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We present the activation of hydrogen peroxide by micellar imidazolium nitrates via H-bond formation in water, as shown by vibrational spectroscopy and supported by DFT calculations. Mechanistic insight into the interactions of the surfactant cation, the nitrate anion and H2O2 is given. The micelles solubilise and epoxidise cyclooctene in the aqueous phase.

The modular building principle of metal–organic frameworks (MOFs) presents an excellent platform to explore and establish structure–property relations that tie microscopic to macroscopic properties. Negative thermal expansion (NTE) is a common phenomenon in MOFs and is often ascribed to collective motions that can move through the structure at sufficiently low energies. Here, we show that the introduction of additional linkages in a parent framework, retrofitting, is an effective approach to access lattice dynamics experimentally, in turn providing researchers with a tool to alter the NTE behavior in MOFs. By introducing TCNQ (7,7,8,8-tetracyanoquinodimethane) into the prototypical MOF Cu3BTC2 (BTC = 1,3,5-benzenetricarboxylate; HKUST-1), NTE can be tuned between αV = −15.3 × 10–6 K–1 (Cu3BTC2) and αV = −8.4 × 10–6 K–1 (1.0TCNQ@Cu3BTC2). We ascribe this phenomenon to a general stiffening of the framework as a function of TCNQ loading due to additional network connectivity, which is confirmed by computatio...

New complexes of Pd(II) with cationic phthalimido-functionalized N-heterocyclic carbene (NHC), the cis-Diacetonitrile(chloro)[1-(2′-phthalamidoethyl)-3-methylimidazolin-ylidene]palladium(II) Hexafluorophosphate (and its CD3CN derivative) had been successfully used as catalyst in the Suzuki–Miyaura cross-coupling reaction. This complex have been studied by structural (XRD), spectroscopic (infrared, far-infrared and Raman) and theoretical (DFT and normal coordinate calculations) methods. Palladium is bound to two acetonitrile ligands and one-one chloride ion and phthalimido-functionalized imidazolium salt, [3-methyl-1-(2′-phthalimidoethyl) imidazolium] (L = ligand) in a square–planar cis arrangement. The molecular structure of the [PdCl(NCCH3)2L]+ was obtained by XRD and DFT geometry optimization. The two acetonitrile ligands exhibited two different Pd-N bonds a shorter one 2.080 A (opposite to Cl ion) and a longer one 2.120 A (trans to heterocyclic ligand). The cationic [PdCl(NCCH3)2L+] complex has as much as 132 fundamental modes and practically all of them have been assigned. The complex has no symmetry elements, but interpretation has been performed on the basis of local symmetries of its fragments. Tans-conformation of the bridging –CH2-CH2– group has been established from vibrational spectra, and this local structure avoided interaction of phthalimido moiety with the palladium center. Special attention has been paid for understanding and interpretation of the characteristic imidazolium ring vibrations connected to the strong electron donor phthalimido ring at 1553, 1397, 1347, 1218, 1149, 1118, 845, 748, 666, 629, 471, 245, 212, 124 and 104 cm−1 which bands are up shifted comparing to those of 2,3-dialkyl substituted ring modes. Clear differences were established between the fundamentals and force constants of the two differently coordinated acetonitrile. The more strongly coordinated CH3CN(1) has Raman bands at 2336, 958 and 279 cm−1 while the other CH3CN(2) has at 2321, 936 and 266 cm−1 like antisymmetric CN, CC and Pd-N stretching modes, respectively. The Pd-N stretching modes were assigned with the help of spectral and calculated data of CD3CN complex. For acetonitrile (1) the light and heavy stretching modes were 279 and 275 cm−1, respectively exhibiting 4 cm−1 isotope shift whyle those for acetonitrile (2) were as 266 and 264 cm−1 with less isotope shift. Rather small but different 1.630 and 1.493 Ncm−1 Pd-N stretching force constants were fitted for stronger and weaker bonded acetonitrile as compared to those of 3.931 Ncm−1 for [Pd(NCCH3)2]2+, and 4.050 Ncm−1 for cis-PtCl2(NCCH3)2. In contrast, the strongly weakened Pd-N bonds the Pd-Cl bond is enhanced and exhibiting relative high 2.03 Ncm−1 force constants in comparison with 1.53 Ncm−1 of [PdCl4]2- anion. The enhanced Pd-Cl bond strength is escorted by strong weakening of Pd-acetonitrile coordination. Surprisingly, from DFT calculation and spectroscopic data higher Pd-N force constant was obtained for the Pd-N bond with longer bond length and opposite, lower force constant for shorter Pd-N bond. These unusual discrepancies between bond lengths and bond force constants can be explained with the presence of electron-rich σ-donating ligand opposite to acetonitrile (1) which lead to enhancement of Pd-N bond. These specific properties of coordination sphere of [PdCl(NCCH3)2L]+ complex providing possibilities for easily releasing acetonitrile ligands during catalytic processes and give reasonable structural explanation of its high catalytic activity.

Vibrational spectroscopic study of crystalline copper hexacyanoferrate complexes of composition K4CuII6 [FeII(CN)6]4·nH2O (1) and CuII6[FeIII(CN)6]4·nH2O (2) with -Cu-N≡C-Fe- bridging structures ha...

Tetrachloroethylene (C2Cl4) has been used widely as a solvent and dry cleaning agent, but was later specified as possible human carcinogen. As a result, its safe treatment became a priority. In this paper, we report on its decomposition in an atmospheric radiofrequency thermal plasma reactor. Main components of the exhaust gases were determined by Fourier transform infrared spectroscopy. We found that complete decomposition can be achieved in either oxidative or reductive conditions but not in neutral one. The solid soot product was characterised by transmission electron microscopy and specific surface area measurement. Organic compounds adsorbed on the surface of the soot were extracted by toluene and comprised, based on gas chromatography mass spectrometry, of various perchlorinated aliphatic (for example hexachlorocyclopentadiene) and aromatic compounds (like hexachlorobenzene, octachloronaphthalene or octachloroacenaphthylene). Several nitrogen containing molecules were also identified whose presence are rare during thermal plasma treatments. Further investigation of the extract by mass spectrometry revealed various higher molar mass chlorinated carbon clusters and two types of fullerenes (C60 and C70).

The strength and geometry of adsorption of substituted phenylpyruvates on silver surface was studied by means of surface enhanced Raman spectroscopy (SERS) using silver sol. 2′-nitrophenylpyruvates were used as starting materials in a newly developed heterogeneous catalytic asymmetric cascade reaction to produce substituted quinoline derivatives. Substituents on the aromatic ring of the starting materials had significant influence on the yield of the desired quinoline derivatives. Product selectivity of the transformation of nitrophenylpyruvates were enhanced by the acid added. The geometry and the strength of the adsorption are assumed to play an important role in the outcome of this reaction, so we have tried to find correlation between the structure of adsorbed phenylpyruvates and their catalytic performance. Based on the results of our spectroscopic measurements, the enol form is predominant in the series of phenylpyruvates in solid form and methanol solutions. Stronger adsorption of phenylpyruvates in acidic media through oxygen atoms was indicated by the increased enhancement in the SERS spectrum. The nitro group of 2′-nitrophenylpyruvates has no direct role in the adsorption on Ag surface. This observation has explained why the hydrogenation of the keto group (presumably via the enol form) occurs preferentially and why the formation of the undesired indole derivatives requiring reduction of the nitro group is suppressed. The SERS behavior has helped to get a closer look on the first step of adsorption of starting materials contributing to a better understanding of the cascade reaction studied, thus providing a better flexibility in catalyst design.

New composite materials based on clay minerals had been prepared by reductive calcination. These materials exhibit very strong infrared (IR) emission at quite low temperatures. The structural prope...

The modular building principle of metal-organic frameworks (MOFs) presents an excellent platform to explore and establish structure-property relations that tie microscopic to macroscopic properties. Negative thermal expansion (NTE) is a common phenomenon in MOFs and is often ascribed to collective motions that can move through the structure at sufficiently low energies. Here, we show that the introduction of additional linkages in a parent framework, retrofitting, is an effective approach to access lattice dynamics experimentally, in turn providing researchers with a tool to alter the NTE behavior in MOFs. By introducing TCNQ (7,7,8,8-tetracyanoquinodimethane) into the prototypical MOF Cu

Decomposition of poly(vinyl chloride) (PVC) was studied in inductively coupled radiofrequency thermal plasma in neutral, oxidative and reductive conditions. The exhaust gases were analysed by Fourier transform infrared spectroscopy (FT-IR), and their main components were identified as CO, CO 2 , C 2 H 2 , H 2 O and HCl. The weaker bands in the infrared spectra were assigned by density function theory calculations and P–R separation method. The extent of PVC decomposition was calculated from the amount of solid soot, which was also studied by transmission electron microscopy (TEM) for morphology and composition. Organic compounds adsorbed on the surface of the soot were extracted by toluene and analysed by gas chromatography mass spectrometry (GC/MS). The extracts comprised of various polycyclic aromatic hydrocarbons (PAHs) and their methylated and chlorinated derivatives. Their amount was greatly affected by the experimental conditions. The presence of oxygen decreased the formation of PAHs, while it increased the formation of polychlorinated PAH compounds. In the presence of hydrogen PAH formation was observed. However, dioxin or furan derivatives were not detected in the decomposition products.

The hydrogen storage materials ASiH(3) (A=K and Rb) represent complex metal hydrides built from metal cations and pyramidal SiH3- ions. At room temperature, SiH3- moieties are randomly oriented because of dynamical disorder (-modifications). At temperatures below 200K, ASiH(3) exist as ordered low-temperature () modifications. The vibrational properties of -ASiH(3) were characterized by a combination of Raman spectroscopy and inelastic neutron scattering. Internal modes of SiH3- are observed in the spectral range 1800-1900cm(-1) (stretching modes) and 890-1000cm(-1) (bending modes). External modes are observed below 500cm(-1). Specifically, SiH3- librations are between 300-450cm(-1) and 270-400cm(-1) for A=K and Rb, respectively, SiH3- translations are between 95 and 160cm(-1), K+ translations are in the range 60-100cm(-1) and Rb+ translations in the range 50-70cm(-1). The red-shift of libration modes for A=Rb is associated with a 15-30% reduction of the libration force constants of SiH3- ions in -RbSiH3. This correlates with a lower temperature for the - order-disorder phase transition (278 vs 298K). Libration modes become significantly anharmonic with increasing temperature but are maintained up to at least 200K. The vibrational properties of ASiH(3) compare well to those of alkali metal borohydrides ABH(4) (A=Na-Cs).

The strength and geometry of adsorption of substituted propenoic acids on silver surface were studied by means of surface enhanced Raman spectroscopy (SERS) using silver sol. Based on their SERS behavior, two classes of phenylpropenoic acids studied were distinguished. The first class of propenoic acids (atropic acid, (E)-2,3-diphenylpropenoic acid, (E)-2-(2-methoxyphenyl)-3-phenylpropenoic acid, (E)-2,3-di-(4-methoxyphenyl)phenylpropenoic acid and (E)-2-(2-methoxyphenyl)-3-(4-fluorophenyl)propenoic acid) has shown strong charge transfer (CT) effect. We suggest bidentate carboxyl bonded species based on the SERS enhanced bands of νCOO− around 1394 cm−1 and νC―C of the ―C―COO− moiety at 951 cm−1. In these series the plane of the α-phenyl group (γCH out-of-plane vibrations at 850–700 cm−1) is almost parallel to the silver surface, while the β-phenyl group is in tilted position depending on the type and the position of substituent(s) showing strong SERS enhanced bands of νCC + βCH (in-plane mode) at 1075 cm−1, νCC (ring breathing mode, in-plane) at 1000 cm−1 and γCCC (out-of-plane mode) around 401 cm−1. The other class of propenoic acids (cinnamic acid, (E)-2-phenyl-3-(4-methoxyphenyl)propenoic acid) has shown weak electromagnetic (EM) enhancement (CC bands is enhanced in cinnamic acid). In this case no significant carboxyl enhancement was observed, so we suggest that adsorbed species lie parallel to the surface. The two types of adsorption can be related to the dissociation ability of the carboxylic group. In the first case the carboxylic H dissociates, while in the second case it does not, as indicated also by the characteristic νCO band at 1686 cm−1 in the FT-Raman spectra of methanolic solutions. Copyright © 2015 John Wiley & Sons, Ltd.

A series of salts containing the weakly coordinating cations (WCC) 1-butyl-3-methylimidazolium ([Bmim]+), 1-butyl-2,3-dimethylimidazolium ([Bdmim]+), 1-dodecyl-3-methylimidazolium ([C12mim]+), tetrabutylphosphonium ([PBu4]+), tributyltetradecylphosphonium ([P4;4;4;14]+), tetrabutylammonium ([NBu4]+), and 1,1,3,3-tetramethylguanidium ([TMG]+) and fluorinated tetraarylborate anions of the type [B(ArF)4] (ArF =C6F5, C6H3-3,5-(CF3)2) were synthesized and characterized. The influence of cations and anions on the physical properties of the obtained compounds was examined. In case of the compound [TMG][B(C6F5)4] hydrogen-fluorine contacts between cation and anion are present in the solid state. Owing to H···F contacts between hydrogen peroxide and the fluorine substituents of the anion and the resulting activation of H2O2 in solution, the compound [P4;4;4;14][B(C6H3-3,5-(CF3)2)4] is applicable as an efficient mediator for the oxidation of sulfides to sulfoxides

LiP15 was synthesized by reaction of the elements in the presence of CuCl2 as a mineralizer additive in sealed silica ampoules at 823 K. The product was characterized by powder and single-crystal X-ray diffraction experiments, quantum chemical calculations and IR and Raman spectroscopy. It crystallizes in the triclinic crystal system in space group P with the lattice parameters a = 6.974(1) A, b = 9.008(1) A, c = 11.294(2) A, α = 104.51(1)°, β = 93.78(1)°, γ = 106.330(10)° and V = 652.1 A3. The structure of the phosphorus-rich polyphosphide consists of tubular polyphosphide strands that are coordinated by lithium atoms to form double strands with an antiparallel arrangement. Quantum chemical investigations and structure optimizations were applied to localize the Li positions within the polyphosphide framework, and a full factor group analysis was done to understand the complex IR and Raman spectra of the title compound. LiP15 does not crystallize isotypically to compounds with the higher homologues of lithium but forms its own structure type, in contrast to previous reports. On the basis of our results, a LiP15 polymorph isotypic to KP15 might exist energetically separated by a few kJ/mol. We also predict that a second KP15 polymorph with the reported LiP15 structure would be energetically as favourable as the known one.

A cationic phthalimido-functionalized N-heterocyclic carbene (NHC) palladium(II) complex has been synthesized from [3-methyl-1-(2′-phthalimidoethyl)imidazolium] hexafluorophosphate ([NHCMe,PhtH]PF6) by transmetalation and isolated in 67 % yield. The title complex has been applied as catalyst in the Suzuki–Miyaura cross-coupling reaction under benign aqueous conditions. The catalyst is active without any observable initiation period. High average turnover frequencies (TOFs) of up to 55000 h–1 have been reached with catalyst concentrations as low as 0.01 mol-%.

To date, only few examples of tetrazolylidene carbenes coordinated to transition metal complexes have been described. A direct comparison of "normal" tetrazolylidenes (1,4-substitution pattern) and "abnormal" tetrazolylidenes (also referred to as "mesoionic carbenes"; 1,3-substitution pattern) has not been performed at all. In this work, we describe coordination of both ligand types to a row of transition metals. For example, the first examples of tetrazolylidene Mo, Ag, or Ir complexes have been isolated and fully characterized. The mesoionic tetrazolylidene Ag compound 2d is shown to be a viable carbene transfer reagent. By means of NMR, IR, and Raman spectroscopy, as well as X-ray crystallography and computational results, the pronounced differences between the two ligand substitution patterns are highlighted. It is shown that simply changing the position of a methyl group from N3 to N4 in the heterocycle can cause enormous differences in ligand characteristics.

Novel organic–inorganic hybrid nanotubes containing silica and ethane (EtSNT), ethylene (ESNT) and acetylene (ASNT) units, as well as brominated ESNT (Br-ESNT) and glycine-modified Br-ESNT (Gly-ESNT) have been studied by IR and Raman spectroscopy. The results are compared with the spectral features for conventional silica nanotubes (SNT) and amorphous silica. Bands peculiar to organic moieties have been detected and assigned. Assignment of the silicate backbone vibrations was based on the results of normal coordinate calculations. Furthermore, characteristic silicate, so-called ‘nanotube’ vibrations have been identified and their band positions have been summarized to serve as a future reference for such compounds. SiOSi antisymmetric stretchings were observed in the range 1000–1110 cm−1, while the symmetric stretchings appeared between 760 and 960 cm−1 for EtSNT, ESNT and Br-ESNT. Force constants have been refined for models of the repeating structure units: O3SiOSi(OSi)3 for SNT and SiCHnCHnSi(OSi)3 for organosilica nanotubes (n = 2, EtSNT; n = 1, ESNT and n = 0, ASNT). The calculated SiO stretching force constants were increased from 4.79 to 4.88 and 5.11 N cm−1 for EtSNT, ESNT and ASNT, respectively. The force constants have been compared with those for several silicates and SiO bond length are predicted and discussed.

The catalytic activity of (2,6-dimethylphenyl)trioxorhenium (XTO) for the epoxidation of cyclooctene is presented. Solutions of hydrogen peroxide and tert-butyl hydrogen peroxide (TBHP) in THF or CH2Cl2 were applied as oxidizing agent–solvent mixtures. Cyclooctene oxide yields are higher with TBHP than with H2O2. Application of non-coordinating solvents as reaction media increases both yields and reaction rates. The possible active species is analyzed by 17O NMR and Raman spectroscopy.

The L-cysteine zwitterions in the orthorhombic crystal structure and in aqueous solution, including the deuterated isotopologues HSCD2CH(NH3 +)COO−, DSCH2CH(ND3 +)COO−, and DSCD2CH(ND3 +)COO−, have been studied by mid-infrared, far-infrared, and Raman spectroscopy. Density functional theory (DFT) calculations were performed for an equilibrium molecular geometry of the cysteine zwitterion to obtain vibrational frequencies of fundamental modes, infrared (IR) and Raman intensities, and the depolarization ratio of the Raman bands and combined with normal coordinate force field analyses. The force field obtained for dissolved (in H2O and D2O) cysteine, based on the 4 × 36 experimental fundamental modes of the four isotopologues, was successfully transferred to the two conformers in the solid state. The experimentally observed multiple bands (generally doublets) of L-cysteine and its deuterated isotopologues in the solid state were interpreted based on the coexistence of two conformers in the unit cell...

The synthesis and characterization of novel organic–inorganic hybrid nanotubes containing silica and ethane (EtSNT), ethylene (ESNT) and acetylene (ASNT) units are presented. The unsaturated hydrocarbon linkers can be applied for a chemical functionalization of the surface of the silica nanotubes, e.g. for the grafting of organic/inorganic or organometallic molecules. These new materials are synthesized via a template method using V3O7·H2O fibers and characterized by solid state MAS-NMR, FT-IR, TEM and elementary analysis. In a first approach to potential applications of these materials, the grafting of glycine on ESNT by treatment of the C C groups with Br2 and subsequent substitution by glycine is investigated. The resulting material is characterized by solid state MAS-NMR, FT-IR, XRD, TGA, BET adsorption measurements and elementary analysis.

Mid-infrared, far-infrared and Raman vibrational spectroscopic studies were combined with DFT calculations and normal coordinate force field analyses for N,N’-dimethylurea (DMU), N,N,N’,N’-tetramet ...

FT-Raman spectra of human enamel surfaces from sound, affected (with 1 cavity) and highly affected (with at least 3 cavities) tooth samples were analyzed by principal component analysis (PCA). Major differences between the unaffected and affected tooth samples seem to arise from the structural changes along the c-axis of hydroxyapatite, the chief crystalline component of human dental enamel. Based on Fisher index calculations, the most discriminative value was obtained for the intensity of the only Raman active nu 2PO43- (E-1) symmetric deformation mode at 428 cm(-1). Moreover, these changes can be observed through the whole tooth enamel surface, establishing a predisposition to caries correlated to chemical and structural composition of tooth enamel. No spectral changes regarding the CO32- substitution were detected by both nondestructive FT-Raman and FTIR (Fourier transform infrared) spectroscopy of the powdered teeth samples. Copyright (C) 2009 John Wiley & Sons, Ltd.

IR, Raman measurements, and ab initio molecular dynamics simulations have been carried out to describe and understand the structural and dynamic behavior of hydrated Pt2+ ion in water. The experiments have revealed strong red-shifted O–H bond frequencies and blue-shifted ligand deformation bands. The simulations have showed that the presence of the doubly charged cation and the enhanced hydrogen bond formations between the first and second shells result in significant structural changes in the first solvation shell, which in turn yield the characteristic shifts in the vibrational spectra. The weakening of the ligand O–H bonds and the strengthened hydrogen-bonds around the cation can be accounted for as the result of the strong Coulombic field of the Pt(II)-ion. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

Investigation on time-dependent layer formation was performed on high purity polycrystalline zinc surface in reaction with aqueous solution of 1, 5-diphosphono-pentane (DPP) at room temperature. Film evolution was characterized by X-ray photoelectron spectroscopy, contact angle, atomic force microscopy, glow discharge optical emission spectroscopy and detailed infrared reflection absorption spectroscopy measurements. Development of a partly crystalline zinc-diphosphono-pentane conversion layer of increasing thickness with time was determined by consistent evaluation of the results. The formed layers turned the hydrophobic zinc surface to hydrophilic. The conversion-type interaction of diphosphonic acid compounds with the oxidized zinc surface resulting in zinc-diphosphonate salt was unambiguously justified by XPS and GD-OES analysis. The corrosion behaviour of the coated zinc substrate was studied using electrochemical impedance spectroscopy (EIS). The formed layers show significant protective effect in sodium-sulphate solutions. It was shown, that under the applied conditions, a 4 h treatment is necessary to obtain 75% protection efficiency after 4 h of immersion into the Na 2 SO 4 .

Mid infrared, far-infrared and Raman spectroscopic studies, combined with force field analyses, were performed for the 1 hydrated platinum(II) and palladium(II) ions and cis-diammineplatinum(II) complex in acidic aqueous solutions. Simplified Density Functional Theory (DFT) calculations were made for the equatorial plane of the platinum complexes. Careful subtraction of solvent spectra allowed a number of 'internal' modes of coordinated H(2)O and NH(3) to be determined as weak residual bands. The [Pt(OH(2))(6)](2+) and [cis-Pt(NH(3))(2)(OH(2))(4)](2+) complexes were found to be six-coordinated with four ligands strongly bound in an equatorial plane. The assignments of the vibrational modes in the equatorial plane could be performed on the basis of the experimental observations and by comparison with metal-ligand vibrations of square-planar complexes, aided by normal coordinate calculations. For the weakly coordinated axial aqua ligands, the low wavenumber range and the polarizibility properties allowed the assignments of the bands at about 365 and 325 cm(-1) to the stretching modes of one short and one longer Pt - O* bound to axial aqua ligands, respectively. A similar picture with even less strongly bound axial water molecules emerges from Raman spectroscopy data for the hydrated palladium(II) ion, [Pd(OH(2))(6)](2+). The results are consistent with a description of the [Pt(OH(2))(6)](2+) and [Pd(OH(2))(6)](2+) aqua ions in C(4v) symmetry, and with the [cis-Pt(NH(3))(2)(OH(2))(4)](2+) complex in the Cs point group, and also in qualitative agreement with the structures devised from previous extended X-ray absorption fine structure (EXAFS) measurements.

Some seashells of the Philippine venus species and sea coral of Pontes sp. were studied by means of FT-Raman, Fourier transform infrared spectroscopy (FTIR) and Far-FTIR spectroscopic methods. The Raman spectra show that both Porites sp. and P. venus are of aragonite-structured CaCO3. Detailed spectral analysis, however, reveals some small differences, due to differences in the crystallite size or habit and to different minor element contents. IR spectra show that Porites sp. contains also some small quantities of calcite-structured carbonates. The I…2 band (shoulder) of calcite at 875.7 cm-1 is present in the IR spectrum. The separation of the two I…2 bands (856.4 cm-1 for aragonite and 875.7 cm-1 for calcite) suggests the absence of solid solution of the two polymorphic phases of CaCO3. Spectroscopic results were confirmed also by X-ray powder diffraction measurements.

The objective of our studies was to investigate the layer formation of 1, 5-diphosphonopentane (DPP) on zinc surface from aqueous solution. For surface treatment, water based solutions of 1, 5-diphosphono-pentane was applied with different treatment times. Evidence of the adsorption of the diphosphonic acid on the zinc surface was obtained using the Infrared Reflection Absorption Spectroscopy (IRRAS).

Interactions of a series of indole-3-alkanoic acids (with n-alkanoic acid side-chains from C1 to C4) with iron(III) in acidic aqueous solutions have been shown to comprise two parallel processes including complexation and redox transformations giving iron(II) hexaaquo complexes. The structure and composition of the reaction products are discussed, as analysed using a combination of instrumental techniques including 57Fe Mössbauer, vibrational and HNMR spectroscopies.

The new crystalline compounds Tl2Ni(CN)(4) and Tl2Pd(CN)(4) were synthesized by several procedures. The structures of the compounds were determined by single-crystal X-ray diffraction. The compounds are isostructural with the previously reported platinum analogue, Tl2Pt(CN)(4). A new synthetic route to the latter compound is also suggested. In contrast to the usual infinite columnar stacking of [M(CN)(4)](2-) ions with short intrachain M-M separations, characteristic of salts of tetracyanometalates of Ni-II, Pd-II, and Pt-II, the structure of the thallium compounds is noncolumnar with the two Tl-I ions occupying axial vertices of a distorted pseudo-octahedron of the transition metal, [MTl2C4]. The Tl-M distances in the compounds are 3.0560(6), 3.1733(7), and 3.140(1) A for Ni-II, Pd-II, and Pt-II, respectively. The short Tl-Ni distance in Tl2Ni(CN)(4) is the first example of metal-metal bonding between these two metals. The strength of the metal-metal bonds in this series of compounds was assessed by means of vibrational spectroscopy. Rigorous calculations, performed on the molecules in D-4h point group symmetry, provide force constants for the Tl-M stretching vibration constants of 146.2, 139.6, and 156.2 N/m for the Ni-II, Pd-II, and Pt-II compounds, respectively, showing the strongest metal-metal bonding in the case of the Tl-Pt compound. Amsterdam density-functional calculations for isolated Tl2M(CN)(4) molecules give Tl-M geometry-optimized distances of 2.67, 2.80, and 2.84 A for M = Ni-II, Pd-II, and Pt-II, respectively. These distances are all substantially shorter than the experimental values, most likely because of intermolecular Tl-N interactions in the solid compounds. Time-dependent density-functional theory calculations reveal a low-energy, allowed transition in all three compounds that involves excitation from an a(1g) orbital of mixed Tl 6p(z)-M nd(z)(2) character to an a(2u) orbital of dominant Tl 6p(z) character.

Seven important air pollutants have been investigated by photolysis-assisted FT-IR spectroscopy. This technique renders invisible the spectra of water and carbon dioxide, which are two of the main concerns in long-path infrared spectroscopy. A cell, equipped with a UV lamp, was used to oxidise the analyte in the air sample and the spectrum recorded was used as a new background for the original sample spectrum. The optimum UV irradiation time and correctness of the concentrations were determined for this technique and compared with those from traditional methods. The signal-to-noise (S/N) ratios of the so-called "shadow spectra" were better than, or at least comparable to, the S/N ratios in the absorbance spectra obtained by using as background an air or an evacuated cell reference and subtraction of the spectra of water and carbon dioxide from a spectral library. The detection limits for the volatile organic compounds investigated have been improved by using this new method in which an appropriate background spectrum can be obtained quickly. The limitations of the method are that it cannot be applied to non-UV reactive compounds, such as methane, and the detection limits can be appreciably degraded when bands due to ozone in the shadow spectra overlap with those of the compounds under investigation.

The Zn 4 O(RCO 2 ) 6 complexes of a selection of straight- and branched-chain carboxylic acids have been prepared in CCl 4 and characterized by their 13 C NMR, 1 H NMR and mid-FT-IR spectra. Their structural stability was studied by FT-IR-spectroscopy over a 4-day long period of time in CCl 4 solution and as cast films. The observed characteristic spectroscopic features have been discussed. The cast film samples showed extremely diverse behaviour from instant decomposition to the perfect conservation of the original T d symmetry, even though water was not excluded from the system. An explanation, supported by ab initio quantum chemical calculations on the conformation of the free carboxylate ions with various alkyl-chains, has been given for the diverse behaviour of the samples. Formation of a hydrocarbon moiety, with somewhat extended anti-periplanar (all- trans ) conformation, perpendicular to the carboxylate plane was the essential factor in the preservation of the structure and the quaternary α-carbon was an additional requirement to sustain its symmetry. Two attempts at preparing the corresponding Zn 4 O(RCO 2 ) 6 complexes from water have been successful in the cases when the R-groups fulfilled the requirements in geometry stated above.

Copper(I) and silver(I) complexes of formulae [Cu(NCCH3)4]+[A]− ([A]− = [B(C6F5)4]− (1), {B[C6H3(CF3)2]4}− (2), [(C6F5)3B–C3H3N2–B(C6F5)3]− (3), and [Ag(NCCH3)4]+[B(C6F5)4]− (4) are examined with particular emphasis on the strength of their M–N bond and its influence on the catalytic performance of these complexes in cyclopropanation and aziridination. To examine the strength of the M–N interactions, vibrational spectra of the related hydrogenated and deuterated species [Cu(NCCH3)4]+, [Cu(NCCD3)4]+, [Ag(NCCH3)4]+, and [Ag(NCCD3)4]+ are also determined. It is found that the metal–nitrile bond strength is an important factor for the catalytic activity of the respective complexes.

Infrared, far-infrared and Raman spectra of Re2(O2CCH3)4X2 (X = Cl, Br) and Re2(O2CCD3)4Cl2 have been recorded. Assignments of the vibrational spectra of Os2(O2CCH3)4Cl2 and its deuterated derivative have been completed together with the Re complexes on the basis of normal-coordinate analysis. Force constant calculation was made for the acetate ion as well as for a four-atomic unit (with the CH3 and CD3 groups considered as point masses) using optimized masses of 16.7, 17.8, 20.5 and 21.6 for 12CH3, 13CH3, 12CD3 and 13CD3 groups, respectively. The force constants of the acetate ion have been adopted to the starting force field of the M2(O2CCH3)4X2 type complexes. The metal–halide (0.889, 0.997 and 1.286 N cm−1) and metal–metal stretching (3.32, 3.34 and 3.57 N cm−1) force constants were obtained for Re2(O2CCH3)4Cl2Re2(O2CCH3)4Br2 and Os2(O2CCH3)4Cl2 complexes, respectively. It was shown that the so-called diatomic approximation in most cases overestimates the M–M stretching force constants by 30–40%. Much better correlation has been obtained to fit these force constants, which produced values very close to those obtained by full normal-coordinate calculations. The Re–Re stretching force constants showed a reasonable correlation with the Re–Re bond distances for 18 rhenium complexes.

Several Schiff-base ligands readily form complexes with methyltrioxorheniumA (MTO) by undergoing a hydrogen transfer from a ligand-bound OH group to a ligand N atom.The resulting complexes are stable at room temperature and can be handled and stored in air without prob- lems.Due to the steric demands of the ligands they display distorted trigonal- bipyramidal structures in the solid state, as shown by X-ray crystallogra- phy, with the O moiety binding to the Lewis acidic Re atom and the Re- bound methyl group being located either in cis or trans position to the Schiff base.In solution, however, the steric differences seem not to be main- tained, as can be deduced from 17 O NMR spectroscopy.Furthermore, the Schiff-base ligands exchange with donor ligands.Nevertheless, the cata- lytic behaviour is influenced signifi- cantly by the Schiff bases coordinated to the MTO moiety, which lead either to high selectivities and good activities or to catalyst decomposition.A large excess of ligand, in contrast to the ob- servations with aromatic N-donor li- gands, is detrimental to the catalytic performance as it leads to catalyst de- composition.

Fourier transform infrared (FT-IR) spectroscopy has been adapted to control the quality of light bulbs made from silica glass. Such light bulbs contain a molybdenum accessory which, if contaminated with carbon, during the melting procedure of bulb fabrication, can cause the production of carbon monoxide. This CO can be trapped in small gas cavities in the silica glass body of the bulb. A method has been developed for the detection of CO and the total pressure within these gas cavities by traditional FT-IR spectrometry using a spectral resolution of 0.5 cm(-1). The concentration of CO was determined by using a classical least-squares (CLS) method, and the accuracy of concentration determination is reported for the case with sample and reference spectra recorded at different pressures. The total pressure in the cavities was established by two different methods: either by CLS fitting of reference spectra to sample spectra or fitting a Voigt line shape function to the spectral lines within the CO fundamental stretching band. In the latter method, the width of the lines was determined and pressure-broadening coefficients are given and compared with high-resolution data from the literature. According to the measurements, 0.55-0.80 atm total pressure and 0.8-4.0% (v/v) CO was determined in the gas cavities. This method can also be applied to determine the total pressure in similar enclosed spaces in which an appropriate indicator gas component exists.

A comprehensive comparison of long‐path extractive and open‐path FTIR techniques on the bases of the available literature and on our own experience at the wastewater treatment plant of a chemical factory has been made. Two equalization basins were investigated and it was supposed that all the surface of the wastewater emits polluting compounds smoothly, since the atmospheric dispersion was found to be ideal at both sites, there were no significant chemical reactions, and the basin dimensions were rather small (7×16 m2 and 37×79 m2, respectively). Since the possibilities were different, rather different optimal spectral parameters (resolution, scan numbers, path length) were chosen for field and laboratory measurements. The S/N ratio of laboratory spectra was about 50–100 times higher than that of field spectra, which resulted in higher precision and lower detection limits of the measurements, and comparing to field measurements an additional compound (chloroform) was detected. On the other hand, ...

The chemical reactions between iron(III) and indole-3-acetic (IAA), -propionic (IPA), and -butyric (IBA) acids were studied in acidic aqueous solutions. The motivation of this work was that IAA is one of the most powerful natural plant-growth-regulating substances (phytohormones of the auxin series). Mossbauer spectra of the frozen aqueous solutions of iron(III) with indole-3-alkanoic acids as ligands (L), showed parallel reactions between Fe3+ and the ligands. Partly, it resulted in a complex formation which precipitated in aqueous solution and partly, in a redox process with iron(II) and the oxidised indole-3-alkanoic acids as products. The Mossbauer parameters of the Fe2+ species suggested a hexaaquo coordination environment. The chemical composition and coordination structure of the precipitated complexes were investigated using elemental analysis, Mossbauer spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopic techniques. The complexes were soluble in some organic solvents. So, Mossbauer, FTIR and solution X-ray diffraction measurements were carried out on the solution of complexes in acetone, hexadeutero acetone and methanol, respectively. The data obtained supported the existence of the μ-dihydroxo-bridging structure of the dimer: [L2Fe FeL2] (where L is indole-3-propionate, -acetate or -butyrate).

The basic principles and methods of FTIR spectroscopy of the atmosphere were summarized in our previous paper 1. Thanks to the continuous technical development of FTIR spectroscopy (increasing throughput, dynamic alignment, more sensitive detectors, brighter sources, increasing scanning speed, development of focal plane array detectors, flexible spectral manipulations and data handling, etc.) in the last decade, this method has offered a great number of unique applications. In this review article, attempt to summarize the results of the most significant and frequent applications of FTIR spectroscopy to the study of the atmosphere. The possibilities of techniques applied in this field, the extractive and open path measurement methods, and the in situ IR absorption measurements such as remote sensing using the sun, the sky, or natural hot objects as IR sources of radiation are discussed. We have made a special focus to FTIR emission spectroscopy, the so‐called passive technique, since there are a n...

Homogeneous catalytic processes mediated by silver(I) complexes are relatively rare. This work describes the synthesis and characterization of acetonitrile ligated silver salts with three weakly coordinating anions [B(C6F5)4]−, [B{C6H3(CF3)2}4]− and [(C6F5)3B–C3H4N2–B(C6F5)3]−. The silver cation is coordinated either by four or by two acetonitrile ligands. All examined Ag(I) complexes show catalytic activity in coupling reactions of terminal alkynes with aldehydes and amines.

In recent years Fourier transform infrared (FTIR) spectroscopy has been the dominant technique used for measuring the infrared (IR) absorption and emission spectra of most materials, with substantial advantages in signal‐to‐noise ratio, resolution, speed, and detection limits. The major advantage of the FTIR technique over other spectroscopic methods is that practically all compounds show characteristic absorption/emission in the IR spectral region and based on this property they can thus be analyzed both quantitatively and qualitatively. The quest for highly sensitive detection methods for atmospheric trace gas samples, either in laboratory setup or in outdoor remote sensing, has been on agenda for several decades. The fast and intensive development of FTIR spectroscopic techniques has propelled the progress of trace gas analysis of the atmosphere. Since the early 1970s the number and scope of FTIR atmospheric measurements has increased steadily. In this review article we are making an attempt t...

Vibrational spectra (IR, Raman, inelastic neutron scattering) were measured of natural wardite (ideal formula NaAl 3 (OH) 4 (PO 4 ) 2 ·2 H 2 O) from Trauira, Brazil, with the main impurities Fe and Ca. The spectra are discussed on the basis of a symmetry analysis restricted to one layer in the four-layer structure. The band pattern in the ν (OH) region is due to two different Al 2 OH groups and their correlation coupling; their deformations δ and γ are assigned based on IR and INS spectra. Contributions of the hydrogen-bonded H 2 O molecules are discussed, as are the vibrations of the AlO 6 octahedra dominating the Raman spectrum. From the fundamentals ν (OH) of the OH groups and their overtones anharmonicity constants have been estimated.

Mossbauer spectroscopic studies were carried out in acidic (pH 2.3) 57FeIII nitrate containing aqueous solutions of indole-3-butyric acid (IBA), rapidly frozen in liquid nitrogen at various periods of time after mixing the reagents. The data obtained show that in solution in the presence of IBA, iron(III) forms a complex with a dimeric structure characterised by a quadrupole doublet, whereas without IBA under similar conditions iron(III) exhibits a broad spectral feature due to a slow paramagnetic spin relaxation which, at liquid nitrogen temperature, results in a large anomalous line broadening (or, at T = 4.2 K, in a hyperfine magnetic splitting). The spectra of 57FeIII+IBA solutions, kept at ambient temperature under aerobic conditions for increasing periods of time before freezing, contained a gradually increasing contribution of a component with a higher quadrupole splitting. The Mossbauer parameters for that component are typical for iron(II) aquo complexes, thus showing that under these conditions gradual reduction of iron(III) occurs, so that the majority (85%) of dissolved iron(III) is reduced within 2 days. The Mossbauer parameters for the iron(III)-IBA complex in aqueous solution and in the solid state (separated from the solution by filtration) were found to be similar, which may indicate that the dissolved and solid complexes have the same composition and/or iron(III) coordination environment. For the solid complex, the data of elemental analysis suggest the following composition of the dimer: [L2Fe-(OH)2-FeL2] (where L is indole-3-butyrate). This structure is also in agreement with the data of infrared spectroscopic study of the complex reported earlier, with the side-chain carboxylic group in indole-3-butyrate as a bidentate ligand. The Mossbauer parameters for the solid 57FeIII-IBA complex at T = 80 K and its acetone solution rapidly frozen in liquid nitrogen were virtually identical, which indicates that the complex retains its structure upon dissolution in acetone.

Hexakis(dimethyl sulfoxide)scandium(III) iodide, [Sc(OS(CH(3))(2))(6)]I(3) contains centrosymmetric hexasolvated scandium(III) ions with an Sc-O bond distance of 2.069(3) angstroms. EXAFS spectra yield a mean Sc-O bond distance of 2.09(1) angstroms for solvated scandium(III) ions in dimethyl sulfoxide solution, consistent with six-coordination. Raman and infrared absorption spectra have been recorded, also of the deuterated compound, and analysed by means of normal coordinate methods, together with spectra of dimethyl sulfoxide. The effects on the vibrational spectra of the weak intermolecular C-H...O interactions and of the dipole-dipole interactions in liquid dimethyl sulfoxide have been evaluated, in particular for the S-O stretching mode. The strong Raman band at 1043.6 cm(-1) and the intense IR absorption at 1062.6 cm(-1) have been assigned as the S-O stretching frequencies of the dominating species in liquid dimethyl sulfoxide, evaluated as centrosymmetric dimers with antiparallel polar S-O groups. The shifts of vibrational frequencies and force constants for coordinated dimethyl sulfoxide ligands in hexasolvated trivalent metal ion complexes are discussed. Hexasolvated scandium(iii) ions are found in dimethyl sulfoxide solution and in [Sc(OSMe(2))(6)]I(3). The iodide ion-dipole attraction shifts the methyl group C-H stretching frequency for (S-)C-H...I(-) more than for the intermolecular (S-)C-H...O interactions in liquid dimethyl sulfoxide.

The complexes (η5-C5R5)MoO2Cl (R = H, CH3 (Me), CH2Ph (Bz)) are readily prepared from the parent carbonyls (η5-C5R5)Mo(CO)3Cl upon reaction with t-BuOOH (TBHP) in n-decane. The compounds are characterized by vibrational spectroscopy, 1H, 13C, and 95Mo NMR spectroscopy, and elementary analysis and are compared to their (η5-C5R5)ReO3 homologues. The Mo−C5R5 force constants have been determined. (η5-C5Bz5)MoO2Cl can be stored and handled at room temperature without decomposition, in contrast to the more temperature sensitive Cp (R = H) and Cp* (R = Me) analogues. The (η5-C5R5)MoO2Cl complexes catalyze the epoxidation of cyclooctene, styrene, and 1-octene with TBHP as oxidizing agent. The highest activity is found for (η5-C5Bz5)MoO2Cl: TOF 21000 mol/(mol × h) for cyclooctene in CH2Cl2 at 55 °C with a ratio catalyst:substrate:TBHP = 0.0001:1:2.5. This activity even surpasses that of the well-known MeReO3/H2O2 system. The stable parent carbonyls (η5-C5R5)Mo(CO)3Cl can be used as catalyst precursors since they ...

The isostructural hexakis(dimethyl sulfoxide)-aluminium(III), -gallium(III) and -indium(III) iodides crystallise in the trigonal space group R (no. 148), Z = 3, at 295 ± 1 K. The metal ions are located in a symmetry site with M–O bond distances of 1.894(4), 1.974(4) and 2.145(3) A, and M–O–S bond angles of 127.1(3), 124.1(3) and 123.1(2)°, for M = Al, Ga and In, respectively. The unit cell parameters are a = 10.762(2), c = 24.599(3) A, V = 2467.2(5) A3 for [Al(OS(CH3)2)6]I3, a = 10.927(2), c = 23.868(4) A, V = 2468.1(6) A3 for [Ga(OS(CH3)2)6]I3, and a = 11.358(2), c = 21.512(4) A, V = 2403.5(7) A3 for [In(OS(CH3)2)6]I3. The increasing compression of the octahedral MO6 coordination entities along one three-fold axis for M = Al, Ga and In, respectively, explains why the largest ion indium(III) has the smallest unit cell volume. EXAFS measurements on the dimethyl sulfoxide solvated gallium(III) and indium(III) ions in solution and in the solid perchlorate and trifluoromethanesulfonate salts, show similar bond distances as in the solid iodide solvates. Raman and infrared spectra have been recorded for the hexakis(dimethyl sulfoxide)metal(III) iodides and the nature of the metal–sulfoxide bond has been evaluated by normal coordinate methods. The symmetric and asymmetric M–O stretching modes correspond to the vibrational frequencies 465 and 540 cm−1 for [Al(OS(CH3)2)6]I3, 491 and 495 cm−1 for [Ga(OS(CH3)2)6]I3, and 444 and 440 cm−1 for [In(OS(CH3)2)6]I3, respectively.