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.     

Solid solution formation in chalcopyrite systems of the type AgInX2AgMIIIX2 where M = Al,Ga, and X = S,Se

Previous (1) work on ternary chalcopyrite solid solution formation has shown that the difference in end point axial ratios ($\text{Δc}\text{a}$) is an important factor in determining the extent of mutual solubility. It was concluded that when $\text{Δc}\text{a}\text{> 0.13}$ complete solid solubility will not occur. In this work it is shown that complete solid solution formation in the systems AgAlS₂AgInS₂ ($\text{Δc}\text{a}\text{= 0.111}$), AgGaS₂AgInS₂ ($\text{Δc}\text{a}\text{= 0.11}$) and AgAlSe₂AgInSe₂ ($\text{Δc}\text{a}\text{= 0.112}$) does occur. This shows that the value of $\text{Δc}\text{a}\text{= 0.13}$ as an upper limit for solid solution formation can be approached closely.     

The crystal structure of Ca6Eu2Na2(PO4)6F2

The crystal structure of Ca₆Eu₂Na₂(PO₄)₆F₂ has been determined by single crystal X-ray diffraction. The unit cell constants are $\text{a = 9.385(2), c = 6.893(3)}\text{A}\text{?}$ and the space group is $\text{P6}{}_3\text{m}$. The structure was refined by normal full matrix least squares techniques. The final value of the refinement indicator is R = 0.065, based on 419 reflections.The structure of Ca₆Eu₂Na₂(PO₄)₆F₂ contains disordered cations in both the triangle and column positions. The occupation of the six triangle sites is $\text{1}\text{4}\text{Eu}$ and $\text{3}\text{4}\text{Ca}$ and of the four column sites $\text{1}\text{2}\text{Na}\text{,}\text{4}\text{10}\text{Ca}$, and $\text{1}\text{10}\text{Eu}$.     

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.     

Conformation,in solution,of c-4-t-butyl-1-phenyl-r-1-(N-piperidyl)cyclohexane hydrochloride. The conformational energy of t-butyl

Although the hydrochloride of $\text{c}$-4-$\text{t}$-butyl-1-phenyl-$\text{c}$-1-(N-piperidyl)cyclohexane crystallizes in the conformation with axial $\text{t}$-butyl, it exists as an almost equimolar mixture of the two chair conformers in CD₂ Cl₂ solution. The position of equilibrium allows one to calculate ΔG°_{$\text{t}$-Bu} as ?4.9 kcal/mol.     

Observation of nonlinearity and asymmetry in energies of EPR transitions of 160Gd3+ in La(C2H5SO4)3 · 9D2O at low magnetic fields

The energies of EPR transitions of ¹⁶⁰Gd³⁺ in La(C₂H₅SO₄₃ · 9D₂O at 77.2 K are observed to be nonlinear functions of field at low fields. The + $\text{3}\text{2}$, + $\text{1}\text{2}$ and ?$\text{3}\text{2}$, ?$\text{1}\text{2}$ transition energies converge asymmetrically below 10 G and differ by only ≈ MHz at the lowest fields employed.     

Acid-catalysed decomposition of (20 R) and (20 S)-20-azido-5α-pregnane : bis steroids Schiff base formation via imine coupling.

BF₃-OEt₂ decompostion of azides $\text{1}$ or $\text{2}$ leads to the coupling product Schiff base $\text{6}$$\text{via}$ imine intermediates.     

Crystallography and phase relations of MeOM2O3TiO2 systems (Me = Fe,Mg, Ni; M = Al,Cr, Fe)

Subsolidus phase relations of ternary oxide systems containing divalent Fe, Mg, or Ni, trivalent Al, Cr, or Fe, and tetravalent Ti are characterized by solid solutions at metal/oxygen ratios $\text{3}\text{4}$, $\text{2}\text{3}$, and $\text{3}\text{5}$. At low temperatures only compounds with cubic or hexagonal close-packed oxygen and uniform oxygen coordination remain stable in the crystal structures NaCl, spinel, ilmenite-α-Al₂O₃, TiO₂. The pseudobrookite phases FeTi₂O₅, MgTi₂O₅, Al₂TiO₅, Fe₂TiO₅, the V₃O₅ structure phase Cr₂TiO₅, and the Andersson phases Cr₂Ti_n?2O_2n?1 (n = 4,6,7,8,9) decompose. Additional phases with close-packed oxygen as predicted by a simple structure model for metal/oxygen ratios $\text{7}\text{12}$, $\text{5}\text{6}$, and $\text{11}\text{12}$ do not form but presumably are important for nonstoichiometric solid solutions. Most differences between systems containing transition metals and the MgOAl₂O₃TiO₂ system can be attributed to crystal field effects.     

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.     

On the mechanism of the formation of benzocyclobutene by flash vacuum pyrolysis of ortho-methylbenzyl chloride

Flash vacuum pyrolysis of $\text{o}$-methylbenzyl chloride-$\text{∝}$,$\text{∝}$-$\text{d}$₂ gives benzocyclobutene-$\text{∝}$,$\text{∝}$-$\text{d}$₂. This finding indicates that the reaction involves net δ-elimination of hydrochloric acid.     

Organothiometallate - alkyne addition products. The crystal and molecular structure of [(η5-C5H5)W{C(CO2Me)C(CO2Me)C(O)SMe} (CO)2]

The title compound is the final product of the reaction between dimethylacetylene dicarboxylate and [(η⁵-C₅H₅)W(SMe) (CO)₃ ]. Its molecular structure has been established by an $\text{x}$-ray analysis based on 3301 diffractometric intensities. The crystals are monoclinic, space group $\text{P}$2₁/$\text{a}$, with four molecules in a cell of dimensions $\text{a}$ = 10.323(2), $\text{b}$ = 16.016(2), $\text{c}$ = 10.437(2)», β = 103.56(2)°. After least-squares refinement $\text{R}$ = 0.036. The tungsten co-ordination is square-pyramidal, the apical site being occupied by the centroid of the cyclopentadienyl ring. The basal co-ordination sites contain two carbonyl groups and also the sulphur and σ-bonded carbon atoms of a chelating carbothiolic methyl ester ligand derived from the incoming alkyne and CO and SMe groups of the original complex. The W-S and σ-W-C bond lengths are 2.440(2) and 2.194(7)».     

Reversible nethide shifts in the 2-tert-butyl-2-adamantyl cation

Treatment of either 3-$\text{tert}$-butyl-2-adamantanol or 2-isopropenyl-2-methyladamantane with acid in the presence of a reducing agent (hydrogen iodide or tri-$\text{2}$-hexylsilane) yielded 2-$\text{tert}$-butyladamantane as the major or exclusive product. Both precursors gave the 2-$\text{tert}$- butyl-2-adamantyl cation at ?78°C in FSO₃H-SbF₅-SO₂ClF.     

Heat capacity and thermodynamic properties of ramsdellite,Li2Ti3O7, and spinel,Li43Ti53O4

The heat capacity and heat content Li_{$\text{4}\text{3}$}Ti_{$\text{5}\text{3}$}O₄ and Li₂Ti₃O₇ have been measured in the temperature range 198—960 K. The lattice and dilation contributions to the heat capacity have been estimated. The standard thermodynamic functions and the high temperature enthalpy and entropy have been derived. The lattice heat capacity of Li_{$\text{4}\text{3}$}Ti_{$\text{5}\text{3}$}O₄ spinel appears to be consistent with the phonon model put forward by Grimes.     

Epoxidation with the H2O2/vilsmeier reagent system

Alkenes $\text{1}$ a–d interact at ?80°C in 15 min. with the Vilsmeier reagent $\text{I}$ (Me₂N=CHCl)⁺PO₂Cl₂^? in presence of 30% H₂O₂ to yield the corresponding epoxides $\text{3}$ a–d. The reaction could involve the formation of the highly reactive hydroperoxymethylenedimethylammonium salt (Me₂N=CHOOH)⁺PO₂Cl^?₂$\text{II}$.     

Synthesis of N-benzoyl L- and D-2,3,6-trideoxy-3-aminoxylo-hexose from non-carbohydrate precursors

The enantiomeric alcohols ($\text{2}$) and ($\text{11}$), obtained from (2$\text{R}$,3$\text{R}$) tartaric acid and, respectively, $\text{L}$-threonine, have been used to construct the C₆, enantiomeric deoxy amino sugar derivatives ($\text{7}$) and ($\text{12}$)     

Molecular predissociation dynamics revealed through multiphoton ionisation spectroscopy. I. The C1B1 states of H2O and D2O

The $\text{C}$¹B₁ states of H₂O and D₂O have been observed by means of three photon absorption (four photon ionisation) spectroscopy. Differences between the experimentally observed 3 + 1 multiphoton ionisation spectrum and that predicted by the appropriate asymmetric-top three-photon line-strength theory are attributed to $\text{C}$ state predissociation. Two separate predissociation mechanisms have been identified, one (heterogeneous) relying on a-axis parent molecular rotation to couple the bound B₁ state to an unbound state of A₁ electronic symmetry, the other (homogeneous) involving a second, dissociative excited electronic state of B₁ symmetry. Having established the detailed $\text{C}$ state predissociation dynamics, two photon absorption spectra of H₂O and D₂O ($\text{C}$ ← $\text{X}$) can be predicted accurately: studies of individual quantum-state-selected photofragmentation processes from H₂O($\text{C}$) are proposed.     

Isolation of aspirochlorine (=antibiotic A30641) possessing a novel dithiodiketopiperazine structure from Aspergillus Flavus

A very unusual dithiokikeptopiperazine structure ($\text{1}$) has been assigned to aspiroclorine, C₉H₁₂N₂O₅S₂Cl, produced as a biologically active substance together with canadensolide by $\text{Aspergillus}$$\text{flavus}$, which has been found to be identical with the antibiotic A 30641 from $\text{A.}$$\text{tamarii}$.     

Boat-chair conformational preference of exo, exo-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid

The ¹H and ¹³C nmr spectra of $\text{exo}$, $\text{exo}$-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d₆ or alkaline D₂O, clearly show that it exists in a $\text{boat}$-$\text{chair}$-conformation with $\text{equatorial}$ carboxyl groups, thus being the first case of $\text{boat}$-$\text{chair}$ preference of a bicyclo[3.3.1] nonan-9-one due to the presence of $\text{exo}$,$\text{exo}$-2,4- substituents.     

Synthesis of N-benzoyl-L-daunosamine from D-threonine

The synthesis of N-benzoyl-$\text{L}$-daunosamine (14) from the C₄$\text{threo}$ aldehyde (2b), prepared from $\text{D}$-threonine, through the intermediacy of the C₇ adduct (7a) is reported     

Cis-trihetero-tris-σ-homobenzenes as tridentate ligands - X-ray crystal. Structure analyses of the Co(C6H9N3)2(NO3)3 and Ba(C6H6O3)4(ClO4)2-complexes

According to X-ray crystal structure analyses “cis-benzenetrisimine” ($\text{2}$) and “cis-benzenetrioxide” ($\text{1}$) act as tridentate ligands in their 2:1- and 4:1-complexes $\text{7}$ (Co(C₆H₉N₃)₂(NO₃)₃) and $\text{8}$ (Ba(C₆H₆O₃)₄(ClO₄)₂), resp. The latter is the rare example of an organic complex with the (approximate) T-symmetry.