Search

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.

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.

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.

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

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.

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.

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.

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.

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 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.

The structures of the dimeric bispentacyanoplatinate(III)(PtPt) complex [Pt2(CN)10]4- and the pentacyanoplatinum(IV) species [Pt(CN)5(OH)]2-, [Pt(CN)5(H2O)]-, and [Pt(CN)5I]2- have been studied in aqueous solution by the EXAFS technique. A nonsupported Pt−Pt bond, 2.73(1) A, connects two Pt(CN)5 entities in the dimer. Normal coordinate analyses have been made on the basis of the Raman spectra, and the force constants have been used for discussions of the bonding. The metal−metal stretching force constants for the [Pt2(CN)10]4- complex, the [(NC)5Pt−Tl(CN)n]n- (n = 1, 2, and 3) complexes, and some other dimetallic complexes have been correlated with the metal−metal bond distances. In the [Pt(CN)5X]n- complexes, the mean Pt−C bond distance of the pentacyanoplatinum group was found to increase, and the corresponding Pt−C force constants were found to decrease, with increasing donor ability of the ligand X in the order X = H2O, OH, I, and Pt(CN)5. The crystal structures of the compounds Tl2[Pt(CN)5(OH)] and K...

High- and low-oxidation state CpML3-type (M=Mn, Re; L=O, CO) cyclopentadienyl complexes have been investigated by vibrational spectroscopy (FTIR, FT-FIR, FT-Raman) and normal coordinate calculations. The vibrational spectra of CpMn(CO)3, CpRe(CO)3 complexes were revised and reinterpreted. For the oxo-complexes and Cp*-carbonyl compounds, Cp*Mn(CO)3 and Cp*Re(CO)3, a complete spectral assignment is proposed. The results of the normal coordinate analysis are in good agreement with the spectral evidence. The vibrational spectroscopic findings help to explain earlier observations, e.g. the significantly lower stability of CpReO3 in comparison to Cp*ReO3. Characteristic force constants have been determined for Cp and Cp* ligands. A method is described for estimating an approximate force constant for the metal cyclopentadienyl (Cp) ligand bond stretch in half sandwich type of complexes, based on the use of an effective ‘spectroscopic’ mass of the Cp-ligand.

Six compounds of the type [CpMo(CO)3R] (R = Cl (1), CH3 (2), CF3 (3)) and [CpMo(O2)(O)R] (R = Cl (4), CH3 (5), CF3 (6) (Cp = η5-cyclopentadienyl)) have been synthesised and characterised. The crystal structures of [CpMo(CO)3CF3] and [CpMo(O2)(O)CF3] are compared to their literature known chloro and methyl derivatives. The influence of the groups R on the performance as epoxidation catalysts is examined. DFT calculations, IR-spectroscopy and X-ray crystallography help to explain differences in reactivity and enable a rational design of active molybdenum tricarbonyl and oxo-peroxo complexes.

The crystal and molecular structure of a polycrystalline powder with a metal–metal bond and the composition TlPt(CN)5 has been determined by combining results from X-ray powder diffraction (XRD), extended X-ray absorption fine structure (EXAFS) and vibrational spectroscopic studies. The XRD data gave the tetragonal space group P4/nmm (No. 129), with a=7.647(3), c=8.049(3) A, Z=2, and well-determined positions of the heavy metal atoms. The Pt−Tl bond length in the compound is 2.627(2) A. The platinum atom coordinates four equivalent equatorial cyano ligands, with a fifth axial CN ligand and a thallium atom completing a distorted octahedral coordination geometry. The Tl−Pt(CN)5 entities are linked together in linear −NC-Pt-Tl-NC-Pt-Tl chains through the axial cyano ligand. These linear “wires” are the essential structural features and influence the properties of the compound. A three-dimensional network is formed by the four equatorial cyano ligands of the platinum atom that form bridges to the thallium atoms of neighbouring antiparallel chains. The platinum atom and the five nitrogen atoms from the bridging cyano groups form a distorted octahedron around the thallium atom. EXAFS data were recorded at the Pt and Tl LIII edges for a more complete description of the local structure around the Pt and Tl atoms. The excessive multiple scattering was evaluated by means of the FEFF program. Raman and infrared absorption spectroscopy reveal strong coupling of the vibrational modes of the TlPt(CN)5 entities, in particular the metal–metal stretching mode, which is split into four Raman and two IR bands. Factor group theory shows that a structural unit larger than the crystallographic unit cell must be used to assign vibrational bands. Intra- and intermolecular force constants have also been calculated. The compound exhibits red luminescence at 700±3 nm in glycerol and has a corresponding excitation maximum at 240 nm. X-ray photoelectron spectra (XPS) show that the metal atoms have intermediate oxidation states, Pt3.2+ and Tl1.6+, between those in the parent PtII and TlIII species and the decomposition products, PtIV and TlI. The solid compound TlPt(CN)5 is stable to 520 °C. However in presence of water, a two-electron transfer between the metal atoms results in the cleavage of the metal–metal bond at 80 °C, forming a PtIV pentacyanohydrate complex and a monovalent thallium ion.

Structural, electronical and vibrational properties of Cp− and Cp*−, and of alkali metal cyclopentadienyl (CpM, M=Li, Na, K) and pentamethylcyclopentadienyl (Cp*M, M=Li, Na) complexes have been studied. The main goals of the study were to investigate the influence of the CH3 groups on the spectral features and on the MC force constants and the change of ionic character of the MC bond for different metals. FT-IR, FT-FIR and FT-Raman spectra of LiCp* and NaCp* compounds were recorded. Density functional theory calculations have been performed in order to obtain optimized geometries, vibrational frequencies and IR intensities. Calculated vibrational data were systematically compared to the experimental ones. Based on the calculations and experimental data, the vibrational spectra of Cp− and CpM were revised and reinterpreted, and a complete assignment of Cp*− and Cp*Li, Cp*Na vibrations was proposed. Correlations have been determined for the different metal atoms and the charge distribution, bond orders, bond energies and force constants.

FTIR and FT-Raman spectra of [PdCl 3 (C 2 H 4 )] − and [PdCl 3 (C 2 D 4 )] − anions have been recorded at greater sensitivity than hitherto and assigned on the basis of the well-studied Zeise’s salt. Density functional theory (DFT) calculations were performed in order to obtain the optimised geometry, the vibrational frequencies and IR intensities of the Pd-complex. The comparison of the theoretical infrared spectra, the H/D isotopic shifts and the shifts in the CC stretching and CH scissoring frequencies upon coordination with those from experimental study show a remarkable agreement for the [PdCl 3 (C 2 H 4 )] − and [PdCl 3 (C 2 D 4 )] − species. The optimised PdC bond distance is 2.197 A, indicating that the metal–ligand bond is weaker in [PdCl 3 (C 2 H 4 )] − than in Zeise’s salt but C 2 H 4 seems to be more distorted in the Pd-analogue. The calculated force constants also confirm the lower stability of the Pd-complex.

Polymer-supported oxidic osmium catalysts based on cross-linked poly(4-vinyl pyridine) were synthesized by various routes and characterized by a number of physical techniques (Raman, IR, XPS, 13 C and 15 N solid-state NMR spectroscopy). Model compounds of type Os 2 O 6 L 4 (L = pyridine, 4- iso -propyl pyridine, and 4- tert -butyl pyridine) were obtained under the conditions of the catalyst synthesis. The catalytic systems were successful in the dihydroxylation of alkenes.

Carbenes L derived from imidazole and triazole, as generated from the corresponding azolium precursor salts, smoothly react with simple metal carbonyls such as M(CO)6 (M  Cr, Mo, W), Fe(CO)5, and Ni(CO)4 to give the substitution products M(CO)5L, Fe(CO)4L, Ni(CO)3L, and Ni(CO)2L2, respectively, owing to the pronounced C-nucleophilicity of the free carbenes L. Dicarbenes L L form chelate complexes of type M(CO)4( L L ) upon treatment with M(CO)6 (M  Cr, Mo, W). The new bis(carbene)nickel (0) complex Ni(CO)2L2 and the first member of a metal complex M(CO)4( L L ) exhibiting a chelating dicarbene of the triazole series have been characterized by single-crystal X-ray diffraction. It is evident from the present study that heterocyclic mono- and (chelating) dicarbenes of the aza-type are congeners of phosphanes and diphosphanes, resp., with regard to their metal-coordination chemistry. Both in terms of ligand properties and metal complex synthesis, they closely resemble electron-rich phosphanes, e.g. trimethylphosphane.

The strongly hydrogen bonded species (CH3)2SO...H3O+ formed in concentrated hydrochloric acid displays a new low energy feature in its sulfur K-edge X-ray absorption near edge structure (XANES) spectrum. Density Functional Theory-Transition Potential (DFT-TP) calculations reveal that the strong hydrogen bonding decreases the energy of the transition S(1s) --LUMO, which has antibonding sigma*(S-O) character, with about 0.8 eV. Normal coordinate force field analyses of the vibrational spectra show that the SO stretching force constant decreases from 4.72 N cm(-1) in neat liquid dimethyl sulfoxide to 3.73 N cm(-1) for the hydrogen bonded (CH3)2SO...H3O+ species. The effects of sulfur coordination on the ambidentate dimethyl sulfoxide molecule were investigated for the trans-Pd((CH3)2SO)2Cl2, trans-Pd((CD3)2SO)2Cl2 and cis-Pt((CH3)2SO)2Cl2 complexes with square planar coordination of the chlorine and sulfur atoms. The XANES spectra again showed shifts toward low energy for the transition S(1 s) --LUMO, now with antibonding sigma*(M-Cl, M-S) character, with a larger shift for M = Pt than Pd. DFT-TP calculations indicated that the differences between the XANES spectra of the geometrical cis and trans isomers of the M((CH3)2SO)2Cl2 complexes are expected to be too small to allow experimental distinction. The vibrational spectra of the palladium(II) and platinum(II) complexes were recorded and complete assignments of the fundamentals were achieved. Even though the M-S bond distances are quite similar the high covalency especially of the Pt-S bonds induces significant increases in the S-O stretching force constants, 6.79 and 7.18 N cm(-1), respectively.

Detailed infrared and Raman studies are reported for [PtCl3(12C16O)]−, [PtCl3(13C16O)]−, [PtCl3(12C18O)]−, and [PtCl3(14C16O)]− together with assignments. Bands observed for the 14C16O species at 2005, 483, 507, and 466 cm−1 are assigned to CO and PtC stretching, PtCO in-plane and out-of-plane linear bending modes, respectively. Force constants have been calculated using a modified valence force field, with constrained off-diagonal force constants based on [PtCl4]2− and [PtX3(CO)]− (X = Br, I). The effective G-matrix method (EGM) has been used for approximate calculation of CO and PtC stretching force constants for some other square-planar platinum–carbonyl complexes. The results are discussed with the assistance of stretching force constants for some of the simpler complexes. Key words: vibrational spectra, force constant calculation, 13C, 14C, and 18O labelled [PtCl3(CO)]−.

The infrared emission spectra of CO adsorbed on alumina-supported 1, 3, and 5 wt % Rh, Ir, and Pt metal-containing catalysts were studied at 423 and 473 K. While CO is adsorbed in dicarbonyl (dimer), linearly (on-top) bonded and bridged carbonyl forms on rhodium and platinum, the dimer form is dominant on iridium. The relative intensity of Rh-CO and Ir-CO linear bands decrease with increasing temperature compared to the intensity of the dicarbonyl bands; the corresponding bands on Pt behave the opposite way. Two dicarbonyl and two linear Pt-CO bands were identified in the infrared spectra of Pt/Al 2 O 3 catalysts. The surface structure (kinked or planar Pt atoms), the dispersity of the metal, the temperature, and the quantity of adsorbed CO on the surfaces all have an effect on the fine structure of the Pt-CO stretching bands. The metal-carbon and CO stretching force constants were calculated for surface dicarbonyl, linearly bonded CO, and bridged carbonyl species. The metal-carbon stretching wavenumbers and force constants were predicted and compared between surface species and metal carbonyl complexes. The iridium-carbon bonds were found always stronger than the Rh-C and Pt-C ones in all surface species. The observed stretching wavenumbers and force constants seem to support the idea that CO and metal-carbon bonds are always stronger in metal carbonyl complexes than in adsorbed surface species. The distribution and mode of CO adsorption on surface metal sites can be effectively studied by means of infrared emission spectroscopy.

The in vivo and in vitro effects of Cd2+ and the CYP1A inductor beta-naphthoflavone(beta-NF) on the hepatic cytochrome P450 (Cyt 450) monooxygenases were studied in silver carp (Hypophthalmichtys molitrix V.), wels (Silurus glanis L.), and carp (Cyprinus carpio). In vivo treatment of carp with a high dose of Cd2+ (10 mg kg(-1), for 3 days) caused a strong inhibition of 7-ethoxyresorufin-O-deethylase (EROD) and a lower inhibition of 7-ethoxycoumarin-O-deethylase (ECOD) activity. The low-dose cadmium treatment (2 mg kg(-1) Cd2+, for 6+3 days) resulted in 4-fold increase in EROD and a 3-fold increase in ECOD activity. The combined treatment with Cd2+ and beta-NF in both cases led to a loss of EROD inducibility. The silver carp and wels were treated with 10 mg L(-1) Cd2+ for 72 h in water. The Cyt P450 content in the wels liver microsomes was increased significantly after treatment for 48 h, whereas there was only a slight, not significant increase in Cyt P450 content in the silver carp microsomes. While the Cd2+ treatment resulted in inhibition of the CYP1A isoenzymes (EROD and ECOD), the APND (aminopyrene-N-demethylase, CYP2B or CYP3A isoenzyme) activity was increased 3- to 4-fold in both fish species. In vitro experiments of the effect of Cd2+ led to a concentration-dependent inhibition in all three investigated fish species. The ECOD isoenzyme of silver carp was the most sensitive to Cd2+. The lowest concentration of Cd2+ resulted in 50% inhibition. The APND isoenzyme was similarly sensitive to Cd2+ in all three investigated fish species. The most sensitive species was the wels, and the least sensitive were the carp isoenzyme. FTIR spectroscopy confirmed that cadmium caused damage to the protein structure. These results support the enzyme activity measurements measured in vivo and in vitro.

Fourier-transform infrared (FTIR) spectroscopy has been applied to the study of mainstream cigarette smoke from cigarettes of different stated strengths (regular and various light cigarettes with different reported nicotine, tar and CO contents). This technique has allowed for the measurement of a variety of gaseous components including hydrocarbons and both nitrogen and carbon oxides. The results demonstrate that the strength of the cigarette does not have a significant bearing on the quantity of the observed components produced. Additionally, open-path FTIR studies of diluted sidestream and exhaled smoke have been conducted. These measurements revealed that the majority of gaseous pollutants originated from the sidestream smoke, while the primary smoke was 'purified' or diluted upon exhalation by the smoker.

Trimethylsilyl derivatives of 10 different hydroxy- and methoxyhydroxyflavonoid compounds were studied by the GC-FTIR technique. Optimal deviation parameters were determined for the flavonoids studied. The correlation found between retention and gas-phase IR data can successfully be used in structural identification of compounds having very similar chromatographic behaviour. The shift of the carbonyl frequency gives information on the presence of substituting agents.

A highly selective and efficient oxidation of sulfides to sulfoxides is presented. The reactions were carried out at room temperature in the absence of a catalyst in the ionic liquid [Bmim][BF4] (Bmim = 1-butyl-3-methylimidazolium) using aqueous H2O2 (35%) as oxidant. The products were obtained in high yields. Compared to the analogous reactions in organic solvents, this system can be recycled without significant loss of activity and selectivity. Additionally, the reaction mechanism was examined by IR, Raman and NMR spectroscopy. Based on these examinations, it appears that the crucial step during the oxidation procedure is the formation of a hydrogen bond between the ionic liquid and the oxidant.

The IR and Raman spectra of [Pt(C2H4)3], [Pt(C2D4)3] and IR spectra of [Ni(C2H4)3] are reported and assignments proposed. Comparisons are made with previously reported IR spectroscopic features of Pd, Co and Cu analogues. The results of a CNDO/2 geometry optimization calculation for [Ni(C2H4)3] are summarized, and reveal closely similar structural parameters for the ethylene ligand to those established for the Pt complex. Some comparisons are made between vibrational frequencies of the complexes and those of ethylene chemisorbed on single crystal metal surfaces.

The results of force constant calculations of systems Hg(CH3)X = CH3, Cl, Br, I, CN, SCH3 and {As(CH3)3}+) are briefly reviewed and the importance of data compatibility in comparative studies is stressed. Aspects of relationships between the force constants and other physical properties are discussed, but outside the limited series X = Cl, Br or I do not appear to be of fundamental significance.

Adsorption of cyclohexanol on Pt SiO 2 catalyst was investigated by means of ir spectroscopy. At room temperature hydrogen atoms from both OH and tertiary carbons split off easily, resulting in the formation of cyclohexanone held on SiO 2 by hydrogen bonds whereas on Pt it is held by a π-bond or through the lone electron pair of oxygen. Dissociation of α-hydrogens in cyclohexanone commences only at circa 353 K. At 393 K bands characteristic of an enolic system were observed, suggesting formation of a π-oxoallylic species during dehydrogenation of cyclohexanone.

The nature of the bond between a metal and an unsaturated hydrocarbon is one of the most fundamental and significant problems in coordination chemistry. In spite of wide structural and spectroscopic studies of olephinic n-complexes a number of fundamental spectroscopic properties have not been clearified yet. Reinvestigation of FT-IR and Raman spectra of K(Pt(C H )C13) and K(Pt(C2H4)C13) .H20 in both the solid phase and $ater/HCl solution suggests some modification of widely accepted assignments. Skeletal modes of (NBu4)(Pt(C2H4)Br 1, (NBu4)(Pd(C H4)C13) and their

The vibrational spectra data, the assignments, and the results of normal coordinate calculations for CH 4 − n (HgCH 3 ) n molecules (2 ⩽ n ⩽ 4) are reported. The central CHg valence force constants are 1.870, 1.653, and 1.582 N cm −1 while the terminal ones are 2.121, 2,101, and 2.160 N cm −1 for n = 2, 3 and 4, respectively. The latter values are 12, 21, and 27% higher than the central CHg force constants, but all of them are substantially lower than those in dimethylmercury (2.379 N cm −1 ). These findings can be accounted for in terms of increasing shift of electron density towards the periphery of these molecules and increasing non-bonded metal-metal interaction. The nature of the normal modes is discussed.

Force constants of [Hg(CF 3 ) 2 ], [Hg(CCl 3 ) 2 ], [Hg(CF 3 )X] (X = Cl, Br, or I) and [Hg(CCl 3 )X] (X = Cl or Br) have been calculated using a valence force field and wavenumber data from solutions. The potential energy distributions show substantial mixing between the symmetrical stretching and umbrella deformation coordinates of the trihalomethyl groups. The high degree of mixing of HgC and HgX stretching coordinates in [Hg(CF 3 )Br] and [Hg(CF 3 )I] accounts for the discontinuous frequency and intensity trends in the [Hg(CF 3 )X] series. The results are discussed in comparison with methylmercury and other trifluoromethyl systems.

Impregnation of Fe3(CO)12 on Cab-O-Sil has been studied by ir spectroscopy, Mossbauer spectroscopy, and mass spectrometry. Isotope exchange between CO ligands of the impregnated sample and gas phase CO molecules was also investigated. On impregnation, two types of interaction can be distinguished: (i) interaction of the type FeCO…HOSi and CO…HOSi, shown by the shift to lower and higher ir frequencies for bridged and for terminal CO, respectively, and (ii) interaction between the metal framework and the support revealed in the oxidation of iron to form very small iron oxide particles. On impregnation a small amount of CO is evolved as a result of the interaction. CO exchange occurs faster with alumina-supported clusters than with silica-supported samples. On decomposition up to 370 K, the metal framework is retained and the cluster structure can be partly restored in a CO atmosphere. Above 420 K, Fe3(CO)12 is decomposed to form Fe2+ oxide on the surface. A possible mechanism for impregnation is discussed in terms of electron donation from the support oxygen to the iron d-bands as a result of which the metal-carbon bond strength is influenced. On decomposition the metallic iron interacts with the support OH groups causing oxidation and Fe2+ formation.

Vibrational assignments for Hg(C 2 H 5 )X (X  Cl, Br or I) and HgBr(C 2 D 5 ) are proposed, on the basis of solution studies as far as possible. For the bromides, 21 force constants are refined in the presence of 12 constrained values from C 2 H 5 Cl and 12 of these are used as additional constraints in refining 9 force constants for the chloride and iodide. The nature of the normal modes of Hg(C 2 H 5 )C1 is discussed. The Hg-C stretching force constants of the ethyl compounds is marginally higher than in corresponding methyl derivatives.

The vibrational frequencies of the tetrakis(amminemercurio)methane cation, [C(HgNH 3 ) 4 ] 4+ ( 1 ), in both aqueous ammonia buffer solutions and in solid [C(HgNH 3 ) 4 ](PF 6 ) 4 have been used in an all-atom normal coordinate analysis for 1 . A similar analysis has been carried out for the isoelectronic tetrakis(methylmercurio)methane, C(HgCH 3 ) 4 ( 2 ). 1 and 2 respectively exhibit the highest (2.016 N/cm) and lowest (1.509 N/cm) valence force constants K (C-Hg) in the central CHg 4 entity so far observed for tetramercuriomethanes. The force constants for the peripheral Hg-NH 3 and Hg-CH 3 bonds in 1 and 2 are 2.461 N/cm and 2.183 N/cm, respectively. Both the electronic properties of the peripheral ligands and the total charge on the molecule are shown to influence the force constants. The potential energy distributions indicate that the valence vibrations of the N-H/C-H and Hg-NH 3 /Hg-CH 3 bonds in 1 and 2 , and the breathing vibrations of the central CHg 4 units are almost independent of all other vibrations, which in turn are more or less strongly coupled.

The behavior of Ru 3 (CO) 12 (I), H 2 Ru 3 Fe(CO) 12 (II), a 1:1 Ru 3 (CO) 12 and Fe 3 (CO) 12 mixture (III), RuFe 2 (CO) 12 (IV), and Fe 3 (CO) 12 (V) deposited on Cab-O-Sil HS-5 has been compared. (III) and (V) have been studied by Mossbauer spectroscopy and by ir-spectroscopy, and (I)-(V) by temperatureprogrammed decomposition (TPDC) and temperature-programmed reduction (TPR). Decomposition, which is faster in hydrogen than in helium or in vacuum, and is reversible below 400 K, is normally faster for (V) than for (I). At low temperature, CO ligands leave the metal carbonyl cluster (MCC) in one step for (V), whereas they are decomposed stepwise via the formation of subcarbonyl species for (I). In this range the formation of Ru 3 (CO) 3 species has been verified. On decomposition of (V), there is some CO adsorption, as indicated by ir spectroscopy and low catalytic activity. This increases when decomposition occurs in helium, and is attributed to the smaller particles stabilized by the metal-carbon species, formed from CO during the decomposition. For (I), decomposition results in a slight oxidation, indicated by weak ir bands in the range of 2100–2140 cm −1 . Interaction between Fe and Ru in (III) does not occur in the impregnated phase, but develops during the decomposition, which starts with Fe 3 (CO) 12 decomposition and thereby influences the decomposition of Ru 3 (CO) 12 . However, reduction of iron is also facilitated by the presence of ruthenium, as indicated by Mossbauer spectroscopy. The general feature revealed during decomposition in helium, i.e., the increase of surface carbon, is also operative here, and thus the dispersion of the metal is higher than for decomposition in hydrogen. The mechanism of the decomposition is discussed in terms of the formation of subcarbonyl species for Ru-containing samples and the formation of surface carbon is also considered. The mechanism and possible reaction pathways are given.

A study of the vibrational spectra of PhHgX (X = Cl, Br and I), Ph2Hg and (C6D5)2Hg is reported. A normal coordinate analysis has been performed for in-plane vibrations of PhHgX. The characteristic frequency ranges for the aromatic ring are given for the phenyl derivatives of mercury.

Force constants of dimethylmercury are calculated using the vibrational frequencies of gaseous (CH 3 ) 2 Hg and (CD 3 ) 2 Hg. A force constant calculation utilizing the generalised inverse matrix procedure is discussed briefly. Assuming a free rotational model, the force field is introduced as a trigonometrical function of the torsional angle γ; the time variant corrections of vibrational frequencies and normal coordinate vectors which this involves are investigated.

A study of organomercury compounds is reported. The IR and Raman spectra were measured and frequency assignments are made for 21 compounds. The characteristic frequencies of the -CH 2 HgX and the -CH 2 HgCH 2 -groups were determined and inferences are made on the molecular structure. Normal coordinate analysis was performed for diethylmercury, allylmercury chloride, allylmercury bromide, dibenzylmercury and benzylmercury chloride, bromide and iodide. The force constants in the environment of the Hg atom were refined by the least-squares method. It was found that the force constants of the C-Hg stretching vary in the range from 2.53 to 2.67 mdyn/A.