Trapping of Terminal Platinapolyynes by Copper(I) Catalyzed Click Cycloadditions; Probes of Labile Intermediates in Syntheses of Complexes with Extended sp Carbon Chains,and Crystallographic Studies

The silylated hexatriynyl complex trans-(C₆F₅)(p-tol₃P)₂Pt(C≡C)₃SiEt₃ ( PtC₆TES ) is converted in situ to PtC₆H (wet n-Bu₄N⁺ F⁻, THF) and cross coupled with the diyne H(C≡C)₂SiEt₃ ( HC₄TES ; CuCl/TMEDA, O₂) to give PtC₁₀TES (71 %). This sequence is repeated twice to afford PtC₁₄TES (65 %) and then PtC₁₈TES (27 %). An analogous series of reactions starting with PtC₈TES gives PtC₁₂TES (60 %), then PtC₁₆TES (43 %), and then PtC₂₀TES (17 %). Similar cross couplings with H(C≡C)₂Si(i-Pr)₃ ( HC₄TIPS ) give PtC₁₂TIPS (68 %), PtC₁₄TIPS (68 %), and PtC₁₆TIPS (34 %). The trialkylsilyl species (up to PtC₁₈TES ) are converted to 3+2 “click” cycloadducts or 1,4-disubstituted 1,2,3-triazoles trans-(C₆F₅)(p-tol₃P)₂Pt(C≡C)_n-1C=CHN(CH₂C₆H₅)N=N (29–92 % after workups). The most general procedure involves generating the terminal polyynes PtC _x H (wet n-Bu₄N⁺ F⁻, THF) in the presence of benzyl azide in DMF and aqueous CuSO₄/ascorbic acid. All of the preceding complexes are crystallographically characterized and the structural and spectroscopic properties analyzed as a function of chain length. Two pseudopolymorphs of PtC₂₀TES are obtained, both of which feature molecules with parallel sp carbon chains in a pairwise head/tail packing motif with extensive sp/sp van der Waals contacts.     

The Reactive Sites of Methane Activation: A Comparison of IrC3+ with PtC3+

The activation reactions of methane mediated by metal carbide ions MC₃⁺ (M = Ir and Pt) were comparatively studied at room temperature using the techniques of mass spectrometry in conjunction with theoretical calculations. MC₃⁺ (M = Ir and Pt) ions reacted with CH₄ at room temperature forming MC₂H₂⁺/C₂H₂ and MC₄H₂⁺/H₂ as the major products for both systems. Besides that, PtC₃⁺ could abstract a hydrogen atom from CH₄ to generate PtC₃H⁺/CH₃, while IrC₃⁺ could not. Quantum chemical calculations showed that the MC₃⁺ (M = Ir and Pt) ions have a linear M-C-C-C structure. The first C–H activation took place on the Ir atom for IrC₃⁺. The terminal carbon atom was the reactive site for the first C–H bond activation of PtC₃⁺, which was beneficial to generate PtC₃H⁺/CH₃. The orbitals of the different metal influence the selection of the reactive sites for methane activation, which results in the different reaction channels. This study investigates the molecular-level mechanisms of the reactive sites of methane activation.     

Competitive Activation of C?H and C?X Bonds in Reactions of Pt+ with CH3X (X=F,Cl): Experiment and Theory

The reactions of Pt⁺ with CH₃X (X=F, Cl) are studied experimentally by employing an inductively coupled plasma/selected‐ion flow tube tandem mass spectrometer and theoretically by density functional theory. Dehydrogenation and HX elimination are found to be the primary reaction channels in the remarkably different ratios of 95:5 and 60:40 in the fast reactions of Pt⁺ with CH₃F and CH₃Cl, respectively. The observed kinetics are consistent with quantum chemistry calculations, which indicate that both channels in the reaction with CH₃F are exothermic with ground‐state Pt⁺(²D), but that HF elimination is prohibited kinetically because of a transition state that lies above the reactant entrance. The observed HF‐elimination channel is attributed to a slow reaction of CH₃F with excited‐state Pt⁺(⁴F) for which calculations predict a small barrier. The calculations also show that both the HCl‐elimination and dehydrogenation channels observed with CH₃Cl are thermodynamically and kinetically allowed, although the state‐specific product distributions could not be ascertained experimentally. Further CH₃F addition is observed with the primary products to produce PtCH₂⁺(CH₃F)_1,2 and PtCHF⁺(CH₃F)_1,2. With CH₃Cl, sequential HCl elimination is observed with PtCH₂⁺ to form PtC_nH_2n⁺ with n=2, 3, which then add CH₃Cl sequentially to form PtC₂H₄⁺(CH₃Cl)_1–3 and PtC₃H₆⁺(CH₃Cl)_1,2. Also, sequential addition is observed for PtCHCl⁺ to form PtCHCl⁺(CH₃Cl)_1,2.     

Pentamethylcyclopentadienylplatinum(IV) complexes

Reaction of dichloro(η⁴-pentamethylcyclopentadiene)platinum with bromine yields a η⁵-pentamethylcyclopentadienylplatinum(IV) complex which is formulated as [C₅Me₅PtBr₃PtC₅Me₅]Br₃.     

Zur Synthese und Kristallstruktur der ternären Carbide Na2PdC2 und Na2PtC2

Syntheses and Crystal Structures of Ternary Carbides Na₂PdC₂ and Na₂PtC₂ Na₂PdC₂ and Na₂PtC₂ were synthesized by the reaction of sodium carbide with palladium and platinum respectively. The crystal structures could be solved from X-ray powder diffraction data (space group: P3 m1, Z = 1). Both compounds crystallize in a new structure type with [M(C₂)_2/2^2?] chains (M?Pd, Pt) as the characteristic structural unit. The existence of a C? C triple bond was confirmed by Raman spectroscopy.     

Controlled emission of platinum(II) terpyridyl complexes with poly-l-glutamic acid

Poly-l-glutamic acid, P(Glu), bearing multiple negatively charged side chains served as a polymeric spatially aligned scaffold for the aggregation of positively charged platinum(II) complexes [Pt(trpy)CCR](OTf) (trpy = 2,2′,6′,2″-terpyridine; R = Ph (PtH), PhC₁₂H₂₅-p (PtC₁₂)) through electrostatic interaction, resulting in tunable emission properties. PtC₁₂ was found to exhibit gradual increase in the emission intensity based on the triplet metal-metal-to-ligand charge transfer (³MMLCT) in a tris/HCl buffer (pH 7.6)/MeOH (v/v = 1/14) solution with concomitant decrease in the emission intensity based on the triplet metal-to-ligand charge transfer (³MLCT)/the triplet ligand-to-ligand charge transfer (³LLCT) as the amount of P(Glu) was increased. Such synergistic effect was not observed in the case of PtH, wherein the emission intensity based on ³MLCT/³LLCT was increased by the increase in the amount of P(Glu), indicating that alkyl long chain of PtC₁₂ is considered to play an important role in the aggregation of the platinum(II) terpyridyl moieties to show Pt(II)-Pt(II) and π-π interactions.     

Kinetics and Mechanism of the Reaction of Chloroplatinum(II) Complexes with Alkyl Radicals

The reaction between certain platinum(II) complexes and alky radicals produces an unstable organoplatinum(III) intermediate, {Pt^III -R}. The kinetics of this step were evaluated by laser flash photolysis with ABTS² (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) ion) and TMPD (tetramethylphenylenediamine) as kinetic probes. The rate constants for PtCl₄^2? are: k_Pt/10⁸ L mol^?1 s^?1 = 5.2, 2.8 and 0.27 for CH_3, C₂H₅, and CH₂Cl in aqueous solution at pH 1. Those with cis-Pt(NH₃)₂Cl₂ are somewhat smaller, and those for Pt(NH₃)₄²⁺ too small to measure will) this technique. The product analysis indicates that the decomposition of organoplatinum takes place by hydrolysis and (for R = C₂H₅ only) by β-elimination, The kinetic isotope effect on die β-elimination of DCH₂CH₂PtC₄,^2? is k_H/k_D = 1.2. The β-elimination step produces a Pt^III-hydride that releases hydrogen gas and forms {Pt_III-OH}. The short-lived Pt(III) intermediate may disproportionate or oxidize the Co^II complex that is produced in the radical-generating step.     

Characteristic Features of Platinum Stereochemistry in the Structures of Organometallic Compounds

The Voronoi-Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to carry out crystal chemical analysis of 85 compounds containing 124 PtC _n or PtC _n Pt _m coordination polyhedra in which the Pt-C and Pt-Pt bond lengths vary in the 1.82-2.43 and 2.58-2.98 Å ranges. The main stereochemical features of platinum are discussed depending on the nature (C or Pt) and the number (n varying from 1 to 10; m varying from 0 to 9) of atoms in the first coordination sphere. It is shown that the VDP parameters can be used to identify the aghostic Pt···H-C interactions in the crystal structure.     

Mechanism of Ethylene Migratory Insertion and Dimerization Catalyzed by δ‐Alkyl Platinum Complexes–A DFT Study

The mechanism of ethylene insertion reactions catalyzed by cationic δ‐alkyl platinum complexes has been studied at the B3LYP level of density functional theory. The initial steps of the reactions proceed via the coordination of ethylene to the reactants L₂Pt(II)R⁺, where L₂=none, (NH₃)₂, (CHNH)₂; R=H, CH₃, C₂H₅ in which ethylene coordinates strongly to the complexes PtCH⁺₃ and PtC₂H⁺₅ (coordination energies (CE) are 296.52 and 229.28 kJ/mol, respectively), while nitrogen‐containing ligands decrease the energies: Pt(NH₃)₂CH⁺₃ (CE: 180.04 kJ/mol), Pt(NH₃)₂C₂H⁺₅ (CE: 97.86 kJ/mol), Pt(CHNH)₂CH⁺₃ (CE : 176.31 kJ/mol) and Pt(CHNH)₂C₂H⁺₅ (CE: 91.00 kJ/mol). Moreover, ethylene insertion into the Pt‐alkyl bond, which is the rate‐determining step, is endothermic with barrier heights for L₂PtCH₃(C₂H₄)⁺ decreasing in the order: PtCH⁺₃ (164.18 kJ/mol)>(NH₃)₂ PtCH⁺₃ (129.95 kJ/mol)>(CHNH)₂ PtCH⁺₃ (115.27 kJ/mol), which has the same tendency for the ethyl case. The insertion product will continually undergo β‐hydride elimination, which is exothermic. On the other hand, the effects of solvent (dichloromethane, THF and benzene) are investigated with PCM method, but the inclusion of the effects in the computations only slightly affects the results. Beside that, a complete catalytic cycle for ethylene dimerization is studied in detail and the calculations agree well with known energetic and recognized tendencies.     

Spectra and structure of gallium compounds: Part VI. Infrared and Raman spectra of trimethylgalliumtrimethylphosphine

The infrared (50–4000 cm^?1 ) and Raman (50–3500 cm^?1) spectra of (CH₃)₃GaP(CH₃)₃ have been recorded for the solid state at the temperature of boiling liquid nitrogen. The spectra have been interpreted on the basis of C_3v molecular symmetry and a complete vibrational assignment except for the methyl torsional modes is presented. A modified valence force field model has been utilized in calculating the frequencies and potential energy distribution. The calculated potential constants for the adducts are compared to those previously reported for the Lewis acid and the Lewis base moieties and the differences are shown to be consistent with structural changes upon adduct formation. Extensive coupling has been observed between the Ga-P stretching mode and the PtC₃ and GaC₃ deformational modes. Substantial coupling is also observed between the PC₃ and the GaC₃ rocking motions. The magnitude of the Ga-P stretching force constant is found to be much smaller (0.88 mdyn Å^?1) than that reported for (CH₃)₃PGaH₃ and the difference possibly reflects the relative stabilities of the donor-acceptor bond in the two complex species.The fact that none of the A, modes appear as doublets in the spectra, nor are any of the E modes split except for the GaC₃ antisymmetric stretch, which is believed to be due to the two isotopes of gallium, indicates that there is only one molecule per primitive cell sitting on a C_3v or C₃ site. A rhombohedral space group such as R3m(C⁵_3v) is consistent with these observations.     

Oxidation of methanol on Pt(Mo) electrodes obtained using galvanic displacement method

The electrocatalytic Pt-Mo system was obtained by formation of platinum particles on the Mo surface under its contact with PtC₆²⁻ (PtCl₄²⁻) under the open circuit conditions. Cyclic voltammograms of the obtained Pt(Mo) electrodes feature well pronounced peaks of hydrogen adsorption and desorption on Pt particles. Nonuniform platinum distribution across the electrode surface was found. Pt(Mo) electrodes showed a higher specific activity in the reaction of methanol oxidation in the potential range of 0.35–0.45 V (RHE) as compared to Pt/Pt.     

Platin(0)‐Komplexe mit amino‐substituierten Alkinen: Neue Metallorganische Bausteine für supramolekulare Architekturen und „Kristall‐Engineering”︁

Platinum(0) Complexes with Amino‐Substituted Alkynes: Novel Organometallic Building Blocks for Supramolecular Architectures and “Crystal Engineering” Homoleptic Bis(alkyne)platinum(0) compounds containing either NH₂‐ or NH₂‐/OH‐substituents are formed by reaction of Pt(cod)₂ with alkynes as stable compounds. They can be used as variable building blocks for supramolecular networks. The crystal structure analyses of Bis(2‐amino‐2,5dimethyl‐5‐hydroxy‐hex‐3‐yne)platinum(0) ( 1 ) and of Bis(1(3‐amino‐3‐methyl‐but‐1‐inyl)‐cyclohexane‐1‐ol)platinum(0) ( 2 ) exhibit that the low‐valent Pt atom is tetrahedrally surrounded by the four sp‐hybridizated carbonatoms of the alkynes. Despite the fact that the bond lengths and ‐angles of the PtC₄ units are equal, the supramolecular structures are different. While in 1 polymer strands are formed in which the bis(alkyne)‐Pt⁰ units are connected by (OH)₂(NH₂)₂‐ tetrahedrons, 2 yields only a dimer containing a network of four OH‐ and two NH₂‐groups. Platinum(0) complexes with cationic alkynes bearing ammonium substituents can be isolated as thermal stable compounds. The X‐ray structures of [Cl( FH ⁺)Pt(cod)]₄ ( 8 ) reveals that four molecular units form a cube with both four NH₃⁺ groups and Cl^– at the corners connected by hydrogen bridges. In the bis(alkyne)Pt⁰ complex [Cl_1.5( FH ⁺)_1.5( F )_0.5Pt] ( 9 ) only 1,33 of two NH₂ groups are protonated and a hydrogen bridged network connects four bis(alkyne)Pt⁰ units (cod: cycloocta‐1.5‐diene, F : 1‐(trimethylsilylethinyl)‐1‐amino‐cyclohexane).     

Syntheses and Crystal Structures of BaAgTbS3, BaCuGdTe3, BaCuTbTe3, BaAgTbTe3, and CsAgUTe3

Five new quaternary chalcogenides of the 1113 family, namely BaAgTbS₃, BaCuGdTe₃, BaCuTbTe₃, BaAgTbTe₃, and CsAgUTe₃, were synthesized by the reactions of the elements at 1173–1273 K. For CsAgUTe₃ CsCl flux was used. Their crystal structures were determined by single‐crystal X‐ray diffraction studies. The sulfide BaAgTbS₃ crystallizes in the BaAgErS₃ structure type in the monoclinic space group C³,_2h‐C2/m, whereas the tellurides BaCuGdTe₃, BaCuTbTe₃, BaAgTbTe₃, and CsAgUTe₃ crystallize in the KCuZrS₃ structure type in the orthorhombic space group D¹_,2⁷_,h‐Cmcm. The BaAgTbS₃ structure consists of edge‐sharing [TbS₆^9–] octahedra and [AgS₅^9–] trigonal pyramids. The connectivity of these polyhedra creates channels that are occupied by Ba atoms. The telluride structure features ²_∞[MLnTe₃^2–] layers for BaCuGdTe₃, BaCuTbTe₃, BaAgTbTe₃, and ²_∞[AgUTe₃^1–] layers for CsAgUTe₃. These layers comprise [MTe₄] tetrahedra and [LnTe₆] or [UTe₆] octahedra. Ba or Cs atoms separate these layers. As there are no short Q ··· Q (Q = S or Te) interactions these compounds achieve charge balance as Ba²⁺M⁺Ln³⁺(Q^2–)₃ (Q = S and Te) and Cs⁺Ag⁺U⁴⁺(Te^2–)₃.     

Zum Aufbau der Systeme U-Pd-C,U-Pt-C und Th-Pd-C

Zusammenfassung Isotherme Schnitte zeigen, dass die ternären Systeme U-Pd-C und Th-Pd-C in ihrem Aufbau sehr ähnlich sind. Die Verbindungen der binären Randsysteme bestimmen die Phasengleichgewichte. Bei 1300° C bzw. 1100° C bilden Ordnungsphasen UPd₃ bzw. ThPd₃ Zweiphasengleichgewichte mit UC, U₂C₃ und Kohlenstoff bzw. ThC, ThC₂ und Kohlenstoff. Im System U-Pt-C ist bei 1300° C ein ternäres Carbid U₂PtC₂, das sich peritektisch bildet, mit UC, U₂C₃, UPt₃ UPt₂ und Kohlenstoff im Gleichgewicht.

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Phase Equilibria in the Systems U-Pd-C, U-Pt-C, and Th-Pd-C

Isothermal sections show that the phase relations in the ternary systems U-Pd-C and Th-Pd-C are similar. The compounds of the binary systems determine the phase equilibria. At 1300° C for UPd₃ and 1100° C for ThPd₃, these ordered phases form two-phase equilibria with UC, U₂C₃ and carbon or ThC, ThC₂ and carbon. In the U-Pt-C system at 1300° C a ternary carbide U₂PtC₂, which is formed peritectically is in equilibrium with UC, U₂C₃, UPt₃, UPt₂ and carbon.

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Mit 10 Abbildungen

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Herrn Prof. Dr.H. Nowotny gewidmet.     

Synthesis, photophysical and electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine functionalized cyclometalating ligands

Four cyclometalated Pt(II) complexes, i.e., [(L²)PtCl] (1b), [(L³)PtCl] (1c), [(L²)PtCCC₆H₅] (2b) and [(L³)PtCCC₆H₅] (2c) (HL² = 4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-2,2′-bipyridine and HL³ = 4-[p-(N,N′-dibutyl-N′-phenyl)phenylene-diamino]-phenyl-6-phenyl-2,2′-bipyridine), have been synthesized and verified by ¹H NMR, ¹³C NMR and X-ray crystallography. Unlike previously reported complexes [(L¹)PtCl] (1a) and [(L¹)PtCCC₆H₅] (2a) (HL¹ = 4,6-diphenyl-2,2′-bipyridine), intense and continuous absorption bands in the region of 300-500 nm with strong metal-to-ligand charge transfer (¹MLCT) (dπ(Pt) → π^∗(L)) transitions (ε ∼ 2 × 10⁴ dm³ mol⁻¹ cm⁻¹) at 449-467 nm were observed in the UV-Vis absorption spectra of complexes 1b, 1c, 2b and 2c. Meanwhile, with the introduction of electron-donating arylamino groups in the ligands of 1a and 2a, complexes 1b and 2b display stronger phosphorescence in CH₂Cl₂ solutions at room temperature with bathochromically shifted emission maxima at 595 and 600 nm, relatively higher quantum yields of 0.11 and 0.26, and much longer lifetimes of 8.4 and 4.5 μs, respectively. An electrochromic film of 1b-based polymer was obtained on Pt or ITO electrode surface, which suggests an efficient oxidative polymerization behavior. An orange multilayer organic light-emitting diode with 1b as phosphorescent dopant was fabricated, achieving a maximum current efficiency of 11.3 cd A⁻¹ and a maximum external efficiency of 5.7%. The luminescent properties of complexes 1c and 2c are dependent on pH value and solvent polarity, which is attributed to the protonation of arylamino units in the C^N^N cyclometalating ligands.     

The crystal and molecular structure of dicarbonylbis(diphenylethylphosphine) platinum(0) Pt(CO)2[P(C6H5)2(C2H5)]2

The complex dicarbonylbis(diphenylethylphosphine)platinum, Pt(CO)₂[P(C₆H₅)₂(C₂H₅)]₂, crystallizes in either of the enantiomorphous space groups P3₁21 (No. 152) and P3₂21 (No. 154) with cell dimensions a = 10.64(1), c = 22.06(1) Å, U = 2163 ų; p_c = 1.564 g/cm³ for Z = 3, p_m = 1.55(3) g/cm³. The intensities of 1177 independent reflections have been determined by counter methods with MoKα monochromatized radiation. The structure has been solved by the heavy atom method. The refinement, carried out by full-matrix least squares down to a final R factor of 0.042, has enabled the absolute configuration of the crystal sample (space group P3₁21) to be ascertained. The molecule is roughly tetrahedral, and has the metal atom lying on a two-fold axis of the cell. Bond parameters are: PtC = 1.92(2) Å, PtP = 2.360(4) Å, CPtC = 117(1)° and PPtP = 97.9(2)°. The PtC₂ and PtP₂ moieties make a dihedral angle of 86.0(3)°. The overall C₂ symmetry of the molecule is probably only a statistically averaged situation, a disorder in the PtCO interactions being apparent from the orientations of the thermal ellipsoids of the C and O atoms.     

Synthesis and Optoelectronic Properties of a Pt(II) Complex with 2-Pyridin-2-Yl-1,3-Thiazole-4-Carboxylic Acid

A carboxyl functionalized Pt(II) complex PtC₉H₆N₂O₂SC_l2 (I) has been synthesized by the coordination reaction of K₂PtCl₄ with 2-pyridin-2-yl-1,3-thiazole-4-carboxylic acid. The absorption property and photosensitizing performance of I has been studied. Through assembling the dye-sensitized solar cells (DSSCs) based on complex I, a weak solar-energy-to-electricity conversion is presented. Additionally, when complex I was solved in DMF solution, a novel complex PtC9H7N2O3SCl (II) could be obtained. The structure of II has been confirmed by the single-crystal X-ray diffraction (CIF file CCDC no. 1538911).     

Theoretical studies on the reactions CH3SCH3 with OH,CF3, and CH3 radicals

The multiple‐channel reactions OH + CH₃SCH₃ → products, CF₃ + CH₃SCH₃ → products, and CH₃ + CH₃SCH₃ → products are investigated by direct dynamics method. The optimized geometries, frequencies, and minimum energy path are all obtained at the MP2/6‐31+G(d,p) level, and energetic information is further refined by the MC‐QCISD (single‐point) method. The rate constants for eight reaction channels are calculated by the improved canonical variational transition state theory with small‐curvature tunneling contribution over the temperature range 200–3000 K. The total rate constants are in good agreement with the available experimental data and the three‐parameter expressions k₁ = 4.73 × 10^?16T^1.89 exp(?662.45/T), k₂ = 1.02 × 10^?32T^6.04 exp(933.36/T), k₃ = 3.98 × 10^?35T^6.60 exp(660.58/T) (in unit of cm³ molecule^?1 s^?1) over the temperature range of 200–3000 K are given. Our calculations indicate that hydrogen abstraction channels are the major channels and the others are minor channels over the whole temperature range. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Non-collinear magnetic structures of TbCoO3 and DyCoO3

The orthoperovskites TbCoO₃ and DyCoO₃ with Co³⁺ in a non-magnetic low-spin state have been investigated by neutron diffraction down to 0.25 K. Magnetic ordering is evidenced below T_N = 3.3 K and 3.6 K, respectively, and the ordered arrangements are of canted type, A_xG_y for TbCoO₃ and G_xA_y for DyCoO₃ in Bertaut's notation. The experiments are confronted with the first-principle calculations of the crystal field and magnetism of Tb³⁺ and Dy³⁺ ions, located in the Pbnm structure on sites of C_s point symmetry. Both these ions exhibit an Ising behavior, which originates in the lowest energy levels, in particular in accidental doublet of non-Kramers Tb³⁺ (4f⁸ configuration) and in ground Kramers doublet of Dy³⁺ (4f⁹) and it is the actual reason for the non-collinear AFM structures. Very good agreement between the experiment and theory is found. For comparison, calculations of the crystal field and magnetism for other systems with Kramers ions, NdCoO₃ and SmCoO₃, are also included.     

Photoexcitation of CH3NCO,CH3NCS and CH3SCN in the vacuum ultraviolet: Rydberg states and photofragment emission

Photoabsorption cross sections and fluorescence excitation spectra of CH₃NCO, CH₃NCS and CH₃SCN vapor were measured in the vacuum ultraviolet using synchrotron radiation. Many sharp structures observed from CH₃NCO and CH₃SCN in the 120–180 nm region are classified into three Rydberg series and their vibrational progressions, whereas for CH₃NCS six broad bands exhibit no fine structure. The emission which starts to appear at 172.8 ± 1.0 nm excitation of CH₃NCO is attributed to the NCO(A²Σ⁺-X²Π) band. The emissions from CH₃NCS and CH₃SCN are assigned to the A²Π-X²Π and B²Σ⁺-X²Π bands of NCS; the CN(B²Σ⁺-X²Σ⁺) band is also observed at 125 nm excitation of CH₃SCN. The photodissociation processes are discussed in accord with the emission observed.