Search

The structural behaviour of ammonium metavanadate, NH4VO3, under high pressures has been studied to 65 kbar using energy-dispersive synchrotron X-ray powder diffraction, and to 106 kbar by FTIR methods, in a diamond anvil cell. A reversible crystalline-to-disordered phase transition was found at 49 kbar. The transition is thought to be due to relative slipping of the vanadate chains parallel to their axes, the product being disordered, possibly amorphous, rather than crystalline because the process is hindered and the solid prevented from attaining periodicity by hydrogen bonding to ammonium ions.

A summary account is given of the phase transitions found at high pressure for several inorganic carbonyl and cyanide complexes: M(CO)6, (M = Cr, Mo, W); Re(CO)5Br; M2(CO)10, (M = Mn, Re) and MnRe(CO)10; Hg(CN)2; K2M(CN)4, (M = Zn, Cd, Hg); and K3Cu(CN)4. The structures of some of the phases have been deduced using group theoretical methods.

Ultrahigh temperature sterilized canned puddings occasionally exhibit spoilage in the form of a dramatic loss of viscosity or thinning. Studies on a concentrated fraction of spoiled pudding indicate that thinning was due to a heat-resistant amylase. The concentrate was obtained by centrifugation and ultrafiltration of the thinned pudding. Ultrafiltration characteristics of the active agent indicate a molecular weight of 1–30 × 104 daltons. The agent attacked starch with a decrease in iodine-binding capability and an increase in reducing units. Treatment of the concentrate with proteolytic enzymes decreased enzymatic activity by 50%; treatment with sodium ethylene diaminetetraacetate decreased activity by 80%. The levels of starch and pH of the spoiled puddings were suitable for action of the amylase, and the enzyme was quite active at normal and elevated room temperatures.

The α-amylase of the thermophile Bacillus stearothermophilus 1518 was used as a model enzyme to examine the heat resistance of a bacterial amylase at ultrahigh temperature in a starch-based pudding. When heated in the laboratory pudding at 143°C for the equivalent of 22.2 set, approximately 26% of the initial amylolytic activity was retained. The presence or absence of individual ingredient groups (starch, caseinate-nonfat dry milk, oilemulsifiers, salts, or sucrose) of the pudding had no significant effect on amylase heat resistance. A combination of any two of the starch, caseinate-nonfat dry milk, or oil-emulsifier ingredients were found to be important for thermostability. The amylase of the mesophile Xanthomonas campestris 13957–2 exhibited similar thermal inactivation characteristics.

Potassium nitrate (KNO3) has seven polymorphs in the pressure range 0-4.0 GPa. The authors have studied it at room temperature as a function of pressure up to 9.3 GPa and have confirmed the structure of phase IV previously refined by neutron diffraction at 0.36 GPa. The compressibility measured in the range 0.3-9.3 GPa is found to be anisotropic with the axial compression ratios a:b:c=1.0:0.64:0.50. The relative merits of X-rays and neutrons for high-pressure studies are discussed.

Phase transitions have been observed in mercury (II) cyanide near 2.5, 89, 19 and 60 kbar. The I/II transition appears to be of second order with the structure of phase II closely related to that of the parent molecular type. Using Landau theory, three possible structures have been identified for the new phase II, of which S24 is marginally better in accord with the evidence. A major reconstruction of the lattice occurs at the II/III transition; the coordination number of mercury appears to increase to four, and the structure becomes covalently bonded, rather than molecular. Phase IV has a spectrum consistent with it having the cubic anti-cuprite structure adopted at STP by Zn(CN)2 and Cd(CN)2. Above 60 kbar, brown polymeric Hg(CN)2V is formed irreversibly. It has a single IR absorption

Clostridium perfringens spores were injured by ultrahigh-temperature treatment at 105 C for 5 min. Injury was manifested as an increased sensitivity to polymyxin and neomycin. Since many of the survivors could not germinate normally the ultrahigh-temperature-treated spores were sensitized to and germinated by lysozyme. Polymyxin reportedly acts upon the cell membrane. Neomycin may inhibit protein synthesis and has surface-active properties. Injured spores were increasingly sensitive to known surface-active agents, sodium lauryl sulfate, sodium deoxycholate, and Roccal, a quaternary ammonium compound. Injured spores sensitive to polymyxin and neomycin also were osmotically fragile and died during outgrowth in a liquid medium unless the medium was supplemented with 20% sucrose, 10% dextran, or 10% polyvinylpyrrolidone. The results suggested that a spore structure destined to become cell membrane or cell wall was the site of injury. Repair of injury during outgrowth in the presence of protein, deoxyribonucleic acid, ribonucleic acid and cell wall synthesis inhibitors was consistent with this hypothesis.

Raman spectra of NaNO2 have been studied as a function of hydrostatic pressure to 40 kbar at 295 and 348 K. Slight changes in slope of mode frequency versus pressure plots support the view that a structural anomaly exists at 9 ± 1 kbar. The absence of qualitative changes in the Raman spectra allow the space group of NaNO2 IV to be specified as one of P1, P2, B2, Pm or Bm. The Raman spectrum of NaNO3 has been studied to 87 kbar. The changes observed are fully consistent with a second-order transition to a phase with symmetry C63v, as indicated by previous X-ray work, although the transition is sluggish.

The effect of pressure at low temperature (166.8K) upon the R1 and R2 lines of ruby has been investigated for the first time to establish a calibration for use in high-pressure/low-temperature work. A reinvestigation of the behaviour of R1 and R2 at ambient temperatures and at pressures up to ca 70 kbar supports previous work on the calibration under hydrostatic conditions but shows that in a 4:1 methanol:ethanol mixture conditions become nonhydrostatic at lower pressures (ca 50 kbar) than claimed (ca 100 kbar). The importance of monitoring both R1 and R2 is emphasised as their relative shifts are sensitive indicators of the presence, and approximate magnitude, of non-hydrostatic stress components. It is shown that although changes in half-bandwidths are also associated with development of shear stress, their use in estimating gradients is extremely hazardous and can indicate values greatly in excess of the known shear strength of the material.

Raman spectra have been obtained for HgCl2 to 145 kbar and HgBr2 to 100 kbar and phonon pressure dependencies established. The phase transition in HgCl2 said to be at 6.5 kbar, on NQR evidence, has been located at 2.2 kbar. A new first-order phase change has been found in HgCl2 at 79.0 kbar. Also in HgCl2, there are two bands that pressure scan differentially such that one overtakes the other, but they do not appear to be in resonance. Improved values for the phase transitions in HgBr2 are 4.0, 26.0 and 41.0 kbar. It is suggested that there are no structural equivalences between the two series of four polymorphs based upon the chloride and bromide respectively.

Raman and far-i.r. spectra are reported and assigned for the solid complexes Cr(CO)3(π-arene)(arene = benzene, aniline, toluene, methyl benzoate, anisole, and hexamethylbenzene) and M(CO)3(π-mesitylene)(M = Cr, Mo, or W). For the benzene complex, discussion is based upon the factor group, but in the other cases the molecular point-symmetry proves to be an adequate approximation. C3v local symmetry is an inadequate approximation when discussing the skeletal modes of complexes of monsubstituted arenes.

The O—H stretching frequency for methanol in the system methanol + dichloromethane + tetra-alkylammonium perchlorate is almost equal to that for a band which appears when perchlorate salts are dissolved only in methanol. The band is therefore assigned to methanol molecules hydrogen-bonded to perchlorate anions. A band which appears in the spectrum of HOD in H2O when perchlorates are added is, by analogy, similarly assigned. Other arguments against a previous theory that, for aqueous solutions, this band is due to free OD groups, are advanced. The influence of the cation upon the band for solvent molecules not associated with perchlorate ions is discussed.

The far-infrared spectra (70–400 cm.–1) of 36 thiourea and ethylenethiourea (imidazolidine-2-thione) complexes, embracing several different stereochemical types, are assigned and discussed. Metal–sulphur stretching frequencies, v(M–S), lie in the range 298–205 cm.–1 for the transition-metal complexes, and vary with co-ordination number and electron configuration in the manner now familiar from the behaviour of metal–hylogen stretching frequencies, v(M–X). For Group metals v(M–S) has been found as low as 170 cm.–1. The similarity between the spectra of thiourea complexes and those of thiocyanates has led to an assignment of the published data for thiocyanates. Some interesting variations in halogen-sensitive vibrations have been encountered.

Clostridium perfringens spores (three strains) were normally resistant to germination by lysozyme. In the absence of disulfide bond-breaking reagents, tetrasodium ethylenediaminetetraacetate rapidly sensitized the spores to lysozyme.

The ν(CO) spectra of Mo(CO)4 bipy (bipy = 2,2′-bipyridyl), cis-[W(CO)2{o-C6H4(PEt2)2}2],Cr(CO)3(π-mesitylene), and Cr(CO)3(π-C6H5·CO2Me) are examined in solution in n-hexane–chloroform or –nitrobenzene mixtures; the ν(NO) spectrum of Fe(NO)(S2CNMe2)2 is studied in benzene–nitromethane mixtures. Structure observed on the ν(CO) bands is discussed in terms of formation of solvent–solute complexes.

Spores of Clostridium perfringens NCTC 8798 became increasingly sensitive to inhibition by sodium chloride, sodium nitrite and a mixture of polymyxin and neomycin when heated at 70–100°C. That the increased sensitivity to each agent was caused by the same cellular damage was suggested by: (1) the temperature coefficients for induction of cellular damage leading to increased sensitivity to all three agents were the same; (2) in the absence of the agents, the spores regained resistance to all three at about the same time and in each case in the presence of cell wall-, protein- and DNA-synthesis inhibitors; (3) combinations of the agents were generally no more inhibitory to the heated spores than were the individual agents.

Hock and Stuhlman1 discovered that the reaction of iron pentacarbonyl with mercuric halides yielded solid products, which they formulated as addition compounds Fe(CO)4Hg·(HgX2), containing the Fe(CO)4Hg moiety which itself can be obtained by reaction of iron pentacarbonyl and mercuric sulphate. No structural information on these compounds is available, although Wells2 has suggested that Fe(CO)4Hg is polymeric and trans.

Raman and far-i.r. spectra for single crystals of tetrakis(thiourea)nickel(II) dichloride have been obtained at ca. 120 K and at ambient temperature. The results allow unambiguous assignment to A, B, and E species (in C4 symmetry). Descriptions of many of the internal modes are also offered.

The far-infrared spectra (70–400 cm.–1) of tellurium tetrachloride show that its structure in the solid state differs from that in benzene solution, in which a molecular form is most probable. The solid bromide has a similar structure to the chloride.

An outline is given of an Algol computer programme for normal co-ordinate analysis. Some improvements in the force-constant refinement process are reported. The spectra of diborane, and of six halides of the formula M2X6(M = Al, Ga, or ln), have been analysed. In each case the force field is built up from the SVFF by adding interaction terms one by one, only those that are determined by the data being accepted. Force fields for all of the M2X6 molecules can be constructed by choosing 10 or more force constants from a set of 13; the force field for diborane differs considerably from these. A B–B force constant of 2·511 mdynes/A was found for diborane. In contrast, calculations for the M2X6 molecules became unstable when an M–M force constant was included, contrary to a previous report. An error in our previous calculations on auric chloride is corrected.

Copper(II) halides form complexes of the type CuX2L2(L is 2,3-diphenyl- and 2-methyl-quinoxaline) and CuX2L (L is 2,3-dimethylquinoxaline) with substituted quinoxaline. The 2,3-diphenylquinoxaline complexes appear to be monomeric whereas the others are polymeric. The 2-methylquinoxaline complexes have halide bridges and the 2,3-dimethyquinoxaline complexes are square-planar with organic ligand bridges. These structures are deduced from reflectance and far-infrared spectra and an examination of molecular models. Some copper(II) nitrate complexes of these ligands are described.

Partial or complete Raman and i.r. spectra are reported for WOCl4, WOBr4, MoO2Cl2, MoO2Br2, and WO2Cl2 as solids. A full assignment is given for WOCl4, and possible structures for the dioxide dihalides are discussed. A normal-co-ordinate analysis of WOCl4 is made.

Raman spectra of hexamethylenetetramine and several substituted benzophenones have been studied in situ on thin layer chromatography plates. Success depends upon the nature of the substrate (Kieselgel HR was the best found), the eluant, the retention factor, fluorescence of both plate and sample, and the scattering efficiency of the sample itself. It is concluded that the method is viable within the restrictions discussed, but that an instrument with rapid spectrum accumulation facilities would be necessary for routine analytical application.

The complex Raman and i.r. spectra of ruthenocene at ambient and liquid-nitrogen temperatures have been interpreted with the aid of solution and Raman single-crystal data to yield a complete assignment, including inactive modes. The polarisation property of the π(C–H) modes in ferrocene has been determined for the first time. Contrary to the accepted order, the i.r.-active ring ‘tilt’ mode of ruthenocene comes at lower frequency than the M–ring bond stretch.

Raman spectra are reported for single crystals of the title compounds together with single-crystal i.r. reflectance data for the tetrakis-complex. The bis-complex is discussed on the basis of a factor-group analysis, but for the more complex unit cell of the tetrakis-complex a molecular model provides an adequate basis for assignment.

Single-crystal Raman spectra have enabled the identification and assignment to be made of nearly all the predicted factor-group fundamentals derived from internal modes of the anion in potassium chromate. Single-crystal i.r. and Raman methods were also used to study the lattice modes of this compound.

Nearly all the unit cell modes predicted by a factor-group analysis of tetrakis(thioacetamido)copper(I) chloride have been observed for single crystals in both Raman and i.r. spectra. The results show that the very simple i.r. spectrum of the Nujol mull is produced by the overlap of a large number of bands of different symmetry and similar frequency.

Infrared spectra have been obtained over the range 70–4000 cm.–1 for complexes of the types InX3L3 and InX3L2, where X = Cl, Br, and I and L = donor ligand. The evidence indicates a pentaco-ordinate monomeric structure for the InX3L2 series [L = Ph3PO, Ph3P, or ½(Ph2P·C2H4·PPh2)] in the solid state, the trans-octahedral form for InX3(dimethyl sulphoxide)3, and the cis-octahedral structure for InX3py3.

The observation of Raman and far-i.r. spectra of oriented single crystals of [Et4N]2[InCl5] has enabled a probable assignment to be given for the anion.