Determination of vibrational parameters of methanol from matrix-isolation infrared spectroscopy and ab initio calculations. Part 2 – Theoretical treatment including a perturbative approach of the resonances within the methyl group

Ab initio calculations of the potential energy surface of methanol have been developed for the determination of vibrational parameters and their comparison with vibrational data reported in the first part of this work. The strong resonances between the methyl bending and stretching modes, giving rise to polyads of levels P_n in the ranges 3000–2800 (P₂), 4500–4250 (P₃) and 6000–5600 cm⁻¹ (P₄), have been treated by solving for each polyad two Hamiltonian matrices containing off-diagonal terms including both Fermi and Darling-Dennison anharmonic contributions. These terms were calculated from the ab initio determination of the potential energy surface developed up to the quartic terms using the Möller–Plesset 2 method. The choice of the basis set was made to minimize the problem of divergence of the Darling-Dennison constants. Their determination requires however the omission of the terms in which the difference between the harmonic frequencies of the symmetrical methyl stretching and the sum of the two A′ bendings (ω₃–ω₄–ω₅) appears in the denominator. Then, by adjustment of the diagonal elements of the Hamiltonian matrices, it becomes possible to propose a realistic assignment of the matrix spectra.     

The internal energy of product ions formed in mass spectral reactions

Major factors which determine the distribution of internal energy of a primary product ion A⁺, P(E)_A+, at formation are delineated in terms of the quasi-equilibrium theory and a variety of experimental evidence is offered to support these conclusions. These major factors include: the P(E) of the molecular ion, the rate constants as a function of energy, κ(E), for M⁺·→A⁺ + N⁰ and for competing reactions of M⁺·, and the partitioning of excess internal energy between A⁺ and N⁰. The ‘fluctuation effect’ on this partitioning makes P(E)_A+ relatively insensitive to many structural and energy changes.     

The induced circular dichroism of helically shaped racemic bilatrienes

Summary The imperfect mirror image relationship of the circular dichroism of (M) and (P) helical biliverdins bound to a homochiral entity (ICD) has been studied using the kinetically stable racemates (M+P)2 and (M+P)3. The phenomena associated with and eventual implications for the interpretation of ICD spectra of naturally occurring kinetically labile biliverdins in terms of chiral recognition are discussed.Dedicated to ProfessorKarl Schlögl on the occasion of his 70^th birthday     

INTERMEDIATES IN THE PHOTOCONVERSION OF FUNCTIONAL PHYTOCHROME IN FERN SPORES OF Dryopteris–II. In vivo KINETICS OF THE DECAY OF Ii700 AND OF THE FORMATION OF Pfr STUDIED WITH A DOUBLE-LASER APPARATUS*

Abstract— Photoconversion of the red-light-absorbing form of phytochrome, P_r, to the far-red-light-absorbing form, P_fr, was investigated in vivo at 22°C with 600 or 800 ns laser pulses of high spectral purity and induction of spore germination in Dryopteris paleacea was used as indicator for the progress of photoconversion. This reaction is initiated by a saturating R-laser pulse of 648.5 nm, establishing an equilibrium of the photochromic system between P_r and the very early intermediates, Iⁱ₇₀₀ (P_rφ Iⁱ₇₀₀)- The decay of Iⁱ₇₀₀ as well as the formation of P_fr was recorded by the application of a second pulse varied between 698 and 717.5 nm, which inhibits the formation of P_lr being absorbed predominantly by Iⁱ₇₀₀or P_fr, respectively. The most effective inhibition for the second pulse is found up to 10 u.s after the first pulse and this is interpreted by photoreversion of Iⁱ₇₀₀ to P_r; thus reducing the formation of P_fr from Iⁱ₇₀₀. This early inhibition decreases between 10 μs to 100 ms after the R-laser pulse, as a result of the decay of Iⁱ_bl to a bleached species I,;. This decay can be described by three first order kinetics with the rate constants k₁₂= 16830 ± 2970 s^-1, k₁₂= 666 ± 218 s^-1,k₁₃= 9.8 ± 0.9 s^-1. A second inhibition, due to the formation of P_fr, is found for dark intervals <100 ms and can be described by two first order kinetics with the rate constants k₂₁= 2.9 ± 0.6 s^-1 and k₂₂= 0.17 s^-l.     

Multireference configuration interaction study on spectroscopic parameters and molecular constants of PO and PO+

The highly accurate valence internally contracted multireference configuration interaction (MRCI) approach has been employed to investigate the potential energy curves (PECs) for the X²Π, b⁴Σ^?, C²Σ^? states of PO and the X¹Σ⁺ state of PO⁺. For these electronic states, the spectroscopic parameters of the isotopes (P¹⁶O, P¹⁸O, P¹⁶O⁺, and P¹⁸O⁺) have been determined and compared with those of the investigations reported in the literature. The comparison shows that excellent agreement exists between the present results and the available experiments. With the PECs determined here, the first 30 vibrational states for P¹⁶O(X²Π, b⁴Σ^?), P¹⁸O(X²Π, b⁴Σ^?), P¹⁶O⁺(X¹Σ⁺), and P¹⁸O⁺(X¹Σ⁺) are computed when the rotational quantum number J equals zero (J = 0). The vibrational level G(υ), inertial rotation constant B_υ and centrifugal distortion constant D_υ are determined when J = 0. All the results of vibrational states except for P¹⁶O (X²Π) are reported for the first time. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

The collisional quenching of electronically excited arsenic atoms As(42DJ) and As(42PJ), studied by time-resolved attenuation of atomic resonance radiation

A kinetic investigation of electronically excited arsenic atoms in the low-lying states, As(4p^{3 2}D_J) and As(4p^{3 2}P_J), ca. 1.33 and 2.28 eV, respectively, above the 4⁴S_3/2 ground state, has been carried out by atomic absorption spectroscopy. Atoms in these optically metastable states were generated by the pulsed irradiation of suitable arsenic compounds (AsMe₃ for ²D and AsCl₃ for ²P) in different spectral regions and monitored photoelectrically by time-resolved attenuation of atomic resonance radiation. Rate constants for the deactivation of these two states are reported for a range of collision partners. The data are compared with those of the analogous states of lighter atoms in group V, namely, P(3²D_J, 3²P_J) and N(2²D_J, 2²P_J), and discussed in terms of spin and orbital symmetry considerations.     

13C nuclear magnetic resonance of organophosphorus compounds XI—aminophosphines

Natural abundance ¹³C NMR studies have been carried out on a series of organophosphorus compounds possessing P? N bonds. For the first time a one-bond temperature-dependent ¹³C—³¹P nuclear spin coupling was observed for the P-phenyl carbons in bis(N,N-dibenzylamino)phenylphosphine (0-9 Hz) and bis(N,N-diethylamino)phenylphosphine (0–2 Hz). This temperature-dependent behavior can be rationalized in terms of free rotation about the phenyl phosphorus bond with concomitant hindered rotation about the P? N bonds. A conformational preference for the nitrogen and phosphorus lone pairs to exist in the trans orientation is indicated. In the similarly substituted 5-membered heterocyclic ring compound, 1,3-dimethyl-2-phenyl-1,3-diazaphospholidine, the phenyl one-bond coupling increases to (?) 42.1 Hz and becomes temperature independent. These data suggest that ¹J(PC) is very responsive to electronic effects.     

Phosphorus macrocycles and cryptands

The reviews covers authors" studies dealing with the synthesis of P^III- and P^V-containing macrocycles and cryptands. The separation, structural characterization, and the chemical properties of a number of homeomorphic compounds with in,out bridgehead phosphorus atoms are described. Modification of the in-positions in macrobicyclic compounds with bulky groups is described for the first time.     

Analysis of the equations of state of polyolefin melts in terms of the simha-somcynsky hole theory

Pressure–volume–temperature data on melts of low-density polyethylene, polypropylene (PP), poly(butene-1) (PBT), and poly(4-methylpentene-1) (PMP) previously reported by us have been evaluated in terms of the Simha–Somcynsky hole theory of polymeric liquids by a determination of the reducing parameters P^*, V^*, and T^* for each system. Literature data on the reducing parameters of linear polyethylene and of a branched polyethylene of intermediate density are also considered. Agreement with theory is best for the polyethylenes and deteriorates markedly in the series PBT:PP:PMP. These higher polyolefins have very low values of P^*, thus suggesting a deficiency of the Simha–Somcynsky theory at high reduced pressures P? = P/P^*. In these polyolefins, systematic variations of the reducing parameters (and molecular parameters derived therefrom) are noted and discussed. Correlations found previously between T^* and the moleculer weight M₀ of the effective segment of the theory or its hard-core volume M₀V^* are obeyed by the polyethylenes only. The higher polyolefins show serious deviations from these correlations.     

Reaktionshemmender Einflu? von Schwefel auf die Aufkohlung von Nickel in Methan-Wasserstoff-Gemischen

Summary The carburization of nickel in CH₄-H₂ and CH₄-H₂S-H₂ gas mixtures was studied in a flow apparatus at 1060–1280 K applying the resistance-relaxation technique. The reaction of nickel with CH₄ is found to be thermally activated with an activation energy of 128 kJ/mol. The ratecontrolling step is the separation of the first hydrogen atom from the CH₄-molecules impinging on the surface. Small H₂S-amounts, resulting in PH₂S/PH₂-ratios between 8 × 10^–9 and 9 × 10^–5 decrease the initial carburization rate by a factor of up to 100. The kinetic data are interpreted in terms of poisoning of active surface sites by adsorbed sulfur. From this analysis adsorption isotherms for sulfur are derived.     

Calculation of the 4S?4P0 spectrum of lithiumlike ions by the Hylleraas method

The energies of the five lowest ⁴S and ⁴P⁰ states for three-electron ions for 3?Z?10 have been calculated by the Hylleraas method. The largest basis set used contained 97 terms with odd as well as even powers of r_ij. The change of scale r′ = Zr was applied to the Hamiltonian so that the same basis sets could be used for all the three-electron ions leading to great savings in computing time.     

Synthesis,Structure, and Energetic Properties of 1,5‐Diaminotetrazolium Sulfate Salts

1,5‐diaminotetrazolium chloride (DATC) and 1,5‐diaminotetrazolium sulfate (DATS) were synthesized in this work. The structures of DATS and DATC were characterized. The single crystal of DATS was first cultured, and its structure was analyzed. The thermal behavior of DATS was investigated. The activation energy and pro‐exponential factor were calculated, E_k = 120.86 KJ/mol, A_k = 10^12.96 s^?1. The density, heat of formation, detonation pressure, and detonation velocity of DATS were first calculated. The detonation pressure and detonation velocity of DATS are P = 11.877 GPa, D = 5.617 km s^?1, which are smaller than those of 1,5‐diaminotetrazolium nitrate (DATN) (P = 33.3GPa, D = 8.77 km s^?1).     

Pressure Effects in the Solvolysis of Benzyl Chlorides

Rates of solvolysis of benzyl chloride and of substituted benzyl chlorides have been measured in an acetone-water mixture (acetone mole fraction 0.147) at pressures ranging from atmospheric to 1 kbar. Pressure studies have also been made for p-methyl benzyl chloride in various acetone-water mixtures. Measurements have also been made of the partial molar volumes of the reactants. The plots of log k against pressure are fitted to a second-degree polynomial in P, and values of ΔV^? and (δΔV^//δP)_T are obtained. The ΔV^? values are all negative, having values ranging from ?18 to ?24 cc/mole. The results are interpreted on the view that the mechanisms are S_N2(1), i.e. are towards the S_N1 end of the S_N2 spectrum of behavior. The ΔV^? values steadily become more negative in the series p? CH₃, H, p? Cl, pNO₂, and this is interpreted in terms of the greater spreading of positive charge in the p? CH₃ case and in terms of greater S_N2(2) character in the p? NO₂ case. The ΔV^? values go through a minimum as the solvent composition is varied, a result that is related to the existence of a corresponding maximum in the partial molar volumes of the reactant. The (δΔV^?/δP)_T values show a negative correlation with ΔV^?, suggesting, as expected, that the more compact activated complexes are the least compressible.     

Maximum-entropy analysis of atomic compton profiles

The maximum-entropy formalism is used to obtain approximations to the atomic Compton profile, ??(q), in terms of the first few radial expectation values 〈Pⁿ〉 of the momentum density γ(p). This method leads to the least-biased results by the information not used. In particular, analytical and numerical approximations to the kinetic energy T and to the height of the peak ??(O) and the half-width q_0.5 of the Compton profile are obtained. Our results generalize and improve some approximations to ??(q) previously obtained by other authors. For illustration, the accuracy of these approximations are studied by means of near-Hartree–Fock wave functions. © 1995 John Wiley & Sons, Inc.     

Alcoylation d'acridanone-9. Premiers exemples de O-alcoylation dans cette série de composés

The results of nucleophilic substitution of the 2-methoxy-9-acridone are discussed in terms of competition between both ionic sites N^? and O^?, of the molecule. They are the first examples of O-alkylation of substituted 9-acridone.     

La(Ni2/3Nb1/3)O3 by neutron powder diffraction

Lanthanum nickel niobium trioxide has been synthesized and its structure refined for the first time. It was found to be a member of the family of technologically important `double perovskites', crystallizing in the monoclinic space group P2₁/n. The structure is characterized by a strong orthorhombic pseudosymmetry and a concurrent exhibition of both 1:1 B‐cation ordering and a⁻a⁻c⁺‐type tilting of the (Ni/Nb)O₆ structural units. Trivalent lanthanum resides on the perovskite A site, which is strongly distorted owing to the tilting of the (Ni/Nb)O₆ sublattice. Ordering of divalent nickel and pentavalent niobium on the B sublattice is described in terms of two twofold special positions (2c and 2d), with nickel taking almost complete occupancy of the 2d site and the 2c position being occupied by a statistical distribution of nickel and niobium.     

Organic Nanoprobes for Fluorescence and 19F Magnetic Resonance Dual‐Modality Imaging

Multimodal imaging techniques have been demonstrated to be greatly advantageous in achieving accurate diagnosis and gained increasing attention in recent decades. Herein, we present a new strategy to integrate the complementary modalities of ¹⁹F magnetic resonance imaging (¹⁹F MRI) and fluorescence imaging (FI) into a polymer nanoprobe composed of hydrophobic fluorescent organic core and hydrophilic fluorinated polymer shell. The alkyne‐terminated fluorinated copolymer (Pn) of 2,2,2‐trifluoroethyl acrylate (TFEA) and poly(ethylene glycol) methyl ether acrylate (PEGA) was first prepared via atom transfer radical polymerization (ATRP). The PEGA plays an important role in both improving ¹⁹F signal and modulating the hydrophilicity of Pn. The alkynyl tail in Pn is readily conjugated with azide modified tetra‐phenylethylene (TPE) through click chemistry to form azo polymer (TPE‐azo‐Pn). The core‐shell nanoprobes (TPE‐P3N) with an average particle size of 57.2 ± 8.8 nm are obtained via self‐assembly with ultrasonication in aqueous solution. These nanoprobes demonstrate high water stability, good biocompatibility, strong fluorescence and good ¹⁹F MRI performance, which present great potentials for simultaneous fluorescence imaging and ¹⁹F–MR imaging.     

Sulfur‐Rich Phosphorus Sulfide Molecules for Use in Rechargeable Lithium Batteries

A new family of sulfur‐rich phosphorus sulfide molecules (P₄S_10+n ) and their electrochemical reaction mechanism with metallic Li has been explored. These P₄S_10+n molecules are synthesized by the reaction between P₄S₁₀ and S. For Li batteries, the P₄S₄₀ molecule in the series of P₄S_10+n molecules provides the highest capacity, which has a first discharge capacity of 1223 mAh g⁻¹ at 100 mA g⁻¹ and stabilizes at approximately 720 mAh g⁻¹ at 500 mA g⁻¹ after 100 cycles. This new class of sulfur‐rich P₄S_10+n molecules and its electrochemical behavior for room‐temperature Li⁺ storage could provide novel insights for phosphorus sulfide molecules and high‐energy batteries.     

Structural Patterns and Dimensionality in Magnesium Borophosphates: The Crystal Structures of Mg2(H2O)[BP3O9(OH)4] and Mg(H2O)2[B2P2O8(OH)2]·H2O

Hydrothermal investigations in the system MgO/B₂O₃/P₂O₅(/H₂O) yielded two new magnesium borophosphates, Mg₂(H₂O)[BP₃O₉(OH)₄] and Mg(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O. The crystal structures were solved by means of single crystal X‐ray diffraction. While the acentric crystal structure of Mg₂(H₂O)[BP₃O₉(OH)₄] (orthorhombic, P2₁2₁2₁ (No. 19), a = 709.44(5) pm, b = 859.70(4) pm, c = 1635.1(1) pm, V = 997.3(3) × 10⁶ pm³, Z = 4) contains 1D infinite chains of magnesium coordination octahedra interconnected by a borophosphate tetramer, Mg(H₂O)₂[B₂P₂O₈(OH)₂]·H₂O (monoclinic, P2₁/c (No. 14), a = 776.04(5) pm, b = 1464.26(9) pm, c = 824.10(4) pm, β = 90.25(1)°, V = 936.44(9) × 10⁶ pm³,Z = 4) represents the first layered borophosphate with 6³ net topology. The structures are discussed and classified in terms of structural systematics.