Were J. Kepler and O. Krötenheerdt right?

It is established that one of the 12 Kepler nets (R, 3366 + 3636) belongs to Krötenheerdt nets. However, the number of Kepler nets remains 12, because one of them (L, 33336) is enantiomorphic. Along with 20 Krötenheerdt nets, there may be many other polytypes which enter infinite sequences of the O, OD, DO, D types.     

Glass transition and specific heats in the systems PS,PSe,AsS and AsSe

The glass transition temperatures were measured in the systems AsS, As_0.5P_0.5S, PSe, AsSe and PAsSe. Heat capacities of the glasses in the selenium systems were obtained by differential scanning calorimetry. As shown by the residual entropies departures from ideality are high in the chalcogen glasses. The results are discussed in terms of the structure of glasses in these systems. The thermodynamic data of glasses and liquids in these systems indicate a balance of intra- and intermolecular saturation of bonds. The amount of polymerization increases with increasing average molecular weight in the glass and with increasing temperature in some of the investigated liquids.     

Anticancer agent development. 5. X-ray structure and1H nmr spectral analysis of (1α,2α,5α,6α)-2,6-bis(3,4-methylenedioxyphenyl)-3,7-dioxabicyclo[3.3.0]octane-4,8-dione

The title compound, C₂₀H₁₄O₈, Mr=382.3, crystallized from chloroform in the centric space group P¯1 witha=6.516(4),b=6.798(3),c=9.545(7) Å,=85.31(5),=73.87(5), =79.59(4)°,V=399.2 ų, and D_calc=1.59 g cm^–3 forZ=1. Least-squares refinement of 1035 observed [F_o5(F_o)] reflections led to the final agreement index ofR=0.074. The molecule resides on a crystallographic center of inversion and is disordered into two different conformations. This manifests itself as a 50/50 disorder at O(4), C(2), and C(3). The observed structure reveals acis relationship between the bridgehead hydrogen atoms and the aryl rings. The 90 MHz¹H nmr spectrum of the title compound exhibits an AAXX spin system with a H(1)C(2) to H(1)C(3) and H(1)C(2) to H(1)C(3) coupling constant of 2.8 Hz. Computer spectral simulation and Karplus equation analysis are utilized to illustrate a relaxation of the torsion angles between H(1)C(2) and H(1)C(3), and H(1)C(2) and H(1)C(3) is solution.     

Quantitative UV–VIS spectroscopic studies of photo-thermo-refractive glasses. I. Intrinsic,bromine-related,and impurity-related UV absorption in photo-thermo-refractive glass matrices

The paper opens up a series of papers on the origin and parameters of spectral features forming the absorption of photo-thermo-refractive (PTR) glasses in the UV. Problems to be cleared for gaining further insight into the spectroscopic manifestations of species responsible for the photo-induced processes in PTR glasses are discussed. The samples of bromine-containing and bromine-free PTR glass matrices are synthesized and their absorption spectra in the 28,500 to 50,000 cm^–1 region are recorded. The dispersion analysis of the spectra is conducted based on the convolution model for the complex dielectric function of glasses. The matrix electronic transitions that set the real part of the complex dielectric function and form the intrinsic absorption tail of the matrix are simulated with a series of effective oscillators. Spectral features forming the total absorption spectrum of PTR glass matrices in the 28,500 to 50,000 cm^–1 region are deconvoluted. These features are (i) the intrinsic absorption tail, (ii) for the bromine-containing matrix, the low-wavenumber wing of an envelope around ~ 51,400 cm^–1 covering the bromine-related spectral feature(s), (iii) Fe²⁺- and Fe³⁺-related impurity bands, and also (iv) a structureless absorption mostly due to the high-wavenumber wings of other impurity bands below 28,500 cm^–1.     

Substituted cyclopentadienyl complexes. 5. Crystal and molecular structure of [(η5-C5H4Me)Fe(CO)(L)I] [L = 2,6-Me2C6H3NC,P(OMe)3, and P(C6H11)3]

The crystal and molecular structures of three derivatives of [( ⁵-C₅H₄Me)Fe(CO)(L)I] [L=2,6-Me₂C₆H₃NC, P(OMe)₃, and P(C₆H₁₁)₃] have been determined. [( ⁵-C₅H₄Me)Fe(CO)(CNC₆H₃Me₂-2,6)I] (1): Space groupP¯1,Z=2,a=13.193(7),b=8.183(5),c=7.465(4) Å,=95.13(5),=94.39(5), =91.09(5)°. [( ⁵-C₅H₄Me)Fe(CO)[P(OMe)₃]I] (2): Space groupP2₁/c,Z=4,a=7.296(3),b=24.471(6),c=8.877(3) Å,=111.92(4)°. [( ⁵-C₅H₄Me)Fe(CO)[P(C₆H₁₁)₃]I] (3): Space groupP2₁/c,Z=4,a=9.809(3),b=14.147(2),c=8.276(3) Å,=103.07(2)°. The structures were refined toR values of 0.045, 0.070, and 0.061, respectively. Disorder was observed in the P(OMe)₃ ligands on2. Structural data for1 and3 reveal (i) a small movement of the Fe atom away from the ringC atom containing the methyl group, (ii) a larger movement of ring C atoms away from the ring least-squares plane for3 than for1, and (iii) a shift toward an allyl-ene bond length variation in the ring distances for3. Molecular mechanics calculations performed on2 produce a low-energy conformation similar to that found in the crystal structure determination of2 with an energy barrier to ring rotation of ±5 kcal mol^–1. A correlation of the structural and molecular mechanics data with the nmr spectra of complexes1 to3 indicates that the steric influence ofL on the ring rotation could be due to ring distortion and/or interaction with the ring methyl group.     

Crystal structure ofβ-C.I. Solvent Yellow 18, 4(2′,4′-dimethylphenyl hydrazono)-5-methyl-2-phenyl-3H-pyrazol-3-one

The crystal structure of-C.I. Solvent Yellow 18, C₁₈H₁₈N₄O, has been determined by single crystal X-ray diffraction techniques. It crystallizes in the monoclinic system witha=30.948(18)Å,b=4.918(4)Å,c=20.861(9)Å,=91.68(4)°, space groupC2/c,Z=8. The structure has been solved by direct methods and least-squares refinement has been completed on three dimensional data (1237 reflections MoK radiation). The hydrogen atoms have been found but only their positional parameters refined. Final residual 0.092 (all intensity data). The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonding keeps the molecule approximately planar. The molecules are packed in columns parallel to theb axis, while the molecule lies approximately parallel to the (51¯3) plane. The molecules are linked by van der Waals' force.     

Crystal structures of double vanadates, Ca9 R(VO4)7 ⋅ III. R = Nd, Sm, Gd, or Ce

The crystal structures of Ca₉ R(VO₄)₇ (R = Nd (I), Sm (II), or Gd (III)) were studied by the Rietveld method. The compounds are isostructural to Ca₃(VO₄)₂ and are crystallized in the trigonal system (sp. gr. R3c, Z = 6). The unit-cell parameters are as follows: for I, a = 10.8720(5) Å, c = 38.121(1) Å; for II, a = 10.8652(5) Å, c = 38.098(1) Å; and for III, a = 10.8631(5) Å, c = 38.072(1) Å. In the structures of I and II, the M(1), M(2), and M(3) positions are statistically occupied by the rare-earth cations and calcium anions. In the structure of III, the Gd³⁺ cations occupy the _M(1) and _M(2) positions. The distributions of the R ³⁺ cations over the positions are characteristic of each structure. The composition of the cerium-ontaining compound Ca_9.81Ce_0.42(VO₄)₇ (a = 10.8552(5) Å, c = 38.037(1) Å) was refined and its crystal structure was solved from the X-ray powder data. In this compound, cerium atoms are in the oxidation states +3 and +4.     

Complexation with diol host compounds. Part 19. Structures and thermal analyses of inclusion compounds oftrans-9,10-dihydroxy-9,10-diphenyl-9,10-dihydroanthracene with dimethylsulphoxide,diethylketone and (±)-2-butanol

The structures of the host compoundtrans-9,10-dihydroxy-9,10-diphenyl-9,10-dihydroanthracene with dimethylsulphoxide (12), diethyl ketone (11) and (±)-2-butanol (11) have been elucidated. Each compound is stabilized by O–H...O hydrogen bonds between host and guest, and the guest molecules are disordered in each structure. The thermal decomposition of the compounds shows them to be relatively unstable.     

Synthesis of 1 - (4-Alkoxy or Alkyl- Benzoyloxy-Phenyl) - 2- (4′- Pentylphenyl) - Ethanes. Influence of the Central Group on the Mesomorphic Properties

An homologous series of mesomorphic compounds, the I-(4-alkoxy or alkyl-benzoyloxyphényl)-2-(4′-pentylphenyl)-ethanes, has been synthesized. The compounds with R = alkyl have low-melting points and wide mesomorphic ranges, for example from 33.5°C to 106.5C. The compounds with R = alkoxy exhibit a smectic polymorphism; for example a compound of this series is successively smectic B, F and C. The influence of the central linkage when the ethane group is replaced by an ester, single bond, ethylene, azomethine, azo, methylenecetone or cetone groups, is discussed.     

Stereospecific Ligands and Their Complexes. III. Oxalato and Malonato-(ethylenediamine- N , N ′-di- S , S -2-propionato)-Chromate(III) Complexes. Crystal Structure of the Δ-(–)589- s - cis -K[Cr( S , S -eddp)(ox)]?·?0.5H2O

Abstract  The s-cis-[Cr(S,S-eddp)L]⁻ complexes (S,S-eddp = S,S-ethylenediamine-N,N′-di-2-propionate ion; L = oxalate or malonate ions) were prepared. The complexes were purified by ion-exchange chromatography. The geometry of the complexes has been supposed on the basis of the electronic absorption spectra, and the absolute configurations of the isolated s-cis-[Cr(S,S-eddp)L]⁻ complexes have been predicted on the basis of their circular dichroism (CD) spectra and confirmed by X-ray analysis of the crystal structure of the Δ-(–)₅₈₉-s-cis-K[Cr(S,S-eddp)(ox)] 0.5H₂O complex. Index Abstract  The title compound, s-cis-potassium-(ethylenediamine-N,N’-di-S,S-2-propionato) (oxalato)chromate(III) semihydrate was synthesized by passing the corresponding sodium salt through cation exchange-resin Merck I in potassium form and its crystal structure determined. Single crystal X-ray diffraction analysis reveals s-cis geometry of the complex cation. For Part II see Glodjović VV, Trifunović SR (2008) J Serb Chem Soc 73:541.