Exciton states in organic alloys: Naphthalene-perdeuteronaphthalene

The lower band-edge energy of the first single exciton of naphthalene has been determined as a function of concentration in a C₁₀H₈/C₁₀D₈ alloy. Experimentally, the vibronic 0–512 fluorescence at 2 K and 1 cm^?1 resolution has been measured. Theoretically, the coherent potential approximation (CPA) and the negative factor counting (NFC) results have been derived from the work of Hong and Kopelman. Agreement is good within the experimental and computational uncertainties (2–3 cm^?1).     

Interpretation of experimental Mössbauer quadrupole splittings of iron pentacyanide complexes using molecular orbital theory

Semiempirical self-consistent-field molecular-orbital calculations are carried out for six iron-pentacyanide complexes and are used to interpret their experimental Mössbauer quadrupole splittings. Probable orientations are identified for the C₆H ₅ ^? and NO ₂ ^? groups in Fe(CN)₅NOC₆H ₅ ^?3 and Fe(CN)₅NO ₂ ^?4 . Calculations on Fe(CN)₅NO^?2 and Fe(CN)₅NO^?3 can simultaneously be brought into agreement with experiment by reparametrization to make the NO group more positively charged. All the calculations indicate the importance of including all the Fe 3d and 4p orbitals in the calculations and of considering neighboring-atom effects.     

Quantitative tests of mixed crystal excition theory. I. Naphthalene monomer1B2u and 3B1u spectra

A quantitative, computer processed spectroscopic study, using photon counting, on the first excited triplet and singlet states of dilute isotopic mixed crystals of naphthalene at 2 K is presented for C₁₀H₈; 1-DC₁₀H₇; 2-DC₁₀H₇; 1,4-D₂C₁₀H₆; 1,4,5-D₃C₁₀H₅; 1,4,5,8-D₄C₁₀H₄; 1,2,4,5,8-D₅C₁₀H₃; a β-D₄C₁₀H₄ and a β₂-D₆C₁₀H₂ as guests in C₁₀D₈ host crystals (and, for comparison, also for the same guests in a durene host crystal). The guest—host relative polarization Rashba formula has been verified quantitatively, and, as an added bonus, the elusive polarization ratio of the pure naphthalene crystal singlet Davydov components has been found to be 80 ± 20 (b/a), which is in poor agreement with the transition octupole—transition octupole model. The experimental guest energies and their concomitant quasiresonance shifts for bound singlet states (as well as the occurrences of unbound states) are in excellent quantitative agreement (about 1 cm^?1) with those calculated using a Green's function formalism based on the ideal mixed crystal approximation and on a restricted Frenkel type dispersion relation derived from resonance pairs. The same Green's function also accounts quantitatively (within 10%) for the guest singlet state exciton localizations (guest excitation amplitudes). The triplet exciton state reveals an orientational site splitting (about 0.7 cm^?1) for the 0—0 transition of the I-DC₁₀H₇ guest in C₁₀D₈ host. The order of the α and β substituted deuteronaphthalenes in the triplet state is reversed from that of the singlet state. The last two observations are related to the different nature of the lowest Π-Π^* singlet and triplet states of naphthalene.     

Neue Alkylchlorsulfonium-Salze und Kristallstruktur von Diethylchlorsulfoni-umhexachloroantimonat (C2H5)2SCl+SbCl6−

New Alkylchlorosulfonium Salts and Crystal Structure of Diethylchlorosulfonium-Hexachloroantimonate (C₂H₅)₂SCl⁺SbCl₆^? We describe the preparation and spectroscopic characterization of Dialkylchlorosulfonium-Hexachloroantimonates R₂SCl⁺SbCl₆^? (R = C₂H₅, i-C₃H₇) and the crystal structure of Diethylchlorosulfonium-Hexachloroantimonate (C₂H₅)₂SCl⁺SbCl₆^? at 172(1) K. The salt crystallize in the orthorhombic space group P2₁2₁2₁ with a = 980.4(13) pm, b = 1010.6(8) pm, c = 1492.8(14) pm with four formula units per unit cell.     

Interactions of antimony(III) halides with amides and tetramethylurea in 1,2-dichloroethane solution

The interactions of SbCl₃, SbBr₃ and SbI₃ with N,N-dimethylformamide (DMF); N,N-dimethylacetamide (DMA) and tetramethylurea (TMU) have been studied in 1,2-dichloroethane solution. The equilibrium constants and the respective variations of enthalpy for 1:1 and 1:2 species were obtained by means of the incremental calorimetric titration technique. From ΔH₁^θ values, the acidity order SbCl₃ > SbBr₃ > SbI₃ and the basicity order TMU > DMA > DMF were established. The ionization in solution such as autocomplex formation and halides displacement are discussed using conductometric titration values.     

Kinetic studies of the reaction of C2H5 with O2 at 295 K

The reaction between C₂H₅ and O₂ at 295 K has been studied with a flow reactor sampled by a mass spectrometer. With helium as the carrier gas the rate coefficient was found to increase from (1.2 ± 0.3) × 10^?12 to (3.6 ± 0.9) × 10^?12 cm³/s as [He] was increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm^?3. The importance of has been determined from a knowledge of the initial C₂H₅ concentration together with a measurement of the C₂H₄ produced in reaction (5). F, the fraction of the C₂H₅ radicals removed by path (5), was found to decrease from 0.15 to 0.06 as [He] increased from 2 × 10¹⁶ to 3.4 × 10¹⁷ cm^?3. The rate coefficient for reaction (5) was found to be independent of [He] and to have a value of (2.1 ± 0.5) × 10^?13 cm³/s. The variation in F reflects the fact that k_1b increases as [He] increases. These observations are taken as evidence for a direct mechanism for C₂H₄ production and a collision-stabilized route for C₂H₅O₂ formation. Calculations indicate that the high-pressure limit for reaction (1b) is ～4.4 × 10^?12 cm³/s and that in the polluted troposphere the branching ratio for reactions (1b) and (5) will be ～l20.     

Die Kristallstruktur des 1 : 1-Adduktes zwischen Antimontrichlorid und Diphenylammoniumchlorid,SbCl3 · (C6H5)2NH2+Cl−

The Crystal Structure of the 1:1 Addition Compound between Antimony Trichloride and Diphenylammonium Chloride, SbCl₃ · (C₆H₅)₂NH₂⁺Cl^? The 1:1 addition compound between antimony trichloride and diphenylammoniumchloride SbCl₃ · (C₆H₅)₂NH₂⁺Cl^? crystallizes in the monoclinic space group P2₁/n with a = 5.668(8), b = 20.480(12), c = 14.448(17) Å, β = 110.4(1)° and Z = 4 formula units. Chains of SbCl₃ molecules and anion cation chains are bridged by Cl ions and form square tubes. The coordination of the Sb atoms by Cl atoms by Cl atoms and Cl ions is distorted octahedral. Mean distances are Sb? Cl = 2.37 Å for Sb? Cl (3×), 3.09 Å for Sb…Cl^? (2×) and 3.42 Å for Sb…Cl (1×). The Sb…Cl^? contacts and hydrogen bonds NH…Cl^? at 3.15 Å generate tetrahedral coordination of the Cl ions.     

Luminescence of antimony(III) halide complexes with aniline

The antimony(III) chloride and bromide complexes with aniline, (C₆H₅NH₃)₂SbCl₅·(C₆H₅NH₃)Cl·H₂O (I) and (C₆H₅NH₃)₂SbBr₅ (II), were synthesized, and their spectral luminescence properties were studied. An interesting peculiarity of I and II is the possibility of selective excitation of luminescence in the π system of the (C₆H₅NH₃)⁺ outer sphere anilinium cation and intrinsic luminescence of the s ² ion. The population scheme for the luminescent antimony ³ P ₁ level in I and II is discussed using the luminescence, UV, and photoelectron spectroscopy data. Original Russian Text ? T.V. Sedakova, A.G. Mirochnik, V.E. Karasev, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 2, pp. 380–382.     

Raman spectroscopic investigation of interactions in a naphthalene: Octafluoronaphthalene crystalline complex

The nature of interactions between naphthalene and octafluoronaphthalene in the C₁₀H₈:C₁₀F₈ crystalline complex is studied by Raman spectroscopy. Phonon bands are examined within the framework of our previously proposed sublattice and giant molecule models to derive information regarding the strength of the interactions. To investigate the specific nature of these interactions, a comparative study is made of the internal vibrations observed in the C₁₀H₈:C₁₀F₈ complex with those found in pure one component crystals. The result obtained indicates that although naphthalene and octafluoronaphthalene weakly interact, specific electrostatic polarization interactions do exist in the C₁₀H₈:C₁₀F₈ crystalline complex.     

Aromaten-Komplexe mit Halbsandwich-Struktur: Die 1:1-Komplexe des Mesitylens mit SbCl3, SbBr3, BiCl3 und BiBr3

Arene Complexes with a Half-Sandwich Structure: The 1:1 Complexes of Mesitylene with SbCl₃, SbBr₃, BiCl₃, and BiBr₃ 1,3,5-Trimethylbenzene forms stable 1:1 complexes with SbCl₃, SbBr₃, BiCl₃, and BiBr₃ of the stoichiometry C₆H₃Me₃·EX₃ ( 1 – 4 ). According to the results of X-ray structure analyses of compounds 2 and 3 , one arene molecule is coordinated to each antimony or bismuth atom characterizing these adducts as half-sandwich species. To a good approximation the mesitylene molecules are centered over the metal atoms, but deviations from strict η⁶-hapticity are larger for antimony than for bismuth. – Despite some obvious analogies in many features of the structures, 2 and 3 are not isostructural. Differences appear with regard to the halogen bridging between the EX₃ moieties giving rise to the formation of two-dimensional networks (EX₃)_n covered above and below by mesitylene molecules. The structural and sequential principles of the layers differ in a characteristic way for 2 and 3 .     

Über die Reaktion von HCl im System HF/SbF5 und die Kristallstruktur von SbCl3F2

On the Reaction of HCl with HF/SbF₅ and the Crystal Structure of SbCl₃F₂ The reaction of HCl in HF/SbF₅ solution at ?78°C yields H₂F⁺SbClF₅^?. At ?40°C formation of SbCl₃F₂ was observed, which crystallizes in the tetragonal space group I-4 with a = 1 281.6(5) pm, c = 758.1(6) pm with 8 formula units per unit cell. The structure contains cis-fluorine-bridged tetramers, in which Sb has a distorted octahedral coordination.     

Synthese,Kristallstrukturen und 121Sb-Mößbauer-Spektren von [SbBr3(15-Krone-5)], [SbBr2Me(15-Krone-5)] und [SbBr2Ph(15-Krone-5)]

Synthesis, Crystal Structure, and ¹²¹Sb-Mössbauer Spectra of [SbBr₃(15-Crown-5)], [SbBr₂Me(15-Crown-5)], and [SbBr₂Ph(15-Crown-5)] The compounds [SbBr₃(15-crown-5)] ( 1 ), [SbBr₂Me(15-crown-5)] ( 2 ), [SbBr₂Ph(15-crown-5)] ( 3 ), and [SbCl₂Me(15-crown-5)] ( 4 ) are formed by the reaction of 15-crown-5 with SbBr₃, SbBr₂Me, SbBr₂Ph, and SbCl₂Me, respectively, in toluene solution at ?40°C. The complexes were characterized by IR spectroscopy, ¹²¹Sb-Mössbauer spectroscopy, 1–3 as well as by X-ray structure determinations.

• 1 : Space group P2₁2₁2₁, Z = 4, 1735 observed, independent reflections, R = 0.050, Lattice dimensions at ?65°C: a = 787.03(7); b = 1313.0(2); c = 1619.3(2) pm.
• 2 : Space group Pca2₁, Z = 8, 2730 observed, independent reflections, R = 0.050, Lattice dimensions at ?65°C: a = 1308.2(2); b = 1611.8(2); c = 1640.5(3) pm.
• 3 : Space group P2₁/n, Z = 4,2458 observed, independent reflections, R = 0.040, Lattice dimensions at ?60°C: a = 900.3(3); b = 1390.6(6); c = 1618.5(7) pm, β = 96.32(3)°.

The complexes 1–3 have molecular structures, in which the antimony atoms are surrounded by the five oxygen atoms of the crown ether molecule and by three ligands Br₃, Br₂CH₃, Br₂Ph, respectively.     

Naphthalene complexes: V. Arene exchange reactions in naphthalenechromium complexes

Di-η⁶-naphthalenechromium(0) (1) reacts at 150°C with benzene to yield (η⁶-naphthalene)(η⁶-benzene)chromium(0) (3) in 76% yield. In the presence of THF, 1 undergoes Lewis base catalyzed arene exchange at 80°C. Reactions of 1 with substituted arenes yield the mixed sandwich complexes 4 and 6–10 (arene = 1,4-C₆H₄Me₂, 1,3,5-C₆H₃Me₃, C₆Me₆, 1,4-C₆H₄(OMe)₂, 1,4-C₆H₄F₂ and 1,4-C₁₀H₆Me₂). In all but one case (with 1,4-dimethylnaphthalene) exchange of a single naphthalene ligand is observed. In marked contrast to the lability of 1, dimesitylenechromium(0) (5) is inert to arene displacement in benzene up to 240°C. The molecular structure of 3 has been determined by X-ray crystallography. The crystal data are as follows: a 7.784(1), b 13.411(2), c 22.772(5) Å, Z = 8, space group Pbca. The structure was refined to a R_w value of 0.043. The naphthalene ligand in 3 is nearly planar and parallel to the approximately eclipsed benzene ring. Metal atom-ring distances are 1.631(9) and 1.611(4) Å for naphthalene and benzene, respectively. Catalyzed and uncatalyzed naphthalene exchanges in the sandwich complex are compared to the analogous reactions with the Cr(CO)₃ complex 2. Naphthalene exchange in 2 in benzene is 10³ to 10⁴ times faster than arene exchange in other arenetricarbonylchromium compounds. The mild conditions for Lewis base catalyzed naphthalene exchange make 2 a good precursor of other arenetricarbonylchromium compounds. Examples include the Cr(CO)₃ complexes of styrene, benzocyclobutene, 1-ethoxybenzocyclobutene, 1,8-dimethoxy-9,10-dihydroanthracene and 1,4-dimethylnaphthalene.     

Relativistic molecular orbital theory of zero-field splittings in triplets

A method of calculating matrix elements of 1/r₁₂ in a basis of Dirac scattered-wave (DSW) orbitals is outlined. In the limit c → ∞, this method reduces to that described by Cook and Karplus for non-relativistic orbitals. For triplet states that can be described by a single configuration with two unpaired electrons, the relativistic exchange integrals give not only the singlet—triplet splittings (as in non-relativistic theory), but also the spin—orbit contributions to the triplet zero-field splittings. Results are reported for the ³ (n → π*) excited state of γ-thiopyrone (4H-pyran-4-thione), which has a very large value of D (calc. ?31 cm^?1, exp. ?24 to ?28 cm^?1).     

Kinetic study of reactions of C2H5O2 with NO at 298 K and 0.55 – 2 torr

The kinetics of C₂H₅O₂ and C₂H₅O₂ radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis. The temporal profiles of C₂H₅O were monitored by LIF. The rate constant for C₂H₅O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k₂ = (1.25±0.04) × 10^?11, (1.66±0.06) × 10^?11, (1.81±0.06) × 10^?11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm³ molecule^?1 s^?1). The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C₂H₅O + NO + M → C₂H₅ONO + M (2a), C₂H₅O + NO → CH₃CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k_2a and for k_2b : k = (2.6±1.0) × 10^?28 cm⁶ molecule^?2 s^?1, k = (3.1±0.8) × 10^?11 cm³ molecule^?1 s^?1 and k_2b ca. 8 × 10^?12 cm³ molecule^?1 s^?1. The present value of k, obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10^?27 cm⁶ molecule^?2 s^?1 recommended in air. The rate constant for the reaction C₂H₅O₂ + NO → C₂H₅O + NO₂ (3) has been measured at 1 torr of He from the simulation of experimental C₂H₅O profiles. The value obtained for k₃ = (8.2±1.6) × 10^?12 cm³ molecule^?1 s^?1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc.     

Zeeman experiments on the 3Eu α 1A1g transition of platinum porphein in an n-alkane single crystal at 4.2

We report absorption spectra from the ground state to the photoexcited triplet state of platinum porphin (PtP) in single crystals of n-octane (C₈) and n-decane (C₁₀) at 4.2 K, with and without a magnetic field. For PtP in C₁₀ the same transition was studied in emission. From the experiments, values are derived of the spin-orbit coupling parameter Z, the crystal field splitting δ and the orbital angular momentum A for PtP in the two hosts: Z = 76 ± 2 cm^?1 (C₈, C₁₀), δ = 71 ± 1 cm^?1 (C₈), 55 ± 1 cm^?1 (C₁₀) and A = 1.6 ± 0.1 (C₈, C₁₀). For the ratio of the in-plane and the z-polarized electric dipole transition moments we obtain ¦Mx,y¦/¦Mz¦=76± 0.3 (C₈).     

Crystal structure and luminescence of antimony(III) bromide with aniline

The atomic structure of antimony(III) bromide crystals with anilinium was determined by X-ray diffraction analysis of (C₆H₅NH₃)₂SbBr₅ (a = 19.704(3) Å, b = 7.914(1) Å, c = 25.556(4) Å; space group Pbca, Z = 8, ρ_calc = 2.365 g/cm³). The crystal structure consists of infinite chains of [SbBr₅]^2? complex anions formed by sharing six vertices and the anilinium (C₆H₅NH₃)⁺ cations, through which the chains are linked in layers by N-H...Br hydrogen bonds. The geometrical aspects that determine the luminescent spectral properties of the complex are discussed.     

Rate constants for the elementary reactions between CN radicals and CH4, C2H6, C2H4, C3H6, and C2H2 in the range: 295 ⩽ T/K ⩽ 700

Pulsed laser photolysis, time-resolved laser-induced fluorescence experiments have been carried out on the reactions of CN radicals with CH₄, C₂H₆, C₂H₄, C₃H₆, and C₂H₂. They have yielded rate constants for these five reactions at temperatures between 295 and 700 K. The data for the reactions with methane and ethane have been combined with other recent results and fitted to modified Arrhenius expressions, k(T) = A′(298) (T/298)ⁿ exp(?θ/T), yielding: for CH₄, A′(298) = 7.0 × 10^?13 cm³ molecule^?1 s^?1, n = 2.3, and θ = ?16 K; and for C₂H₆, A′(298) = 5.6 × 10^?12 cm³ molecule^?1 s^?1, n = 1.8, and θ = ?500 K. The rate constants for the reactions with C₂H₄, C₃H₆, and C₂H₂ all decrease monotonically with temperature and have been fitted to expressions of the form, k(T) = k(298) (T/298)ⁿ with k(298) = 2.5 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.24 for CN + C₂H₄; k(298) = 3.4 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.19 for CN + C₃H₆; and k(298) = 2.9 × 10^?10 cm³ molecule^?1 s^?1, n = ?0.53 for CN + C₂H₂. These reactions almost certainly proceed via addition-elimination yielding an unsaturated cyanide and an H-atom. Our kinetic results for reactions of CN are compared with those for reactions of the same hydrocarbons with other simple free radical species. © John Wiley & Sons, Inc.     

Sulfoximid und Sulfoximidium-Salze – Strukturen und H?Brückenbindungen

Sulfoximide and Sulfoximidium Salts – Structures and Hydrogen Bonding In the solid state dimethylsulfoximide ( 1 ) (orthorhombic; space group Pbca; a = 577.8, b = 931.2 and c = 1645.6 pm) makes intermolecular N? H ? N hydrogen bonds. The hydrogen halide salts (CH₃)₂S(O)NH₂⁺Hal^? (( 2 ), Hal^??Cl^?; ( 4 ), Hal^??Br^?) reacts with metal halides to yield (CH₃)₂S(O)NH₂⁺MHal with the complex anions (( 5 ), MHal?SbCl₄^?; ( 6 ), MHal?SbCl₅^2?; ( 7 ), MHal?SbCl₆^?; ( 8 ), MHal?SbBr₅^2?; ( 9 ), MHal?AlCl₄^?). 2 crystallizes from ethanol (96%) as [(CH₃)₂S(O)NH₂⁺Cl^?]₂ · H₂O ( 3 ). The structures of 3 (monoclinic; space group P2₁/c; a = 917.0, b = 1344.7, c = 1080.8 pm and β = 103.8°; Z = 10), 4 (orthorhombic; space group Pbcn; a = 1028.9, b = 1132.6, c = 1074.1 pm; Z = 8) and 6 (monoclinic; space group C2/c; a = 2041.1, b = 1101.4, c = 3365.6 pm and β = 153.8°; Z = 8) are determined by X-ray analysis. In 6 Sb is coordinated in a distorted octahedra by 6 Cl in three short (mean 245,5 pm; SbCl₃) and three long distances (291 to 299 pm; Cl^?). Two of the chloride ions connect the Sb atoms to infinite Sb …? Cl …? Sb chains. Except for 7 and 9 there are bridges between the NH₂ groups and the halide ions. The NH valence vibrations are discussed in view of hydrogen bonding.     

Rates of reaction of atomic oxygen with C2H3F,C2H3Cl,C2H3Br, 1,1-C2H2F2, and 1,2-C2H2F2

Rate constants for the reactions of atomic oxygen (O³P) with C₂H₃F, C₂H₃Cl, C₂H₃Br, 1,1-C₂H₂F₂, and 1,2-C₂H₂F₂ have been measured at 307°K using a discharge-flow system coupled to a mass spectrometer. The rate constants for these reactions are (in units of 10¹¹ cm³ mole^?1 s^?1) 2.63 ± 0.38, 5.22 ± 0.24, 4.90 ± 0.34, 2.19 ± 0.18, and 2.70 ± 0.34, respectively. For some of these reactions, the product carbonyl halides were identified.