Experimental and theoretical investigations of the nuclear quadrupole resonance of 127I in orthoperiodic acid,H5IO6

Pure nuclear quadrupole resonance of ¹²⁷I in H₅IO₆ has been reported to occur at 44.976 MHz (m = ±$\text{3}\text{2}$?m = ±$\text{1}\text{2}$ transition) and 83.960 MHz (m = ±$\text{5}\text{2}$? m = ±$\text{3}\text{2}$ transition) at 296 K (ref. 1). Using an externally quenched frequency modulated super regenerative spectrometer Zeeman studies have been performed at 296 K on single crystals of H₅IO₆ growm from aqueous solution by observation of the ±$\text{sol3}\text{2}$?±$\text{1}\text{2}$ transition. The zero-splitting locus method has been employed for the determination of the EFG parameters. The data show that there are two physically inequivalent sites, having average asymmetry parameters, η, of 0.25, located in the unit cell. The maximum field gradient is found to lie along the short bond I-O(2) as suggested by Rama Rao and Weiss (ref. 1). The EFG parameters obtained by detailed molecular orbital calculations (CNDO/2 and INDO method) are compared with the experimental results.     

Structure cristalline du composé RbEu3F10

Crystals of RbEu₃F₁₀ are cubic with a = 11.844 Å, Z = 8, and three possible space groups, $\text{Fm3m, F}\text{4}\text{3m}$, and F432. The structure has been resolved from three-dimensional X-ray data and refined by the least-squares method. The final R values are, respectively, 0.065 and 0.067 for Fm3m and $\text{F}\text{4}\text{3m}$, and are not significantly different. The rare earth symmetry is C_4v for Fm3m and C_2v for $\text{F}\text{4}\text{3m}$. Consequently, we have used the Eu³⁺ ion in the RbEu₃F₁₀ phase as a structural probe in order to state precisely the symmetry of the lanthanide site and distinguish among the possible space groups.     

H3N·PF5 and H2NPF5−, new compounds in the system H3N/PF5

Phosphorus pentafluoride was reported long ago to give adducts 2 PF₅ ·5 NH₃ (1) and nNH₃·PF₅ (n= 1 ? 4) (2). None of the compounds was characterised in detail. Repeating the reaction of PF₅ and NH₃ we found the adduct H₃N·PF₅, $\text{1}$, in 8% yield besides (H₂N) ₂PF₃ (3) and NH₄PF₆. However, HF and (F₂P=N)₃ gave $\text{1}$ in 41% yield. The ¹H, ¹⁹F, and ³¹P n.m.r. spectra of $\text{1}$ exhibit ¹⁴NH, ¹⁴NPF(cis), and ¹⁴NP coupling. The x-ray structure determination shows almost perfect octahedral geometry at phosphorus with a PN bond length of 1.842 ā. Compound $\text{1}$ is soluble in water without decomposition. Treatment with NH₃ leads to the anion H₂NPF₅^?. Upon heating $\text{1}$ forms in good yield H₂NPF₄ and NH₄PF₆. Without a solvent $\text{1}$ and NH₃ react to give (H₂N) ₂PF₃. A mechanism for the ammonolysis of PF₅ is proposed.     

Etude structurale du conducteur anionique Bi0,765Sr0,235O1,383

The structure of an O^2? conductor, the rhombohedral (a = 9.75Å, α = 23.49°) low-temperature form of the solid solution $\text{Bi}{}_{\mathrm{1?x}}\text{Sr}{}_{\mathrm{x}}\text{O}{}_{\mathrm{<mtext>1,5?</mtext><mtext>x</mtext><mtext>2</mtext>}}\text{(x = 0.235, Z = 3)}$ has been solved in space group $\text{R}\text{3}\text{m}$ by means of Fourier synthesis and least-squares refinements. Intensity data were corrected for absorption. The final R value is 0.030 for 302 independent planes. Most of the bismuth atoms are located on a first set with a distorted tetrahedral coordination while the remaining bismuth and the strontium atoms are distributed on a single position with an eightfold (6 + 2) oxygen coordination. Two types of anionic sites are detected within the tetrahedral voids of the cation sheets stacked along the [III] axis. This results in a layered structure, with loosely bound oxide ions, providing a basis for the interpretation of the ionic conductivity of the phase.     

Structure cristalline du phosphatoantimonate K3Sb3P2O14

K₃Sb₃P₂O₁₄ crystallizes in the rhombohedral system, space group $\text{R}\text{3}\text{m}$ with a = 7.147(1) Å, c = 30.936(6) Å, Z = 3. The structure was determined from 701 reflections collected on a Nonius CAD4 automatic diffractometer with $\text{Mo}\text{K}\text{α}$ radiation. The final R index and the weighted R_w index are 0.033 and 0.042, respectively. The structure is built up from layers of SbO₆ octahedra and PO₄ tetrahedra sharing corners. The potassium ions are situated between the (Sb₃P₂O₁₄)^3? covalent layers.     

Extraction-polarographic determination of cobalt(II) and nickel(II) as 2,2′-bipyridine complexes in acetonitrile

The tris(2,2′-bipyridine)cobalt(II) complex gives a reversible d.c. wave with E$\text{1}\text{2}$ = ?1.02 V vs. SCE and a sharp differential pulse peak at E_p = ?1.03 V in a salted-out acetonitrile phase. A simple selective method is described for the determination of cobalt(II); down to 0.25 μg of cobalt(II) can be determined in presence of large amounts of Ni, Zn, Cd, Pb, and Cu; iron(III) can be masked with sodium fluoride. The method is applicable to the determination of >0.0l% cobalt in nickel salts and >5 × 10^?5% cobalt in iron salts. Nickel(II) can also be extracted from aqueous solution and determined by differential pulse polarography, even in presence of a 20-fold amount of cobalt(II) by masking with EDTA; >0.01% of nickel in cobalt salts can be determined reproducibly.     

Oxydes de plomb. I. Structure cristalline du minium Pb3O4, à température ambiante (293 K)

The structure of Pb₃O₄ at 293 K has been refined to an R value of 0.06, using 29 neutron diffraction data obtained from a powdered sample.Oxygen atoms are displaced in the quadratic cell (space group $\text{P4}{}_2\text{mbc}\text{; a = 8.811}$ Å and c = 6.563 Å) with respect to previous results obtained by several authors. The interatomic Pb^IVO and Pb^IIO distances are compared with those found in other lead oxides. While the oxygen octahedra around Pb^IV atoms are characterized by bondings a little too long, the divalent lead coordination is characterized by bondings a little too short.     

The optical absorption and emission spectra of Cs2NaSmCl6

Optical absorption and emission spectra are reported for single crystals of the cubic elpasolite Cs₂NaSmCl₆. The variable temperature spectra obtained at high resolution are assigned using energies and relative intensities. Transitions from the ground level, ⁶H_{$\text{5}\text{2}$} to cystal fi levels of ⁶H_{$\text{7}\text{2}$-$\text{15}\text{2}$}, ⁶F_{$\text{1}\text{2}$-$\text{11}\text{2}$}, ⁴G_{$\text{5}\text{2}$-$\text{9}\text{2}$}, ⁴F_{$\text{3}\text{2}$,$\text{5}\text{2}$}, ⁴I_{$\text{9}\text{2}$}, and ⁶P_{$\text{3}\text{2}$, $\text{5}\text{2}$} are located and characterized. Intensity calculations are reported for magnetic dipole allowed transitions. The dominance of vibronic intensity in ⁶H_{$\text{5}\text{2}$}→⁶F _{$\text{1}\text{2}$-$\text{9}\text{2}$} and ⁶P_{$\text{3}\text{2}$, $\text{5}\text{2}$} transitions is accounted for qualitatively through the ligand polarization model involving quadrupole metal (Sm³⁺)-ligand (Cl^?) interaction mechanisms. The E_u″(⁶H_{$\text{5}\text{2}$})→E′(⁶H_{$\text{1}\text{2}$}) E_u′(⁶F_{$\text{1}\text{2}$}) no-phonon transition is postulated to be pure electric quadrupole allowed. The ground state magnetic moment is determined to be very small from magnetic circular dichroism (MCD) spectra.This study has led to the assignment of nearly all of the crystal field levels in the visible and IR region for Cs₂NaSmCl₆. A total of 27 such levels were identified, 17 from no-phonon transitions and the rest from vibronic transitions. The magnetic dipole intensity calculated using intermediate coupling O_h wavefunctions along with a crystal field analysis of the splitting pattern was used in the assignment of the levels. Vibronic bands were observed for all transitions and their vibrational symmetries were tentatively assigned. MCD data were used to determine the magnet moment of the ground state.     

Fluorescence quantum yields and cascade-free lifetimes of state selected CO+2, COS+, CS+2 and N2O+ determined by photoelectron—photon coincidence spectroscopy

The details and principles of an apparatus built for measurements of fluorescence quantum yields and cascade-free lifetimes of open-shell cations are reported. These rely on the detection of coincidences between energy selected photoelectrons and undispersed photons. The results of such measurements for CO⁺₂, COS⁺, CS⁺₂ and N₂O⁺ in selected vibrational levels of their excited states are presented. Non-unity fluorescence quantum yields are found for some vibronic levels of CO⁺₂($\text{B}$), COS⁺ ($\text{A}$), N₂OP⁺($\text{A}$) and a non-exponential decay is observed for CS⁺₂($\text{A}$). The data yield the following values for the radiative lifetimes: CO⁺₂($\text{A}$) 124 ± 6 ns, CO⁺₂($\text{B}$) 140 ± 7 ns, COS⁺($\text{A}$) 550 ± 50 ns and N₂O⁺($\text{A}$) 240 ± 12 ns.     

High-performance liquid chromatographic determination of the antitumor agent mitomycin c in human blood plasma

A high-performance liquid chromatographic method for the determination of the antitumor drug mitomycin C in blood plasma samples of cancer patients is described. The drug is extracted from the plasma with chloroform–2-propanol (1+1, $\text{w}\text{w}$) and chromatographed on a reversed-phase column with u.v. detection at 365 nm. The detection limit of the determination is 1 ng ml^-1 for 0.2–1.0 ml plasma samples. Preliminary results of a pharmacokinetic study show that the sensitivity and selectivity of the assay are adequate for drug monitoring in clinical practice. The results obtained from multiwavelength detection suggest the existence of metabolites.     

Über Ordnungs-Unordnungsphänomene bei Sauerstoff perowskiten vom Typ A2+3B2+M5+2O9

Perovskites of the type A²⁺₃B²⁺M⁵⁺₂O₉, where A²⁺ = Ba, Sr; B²⁺ = Mn, Co, Ni, Zn; M⁵⁺ = Nb, Ta, show order-disorder phenomena. At lower temperatures a thermodynamically unstable disordered cubic perovskite is formed ($\text{1}\text{3}$ formula unit—$\text{AB}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{M}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{O}{}_3$—in the cell), which transforms irreversibly into a 1: 2 ordered high-temperature form with 3L structure (sequence (c)₃). For A²⁺ = Ba this lattice is hexagonal (space group $\text{P}\text{3}\text{m1}$; one formula unit in the cell); with A²⁺ = Sr a triclinic distortion is observed. For Ba₃CoNb₂O₉ a second transformation into a cubic disordered perovskite takes place at 1500°C. This transition is reversible and of the order-disorder type. The vibrational and diffuse reflectance spectra are discussed.     

Yield of I(2Psol:12) in the photodissociation of CH2I2

The production of I(²P_{$\text{1}\text{2}$}) in the photolysis of CH₂I₂ has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm^?1 correlate with I(²P_{$\text{3}\text{2}$}) whilst those at 34700 and 40100 cm^?1, which correlate with I(²P_{$\text{1}\text{2}$}), give final ²P_{$\text{3}\text{2}$}/²P_{$\text{1}\text{2}$} ratios of 1.75 and 1.1, respectively, after curve crossing.     

The structure of a carbon monoxide adduct of cobalt-exchanged zeolite A (Co5.25Na1.5A · 1.5CO) by neutron profile refinement

The structure of a carbon monoxide adduct of cobalt-exchanged zeolite A, CO_5.25Na_1.5A · 1.5CO, has been determined by Rietveld neutron profile refinement. The space group used was $\text{Fm}\text{3}\text{c}$ with a = 24.1557(14) Å; the final R_pw was 13.8%. All exchangeable cations are located in sites adjacent to the 6-rings; 3.75 of the cobalt cations sit 0.4 Å inside the β-cage (Co(2)) and are arranged tetrahedrally about the eight 6-ring sites in the β-cage. The sodium cations (Na(1)) reside just inside the α-cage in sites similar to those found previously for zeolites 3A, 4A, and 5A. The remaining 1.5 cobalt cations (Co(1)) are located in sites similar to those for sodium, but they are also coordinated to the carbon monoxide molecules, which lie on, or close-to, the threefold axis which passes through the 6-ring. Inside the β-cage there is a tetrahedral aluminum complex of AlO₄ type, the oxygen atoms (O1) of which point toward six rings not occupied by cobalt cations, Co(2). Each of the oxygen atoms of this complex is involved in a hydrogen bond (2.83 Å) to the 6-ring oxygen O(3). Approximately $\text{2}\text{3}$ of these bonds are of type O1H···O(3) and $\text{1}\text{3}$ of type O1···HO(3).     

Kinetic spectroscopy in the far vacuum ultraviolet. Part I: Detection of (2p5) 2P32,12 fluorine atoms using atomic resonance spectrometry in the wavelength range 95–98 nm

A new experimental system for atomic resonance spectrometry at λ < 105 nm in a discharge-flow system is described. The spectrum of a fluorine resonance lamp has been studied, and possible precursors for the 2p⁴ 3s excited F atoms formed are suggested. Ground state (2p⁵²P_{$\text{3}\text{2}$}) and J-excited ²P_{$\text{1}\text{2}$} F atoms have been detected for the first time in resonance absorption and fluorescence using the first resonance transitions with wavelengths between 95.2 and 97.8 nm. Preliminary measurements (using both ⁴P-²P and ²P-²P lines) of the variations with concentration of absorption intensity by ground state F ²P_{$\text{3}\text{2}$} and by J-excited F ²P_{$\text{1}\text{2}$} atoms are reported; F atom concentrations were measured using a titration method based on the rapid reaction, F + Cl₂ → FCl + Cl.     

The chemical oxidation and electronic spectra of the complexes trans-[M(CNR)2(Ph2PCH2CH2PPh2)2] (M = Mo or W)

Oxidation of the complexes $\text{trans}$-[M(CNR)₂(dppe)₂] (A) (M = Mo or W; R = Me, Bu^t or CH₃C₆H₄-$\text{4}$; dppe = Ph₂PCH₂CH₂PPh₂) with diiodine or silver (I) salts gives the paramagnetic cations $\text{trans}$-[M(CNR)₂(dppe)₂]⁺, (M = Mo, R = CH₃C₆H₄-$\text{4}$; M = W, R = Bu^t) and $\text{trans}$-[M(CNR)₂(dppe)₂]²⁺ (M = Mo, R = Me or CH₃C₆H₄-$\text{4}$; M = W, R = Me or Bu^t). Mixtures of products are generally produced when dichlorine or dibromine are the oxidising agents, however pure salts, the seven-coordinate complex cations [MX(CNC₆H₄CH₃-$\text{4}$)₂(dppe)₂]⁺ (B, X = Cl or Br) have been isolated. A simple molecular orbital scheme is proposed for complexes (A) and used to discuss their electronic spectra and their oxidation.     

Darstellung ylidischer metallacyclopropankomplexe durch ringverkleinerung metallacyclischer vinylketonkomplexe. Molekülstruktur von C5H5W(CO)2[(PMe3)HC-CH(COMe)]

The addition of trimethylphosphane to five-membered metallacyclic vinylketone complexes of the type Ar$\text{M(CO)}{}_2\text{(HCCHCO}$R) (I) (Ar = η⁵-aromatic ring system: C₅H₅, C₅H₄Me, C₅Me₅; R = Me, Et, n-Bu; M = Mo, W) in pentane solution results in the formation of the ylidic metallacyclopropane complexes Ar$\text{M(CO)}{}_2\text{[(PMe}{}_3\text{)-HCC}$H(COR)] (II). In these 1:1 adducts the three-membered ring is stabilized by an electron-donating phosphonium and an electron-attracting acyl substituent. The negative charge in the ylidic complexes II is localized on the central metal providing it with Lewis base properties. An extraordinary high electron density can be observed on the metal of the derivative C₅H₅$\text{W(CO)(PMe}{}_3\text{)[(PMe}{}_3\text{)HCC}$H-(COMe)] (III) which is formed by a 1:2 addition of C₅H₅W(CO)(C₂H₂)-(COMe) and PMe₃. The metallacyclopropane complexes II and III are characterized by IR, ¹H NMR, ¹³C NMR, ³¹P NMR and mass spectroscopy. For C₅H₅$\text{W(CO)}{}_2\text{[(PMe}{}_3\text{)HCC}$H(COMe)], the results of an X-ray structure determination are presented.     

Molecular predissociation dynamics revealed through multiphoton ionisation spectroscopy. III. New 1A2 and 1B1 rydberg states in H2S D2S

Two new Rydberg series in H₂S and D₂S habe been characterized as three-photon resonances in four-photon ionisation spectrometry. Members of the two series exhibit sufficient rotational structure to permit characterisation of their electronic symmetries as, respectively. A₂ and B₁. The first Rydberg series is identified with the (one-photon forbidden) excitations npb₂ ← 2b₁ (¹A₂ ← $\text{X}$¹A₁) on the basis of the observed quantum defects. Geometry considerations indicate that second series, of ¹B₁ states, also arises as a result of electronic promotion from the highest occupied 2b₁ orbital. The acceptor (a₁) Rydberg orbitals possess substanial s character, but the polarisation dependence of the various ¹B₁-$\text{X}$¹A₁ three-photon transition probabilities their hybrid I character, d (and quite possibly p) functions contribute also. The results provide further clear demonstration of the way in which multiphoton excitations, and MPI techniques in particular, can complement conventional one-photon absorption techniques. Members of both series are predissociated. Vibronic predissociation rates are found generally to decline with increasing n and to be slower in D₂S than in H₂S. The lowest (n = 4) member of the ¹A₂ series in both isotopic species appears immune from rovibronic predissociation but higher members show evidence of a ($\text{J}$_a²)-dependent rotationally-induced predissociation, the severity of which increases dramatically with n. This observation is explained in terms of electronic-rotational Coriolis coupling to a dissociated ¹B₂ state is presumed to be responsible for the observed ($\text{J}$_b²)-dependent heterogeneous predissociation of the ¹B₁ (n = 6) member in H₂S. However, the dominant rotationally-induced predissociation mechanism that affects the counterpart in D₂S scales with ($\text{J}$_a²). Wherever possible comparisons are drawn with the known spectroscopy and photophysics of the isovalent molecules H₂O and D₂O.     

Tunable laser photodissociation: quantum yield of I★(2P12) from Ch2I2

Tunable laser I^★(²P_{$\text{1}\text{2}$}) quantum-yield measurements are presented for CH₂I₂ in the wavelength range 248–340 nm. The results suggest that a curve-crossing mechanism is operative in the dissociation.     

Etude à haute pression des tétramétaphosphates du type M2P4O12 (M = Ni,Mg, Cu,Co, Fe,Mn, Cd). Données cristallographiques sur tous les composés M2P4O12

Fe₂P₄O₁₂ has been prepared and identified as an isotype of the other M^II₂P₄O₁₂ tetrametaphosphates (M^II = Ni, Mg, Cu, Co, Mn, Cd). Its monoclinic unit cell:

$\text{a=11.952,b=8.359,c=9.932}\text{A}\text{?}$

$\text{β=118°76}$

contains 4 formula units. The space group is $\text{C2}\text{c}$. For tetrametaphosphates with M^II = Ni, Mg, Cu, Co, and Mn we found a new denser phase induced at 80 kbar and 1000°C. In the case of Fe₂P₄O₁₂ the unit cell of this new form is

$\text{a=9.777,b=8.994,c=4.968}\text{A}\text{?}$

$\text{β=107°22}$

with Z = 2 and two possible space groups Cc or $\text{2C}\text{c}$. This dense phase exists at ordinary pressure for the zinc salt.     

Far-infrared laser magnetic resonance spectrum of SeD (X2Π32)

Far-infrared laser magnetic resonance (LMR) spectra of SeD have been detected at 513 μm using a formic acid laser, and assigned to Zeeman components of the J = $\text{3}\text{2}$ → $\text{5}\text{2}$ transition in the six isotopic forms ^{82,80,78,77,76,74}SeD. Analysis yields the following B_o constants (cm^?1): ⁸²SeD 3.96047, ⁸⁰SeD 3.96284, ⁷⁸SeD 3.96532, ⁷⁷SeD 3.96657, ⁷⁶SeD 3.96793 and ⁷⁴SeD 3.97066. These values, combined with B_o for ⁸⁰SeH from 5.6μm LMR, yield r_e = 0.14634 nm for SeD.