) contacts have a similar strength in the same molecule, which permits a competition between these two structural motifs giving rise to different structural arrangements.     

Spin-orbit ab initio investigation of the ultraviolet photolysis of diiodomethane.

The UV photodissociation (<5 eV) of diiodomethane (CH(2)I(2)) is investigated by spin-orbit ab initio calculations. The experimentally observed photodissociation channels in the gas and condensed phases are clearly assigned by multi-state second-order multiconfigurational perturbation theory in conjunction with spin-orbit interaction through complete active space-state interaction potential energy curves. The calculated results indicate that the fast dissociations of the first two singlet states of CH(2)I(2) and CH(2)I--I lead to geminate-radical products, CH(2)I (.)+I((2)P(3/2)) or CH(2)I (.)+ I*((2)P(1/2)). The recombination process from CH(2)I--I to CH(2)I(2) is explained by an isomerization process and a secondary photodissociation reaction of CH(2)I--I. Finally, the study reveals that spin-orbits effects are significant in the quantitative analysis of the electronic spectrum of the CH(2)I--I species.     

Redox-adaptable copper hosts. Pyridazine-linked cryptands accommodate copper in a range of redox States

A series of structurally characterized copper complexes of two pyridazine-spaced cryptands in redox states + (I,I), (II,I), (II), (II,II) are reported. The hexaimine cryptand L(I) [formed by the 2 + 3 condensation of 3,6-diformylpyridazine with tris(2-aminoethyl)amine (tren)] is able to accommodate two non-stereochemically demanding copper(I) ions, resulting in [Cu(I)(2)L(I)](BF(4))(2) 1, or one stereochemically demanding copper(II) ion, resulting in [Cu(II)L(I)()](BF(4))(2) 3. Complex 3 crystallizes in two forms, 3a and 3b, with differing copper(II) ion coordination geometries. Addition of copper(I) to the monometallic complex 3 results in the mixed-valence complex [Cu(I)Cu(II)L(I)](X)(3) (X = PF(6)(-), 2a; X = BF(4)(-), 2b) which is well stabilized within this cryptand as indicated by electrochemical studies (K(com) = 2.1 x 10(11)). The structurally characterized, octaamine cryptand L(A), prepared by sodium borohydride reduction of L(I), is more flexible than L(I) and can accommodate two stereochemically demanding copper(II) ions, generating the dicopper(II) cryptate [Cu(II)(2)L(A)](BF(4))(4) 4. Electrochemical studies indicate that L(A) stabilizes the copper(II) oxidation state more effectively than L(I); no copper redox state lower than II,II has been isolated in the solid state using this ligand.     

Silver (I) antimicrobial cotton nonwovens and printcloth

In this paper we discuss the preparation and comparative evaluation of silver (I) [Ag(I)] nonwoven and woven antimicrobial barrier fabrics generated from commercial calcium‐sodium alginates and laboratory prepared sodium carboxymethyl (CM) cotton nonwovens and CM‐cotton printcloth for potential use as wound dressings. Degrees of CM substitution (DS) in cotton nonwoven and printcloth samples by titrimetry were 0.38 and 0.10, respectively. Coordination of Ag(I) with carboxylates on fabrics was effected by ion exchange and nitrates were removed by washing to mitigate nitrate ion toxicity issues. Durability of silver coordinated fabrics was tested by soaking them in deionized water with slight agitation at 50°C. Ag(I) alginates and nonwoven Ag(I)‐CM‐cottons lost structural integrity in water. Ag‐CM‐cotton printcloth samples retained structural integrity even after four soak‐and‐dry cycles, were smooth to the touch when dry, and were smoother when moistened. They could be easily peeled from wound surfaces without inducing trauma. Solid‐state carbon‐13 (¹³C) nuclear magnetic resonance (NMR) spectrometry was used to observe changes in carbonyl resonances in Ag(I) alginates and Ag(I)‐CM‐printcloth, and the chemical shift positions of carbonyl resonances of uncoordinated and Ag(I) coordinated fabrics did not change. Inductively coupled plasma‐mass spectrometry (ICP‐MS) was used following fabric digestion to determine the total Ag(I) ion content in fabrics. Ag(I) alginates were found to hold about 10–50 mg Ag(I) per gram fabric; and Ag(I) cotton woven and nonwoven fabrics held about 5–10 mg Ag(I) ions per gram fabric. Kinetic release of Ag(I) after soaking once in physiological saline was studied with ICP‐MS to estimate the availability of Ag(I) upon a single exchange with Na(I) ions on wound surfaces. Alginates released between ～13 and 28% of coordinated Ag(I), and CM‐cotton nonwovens and CM‐cotton printcloth released ～14 and 3% of coordinated Ag(I) ions, respectively. Finally, Ag(I) alginates and Ag(I)‐CM‐cotton printcloth samples were evaluated against Gram‐positive Staphylococcus aureus and Gram‐negative Klebsiella pneumoniae. Ag(I) alginates suppressed 99.95% of bacterial growth in vitro. Even after four soak‐and‐dry cycles in deionized water Ag(I)‐CM‐cotton printcloth suppressed 99.99% of bacterial growth in vitro. Published in 2007 by John Wiley & Sons, Ltd.     

Infrared spectrum of the I- -D2 anion complex

The infrared spectrum of the I(-)-D(2) anion complex is measured in the D(2) stretch region by monitoring production of I(-) photofragments. The rotationally resolved spectrum consists of two overlapping Sigma-Sigma subbands, redshifted by approximately 58 cm(-1) from the free D(2) fundamental vibrational band. These subbands are associated with absorptions by I(-)-D(2) complexes containing ortho and para forms of D(2). The measured rotational constants are consistent with a 3.79 A separation between I(-) and the D(2) center of mass, contracting by 0.08 A when the D(2) subunit is vibrationally excited. Spectroscopic data are used to generate effective radial potential energy curves describing the interaction of ortho and para D(2) with I(-) from which the dissociation energies of I(-)-D(2)(ortho) and I(-)-D(2)(para) are estimated as D(0)=236 and 297 cm(-1), respectively.     

Photocontrol of micellar catalysis

A photoresponsive surfactant with a cationic azobenzene head group (I) was synthesized. It was demonstrated that by mixing (I) with a conventional cationic micelle the rate of the micelle-catalyzed reaction (base-catalyzed proton abstraction from benzoin) can be controlled by light. The origin of the photocontrol was accounted for by the difference in the partitioning of trans-(I) and cis-(I) in the micelle phase.     

Gas-phase collisional relaxation of the CH2I radical after UV photolysis of CH2I2

Transient UV absorption spectra and kinetics of the CH(2)I radical in the gas phase have been investigated at 313 K. Following laser photolysis of 1-3 mbar CH(2)I(2) at 308 nm, transient spectra in the wavelength range 330-390 nm were measured at delay times between 60 ns and a few microseconds. The change of the absorption spectra at early times was attributed to vibrational cooling of highly excited CH(2)I radicals by collisional energy transfer to CH(2)I(2) molecules. From transient absorption decays measured at specific wavelengths, time-dependent concentrations of vibrationally "hot" and "cold" CH(2)I and CH(2)I(2) were extracted by kinetic modeling. In addition, the transient absorption spectrum of CH(2)I radicals between 330 and 400 nm was reconstructed from the simulated concentration-time profiles. The evolution of the absorption spectra of CH(2)I radicals and CH(2)I(2) due to collisional energy transfer was simulated in the framework of a modified Sulzer-Wieland model. Additional master equation simulations for the collisional deactivation of CH(2)I by CH(2)I(2) yield DeltaE values in reasonable agreement with earlier direct studies on the collisional relaxation of other systems. In addition, the simulations show that the shape of the vibrational population distribution of the hot CH(2)I radicals has no influence on the measured UV absorption signals. The implications of our results with respect to spectral assignments in recent ultrafast spectrokinetic studies of the photolysis of CH(2)I(2) in dense fluids are discussed.     

常温常压下β沸石改性吸附剂脱除噻吩类硫的研究

在合成不同硅铝比Naβ沸石的基础上，采用固相离子交换方法制备了Cu(I)、Ag(I)离子改性的β沸石系列吸附剂。样品的结晶度和BET比表面积有所降低，XRD表征结果表明，所制备的样品保持了结构的完整性，随着硅铝比的增加，Naβ样品的BET比表面积增加。Cu(I)、Ag(I)离子的引入使样品的红外骨架振动峰向低波数移动，与相同硅铝比的Naβ沸石相比，吸附剂的BET比表面积有所降低。对模型油的静态吸附结果表明,硅铝摩尔比为25时Cu(I)β吸附性能最好，模型油中硫的质量分数降到10×10－6以下，脱除率达到95％，Ag(I)β次之，脱除率达到87％。常温常压下固定床动态吸附穿透实验得到Cu(I)β、Ag(I)β的穿透硫容分别为0.144mmol/g和0.132mmol/g。     

Ultraviolet photodissociation of the van der Waals dimer (CH3I)2 revisited. II. Pathways giving rise to neutral molecular iodine

The formation of neutral I2 by the photodissociation of the methyl iodide dimer, (CH3I)2, excited within the A band at 249.5 nm is evaluated using velocity map imaging. In previous work [J. Chem. Phys. 122, 204301 (2005)], we showed that the formation of I2+ from photodissociation of the methyl iodide dimer takes place via ionic channels (through the formation of (CH3I)2+). It is thus not possible to detect neutral I2 by monitoring I2+. Neutral I2 is detected in this study by monitoring I atoms arising from the photodissociation of I2. Iodine atoms from I2 photodissociation have a characteristic kinetic energy and angular anisotropy, which is registered using velocity map imaging. We use a two-color probe scheme involving the photodissociation of nascent I2 at 499 nm, which gives rise to I atoms that are ionized by (2+1) resonance enhanced multiphoton ionization at 304.67 nm. Our estimate of the yield of nascent I2 is based on the comparison with the signal from I2 at a known concentration. Using molecular beams with a small fraction of CH3I (1% in the expanded mixture) where smaller clusters should prevail, the production of I2 was found to be negligible. An upper estimate for the quantum yield of I2 from (CH3I)2 dimers was found to be less than 0.4%. Experiments with a higher fraction of CH3I (4% in the expanded mixture), which favor the formation of larger clusters, revealed an observable formation of I2, with an estimated translational temperature of about 820 K. We suggest that this observed I2 signal arises from the photodissociation of several CH3I molecules in the larger cluster by the same UV pulse, followed by recombination of two nascent iodine atoms is responsible for neutral I2 production.     

Copper(I) thiophenolate in copper N-heterocyclic carbene preparation

Copper(I) thiophenolate was considered as a copper source for the synthesis of Cu(I)-N-heterocyclic carbenes (Cu(I)-NHCs). It displayed a dual mode of reactivity allowing the synthesis of both thiophenolato-Cu(I)-NHCs via the free carbene in a one-pot procedure starting from imidazolium chlorides and chloro-Cu(I)-NHCs by a salt metathesis reaction starting from chloro-Ag(I)-NHCs.     

Formation of N-I charge-transfer bonds and ion pairs in polyiodides with imidotellurium cations

[((t)BuNH)Te(mu-N(t)Bu)(2)Te(N(t))Bu)][OSO(2)CF(3)] (4a) is obtained in quantitative yields by the treatment of [((t)BuN)Te(mu-N(t)Bu)(2)Te(N(t)Bu)] (1) with HCF(3)SO(3). The reaction of 4a with LiI and iodine in the molar ratio 1:1:4.5 affords a product that, upon recrystallization from acetonitrile, was found to be a solid solution of [((t)BuNH)Te(mu-N(t)Bu)(2)Te(N(t)Bu)](2)I(20) (5a) and [((t)BuNH)Te(mu-N(t)Bu)(2)Te(NH(t)Bu)](2)I(18) (5b). Consequently, the crystal structure is disordered, containing 88.3(1)% of 5a.2MeCN and 11.7(1)% of 5b.2MeCN. The I(20) framework is involved in two symmetry-equivalent N-I-I-I-I fragments, two I(3)(-) ions, and three I(2) molecules that are linked together by I...I secondary bonding interactions. The bonding in the N-I-I-I-I fragment can be considered in terms of the lp(N) --> sigma*(I(2)) and pi(I(2)) --> sigma*(I(2)) charge-transfer interactions involving one [((t)BuNH)Te(mu-N(t)Bu)(2)Te(N(t)Bu)](+) cation and two I(2) units. The N-I bond length of 2.131(7) A, the I-I distances of 3.118(1), 3.095(2), and 2.788(2) A, and the angle I(2)-I(2) angle of 84.75(4) degrees are consistent with this bonding scheme. The I-I bond distances in the two symmetry-equivalent I(3)(-) ions are 3.113(1) and 2.792(2) A, and those in two crystallographically independent I(2) molecules are 2.736(2) and 2.743(1) A. The formal I(18)(4)(-) anion in 5b.2MeCN consists of four I(3)(-) anions and three I(2) molecules linked by I...I secondary bonds. One crystallographically independent I(3)(-) anion is connected to the [((t)BuNH)Te(mu-N(t)Bu)(2)Te(HN(t)Bu)](2+) cation by two hydrogen bonds [H...I = 2.823(5) and 2.983(5) A; N...I = 3.697(8) and 3.857(9) A]. The I(3)(-) anions and I(2) molecules in 5b show virtually identical bond parameters to those in 5a. The treatment of 1 with iodine and the reactions of its methylated derivatives, [((t)BuNMe)Te(mu-N(t)Bu)(2)Te(N(t)()Bu)][OSO(2)CF(3)] and [((t)BuNMe)Te(mu-N(t)Bu)(2)Te(MeN(t)Bu)][OSO(2)CF(3)](2), with LiI and iodine also afford highly moisture-sensitive polyiodides, either by the formation of N-I charge-transfer complexes or by ionic interactions. The crystal structures of the partially hydrolyzed products, [((t)BuIN)Te(mu-N(t))Bu)(2)Te(mu-O)](2)(I(3))(2) (3), [((t)BuMeN)Te(mu-N(t)Bu)(2)Te(mu-O)](2)(I(3))(2) (6), and 6.2MeCN, are also reported.     

Darstellung und Fluoreszenzeigenschaften von Kupfer(I)-Carboxylaten

Preparation and Fluorescence Properties of Copper (I) Carboxylates By reduction of copper(II) carboxylates with ascorbic acid in aqueous solutions some aromatic copper(I) compounds can easily be obtained by precipitation. Powder x-ray photographs of copper(I) propionate and copper(I) monochloroacetate have similar characteristic interferences as copper(I) acetate, from which a layer structure is known. All the here described copper(I) carboxylates are fluorescent, indicating that oxygen atoms behave as sufficently strong donors, but most of them and especially those with tetragonal structure, do not change their fluorescence colour by cooling in liquid nitrogen like many copper(I) complexes with nitrogen bases do (fluorescence thermochromism). Fluorescence thermochromism occurs however at copper(I) 3-hydroxybenzoate. This presumably results from a lower symmetry.     

New insights into the mechanism of activation of atom transfer radical polymerization by Cu(I) complexes

The kinetics of activation of RX by a Cu(I) complex has been investigated in MeCN both in the absence and presence of halide ions. The system Cu(I)/L/X(-) (L = Me(6)TREN) is mainly composed of Cu(I)L(+), XCu(I)L and Cu(I)X(2)(-), but only Cu(I)L(+) is found to be an active catalyst reacting with RX.