Raman spectrum and structure of solid P2Cl4

The Raman spectrum of liquid and solid polycrystalline P₂Cl₄ has been recorded from 30 to 700 cm^–1. The far infrared spectrum of the solid has also been reinvestigated. From these data, it is necessary to reassign the P-P stretch (a _g), the PC1₂ rock (a _u) and the PCl wag (b _u). Three lattice modes were observed in the Raman spectrum whereas none was found in the infrared spectrum. No correlation field splitting was observed for any of the intramolecular fundamentals. Although the vibrational data for the crystalline state is best interpreted in terms of atrans (C _2h, 2/_m) conformation, there is some evidence that another form may be present, in small amounts, in the fluid states. Furthermore, no evidence for the torsional mode, previously assigned at 91 cm^–1, has been found and calculations have been made which indicate that such a frequency would lead to an un-acceptably high barrier to internal rotation of the asymmetric PC1₂ rotor.Taken from the thesis of J. E. Saunders which has been submitted in partial fulfillment of the Ph.D. degree.     

Spectra and structure of organophosphorus compounds,XVIII: Infrared and Raman spectra of [(CH3)2PS]2, [(CD3)2PS]2, and [(CH3CH2)2PS]2 in the solid state

The infrared (80–3500 cm^–1) and Raman (10–3500 cm^–1) spectra of solid [(CH₃)₂PS]₂, [(CD₃)₂PS]₂, and [(CH₃CH₂)₂PS]₂ have been recorded. A complete vibrational assignment is proposed for tetramethyldiphosphine disulfide on the basis ofC _2h molecular symmetry. The observed intermolecular vibrations indicate little factor group effects, and no frequency differences were observed for the normal modes of the two different molecules which exist in the crystal as reported from the x-ray study. Most of the observed bands in the spectrum of tetraethyldiphosphine disulfide have been assigned. At least two of the three optical librational modes were observed in the Raman effect.     

Raman spectrum of solid glyoxal

The Raman spectrum of solid glyoxal has been recorded from 100 to 3500 cm^–1. Fundamental frequencies were observed at 2882, 1729, 1364, 1078, 1050, and 551 cm^–1 and assigned as the C—H stretching, C=O stretching, C—H in-plane bending, C—C stretching, C—H out-of-plane bending and COH rocking modes, respectively. The infrared spectrum of the solid has been investigated from 33 to 4000 cm^–1, and the values observed for the fundamentals are compared with those previously reported from studies of the vapor. The unusual frequency shifts upon solidification are discussed. A comparison of the infrared and Raman bands in the crystal shows that the mutual exclusion principle is operative. It is concluded from this alternate forbiddance that the molecule has a centrosymmetric structure in the crystal and that each molecule occupies a C _i (¯1) site. The factor group of the crystal is believed to be eitherC _2h (2/m) orD _2h (mmm) with two or four molecules per primitive unit cell.We thank the National Aeronautics and Space Administration for supporting this research by Grant NGR-41-002-003.     

Infrared and Raman spectra of potassium pentacyanonitrosylmanganate(I) dihydrate: K3[Mn(CN)5NO]· 2H2O

The infrared spectra of polycrystalline K₃[Mn(CN)₅NO]·2H₂O at different degrees of deuteration were recorded between 4000 and 200 cm^–1, both at room and low temperature. The room-temperature Raman spectrum of the isotopically normal powder was also obtained. The observed bands were assigned to the internal vibrational modes of the [Mn(CN)₅NO]^–3 ion and to the internal and librational modes of water of hydration. In accordance with X-ray diffraction studies, the spectra showed the existence of two crystallographically distinct types of water molecules located in different sets of sites ofC ₁ symmetry.A communication on this subject was presented at the XVI Latin American Chemistry Congress, Rio de Janeiro, Brazil, October 14–20, 1984.     

Spectra and structure of phosphorus-boron compounds,XII1 Vibrational spectra and molecular symmetry of tetramethylbiphosphine-bisborane

The infrared (200–3500 cm^–1) and Raman (50–3500 cm^–1) spectra of two isotopic species of tetramethylbiphosphine-bisborane, (CH₃)₄P₂·2BH₃ and (CH₃)₄P₂·2BD₃, in the solid state at low temperatures have been recorded. The spectra have been interpreted in detail on the basis ofC _2h molecular symmetry. The P-B stretching modes were assigned to bands at 599 and 567 cm^–1 in the Raman and infrared spectra of the light compound, respectively. Only one P-P stretching mode was observed in the Raman spectra. The vibrational data appear to be consistent with the presence of only one conformer in the solid state, which is at variance with the conclusions from an X-ray study. Considerable splitting of the low-frequency bending modes was observed for both compounds; this splitting has been attributed to the factor group.For part XI, see J. D. Odom, V. F. Kalaskinsky, and J. R. Durig,Inorg. Chem. 14, 2837 (1975).Taken in part from the thesis of R. W. MacNamee which was submitted to the Department of Chemistry in partial fulfillment of the Ph.D. degree (1974).     

Raman spectrum of vitreous As2S3

The spontaneous Stokes and anti-Stokes Raman spectrum of vitreous As₂S₃ is reported. The spectrum was recorded with both HeNe and Ar ion laser excitation lines in the transmission and reflection modes respectively. Spectra were recorded at various temperatures between 20°K and 465°K, the softening temperature of As₂S₃ glass. It is shown conclusively that the quasicontinous scattering observed at low wave number shifts (< 100 cm⁻¹) is real in agreement with the theory of Shuker and Gammon and not an arbitrary background as previously reported. An approximate density of vibrational states is deduced from the polarized Raman spectra.     

Vibrational spectra oftrans-dichlorodiiodoethylene

The infrared spectra oftrans-dichlorodiiodoethylene as a solid and in solution were recorded in the region 4000–25 cm^–1. Raman spectra of the compound were obtained and semiquantitative polarization data were calculated.The mutual exclusion between the infrared and Raman frequencies are in agreement with the expectedC _2h (2/m) symmetry for this molecule. The fundamentals have been assigned and a normal coordinate analysis carried out. Thermodynamic functions and the root mean square amplitudes of vibration have been obtained.The authors wish to acknowledge financial support from theNorwegian Research Council for Science and the Humanities.     

Absorption spectrum of Ni2+ doped in NH4Br single crystal

The optical absorption spectrum of Ni²⁺ doped in NH₄Br single crystals has been studied at room and liquid-air temperatures. The observed ambient bands at 6300, 11,600, 13,400, 18,500, and 20,000 cm^–1 have been assigned, respectively, to the transitions³ A ₂(F) ³ T ₂(F),³ T ₁(F),¹ E(D),¹ T ₂(D and³ T ₁(P). The crystal field parameters evaluated areD _q=630 cm^–1,B=850 cm^–1, andC=3600 cm^–1. In assigning the location of Ni²⁺ ions within the lattice, evaluations are made of the (limited) extant comparable data. It is then concluded that Ni²⁺ enters an octahedral interstitial, rather than a substitutional, site. It is surrounded by four bromide ions, in a plane, with two polarized water molecules at the opposing fifth and sixth positions.     

Vibrational spectra and structure of organophosphorus compounds

The infrared spectra of both CH₃OPSClF and CD₃OPSClF in the vapor phase have been recorded from 4000 to 33 cm^–1. The Raman spectra of the liquids have been recorded and a temperature study of the CD₃OPSClF spectrum has been completed. Two isomeric configurations are indicated from the low-temperature Raman spectra. The doublet due to the P=S stretching vibration has a separation of only 15 cm^–1. From the variation in the relative intensity of the doublet, an energy difference of –450 cal/mol was obtained for the two isomers. The fundamental vibrations are assigned on the basis of the band positions and isotopic shift factors. The assignments are compared to those previously given for the CH₃OPSCl₂ and CH₃OPSF₂ molecules.For part VIII,see Inorg. Chem.8, 2796 (1969).Taken in part from the thesis submitted by J. W. Clark to the Department of Chemistry for the Ph.D. degree, August 1968.We wish to thank Miss Ann Perez for recording the infrared spectra. Acknowledgement is also made to the United States Army Research Office, Durham, for the support of this research by Grant Number DA-ARO-D-31-124-G824.     

Incorporation of H2 in vitreous silica, qualitative and quantitative determination from Raman and infrared spectroscopy

Incorporation mechanisms of H₂ in silica glass were studied with Raman and infrared (IR) microspectroscopy. Hydrogenated samples were prepared at temperatures between 800°C and 955°C at 2 kbar total pressure. Hydrogen fugacities (f_H2) were controlled using the double capsule technique with the iron–wüstite (IW) buffer assemblage generating f_H2 of 1290–1370 bars corresponding to H₂ partial pressures (P_H2) of 960–975 bars. We found that silica glass hydrogenated under such conditions contains molecular hydrogen (H₂) in addition to SiH and SiOH groups. H₂ molecules dissolved in the quenched glasses introduce a band at 4136 cm⁻¹ in the Raman spectra which in comparison to that of gaseous H₂ is wider and is shifted to lower frequency. IR spectra of hydrogenated samples contain a band at 4138 cm⁻¹ which we assign to the stretching vibration of H₂ molecules located in non-centrosymmetric sites. The Raman and IR spectra indicate that the dissolved H₂ molecules interact with the silicate network. We suggest that the H₂ band is the envelope of at least three components due to the occupation of at least three different interstitial sites by H₂ molecules. Both, Raman and IR spectra of hydrogenated glasses contain bands at 2255 cm⁻¹ which may be due to the vibration of SiH groups. Under the assumption that the reaction Si–O–Si + H₂ → Si–H + Si–O–H describes adequately the ‘chemical dissolution' of H₂ molecules, the SiH concentrations in our samples were determined and the molar extinction coefficient for the SiH absorption band in the infrared (₂₂₅₅(SiH)) could then be estimated to be 45 ± 3 l/mol cm. The solubility of molecular H₂ in our hydrogenated samples was determined using the IR absorption band at 4138 cm⁻¹ and the extinction coefficient given by Shelby [J. Non-Cryst. Solids 179 (1994) 138]. Samples quenched with different cooling rates gave nearly identical Raman and IR spectra, suggesting that the chemical dissolution of hydrogen (SiH and SiOH) can be quenched to room temperature without changing relative concentrations and that no exsolution of hydrogen occurred during the quench.     

Raman,infrared, and optical spectra of some silver(I) sulfamides

Raman and infrared spectra of disilver sulfamide, Ag₂(HNSO₂NH), and tetrasilver sulfamide, Ag₄(NSO₂N), together with their¹⁵N and²H derivatives (at 300 and 80 K), are reported and interpreted. Resonance conditions for the Raman spectrum of the deep red tetrasilver sulfamide is assumed, but no overtone progression of any band is observed. Silver-nitrogen stretching bands appear in the frequency region 300–200 cm^–1. Although the X-ray crystal structures of the compounds reveal short AgAg distances, no frequency assignable to metalmetal stretching vibrations could be clearly located except for Ag₄(NSO₂N) in the case of the strong band at 288 cm^–1 appearing in the infrared only. This band is assigned to a lattice vibration having high frequency due to strong metalmetal interaction. Optical diffuse reflectance and fluorescence emission/excitation spectra are included and compared to the literature data for silver-exchanged zerolites.     

Synthesis and crystal structure of 1-acetyl-3-bromo-3-phenylazetidine and 1-phenyl-2-(N-acetyl-N-formyl)-aminoethanone

1-Acetyl-3-bromo-3-phenylazetidine (1), C₁₁H₁₂BrNO, has been synthesized and characterized by spectroscopic methods and single crystal X-ray analysis. It crystallizes in the space group P2 ₁/c with a = 8.633(1), b = 7.461(1), c = 17.204(1) Å, = 98.403(7)°, V = 1096.2(2) ų, Z = 4, D _calc = 1.540 g cm^–3. The azetidine ring is nearly planar since the four atoms are within ±0.039(5) Å of the mean square plane calculated for the heterocycle. The attempt to obtain a highly strained 2-azetine derivative from the above compound gave, surprisingly, 1-phenyl-2-(N-acetyl-N-formyl)-aminoethanone (2), C₁₁H₁₁NO₃. This compound has been also characterized by spectroscopic methods and single crystal X-ray analysis. It crystallizes in the space group P2₁2₁2₁, with a = 5.4719(3), b = 8.3205(6), c = 23.298(3) Å, V = 1060.7(2) ų, Z = 4, D _calc = 1.286 g cm^–3. The aminoethanone residue is in a near planar conformation where the torsion angles are 7(2)° for N–C–C–=O and –173(2)° for N–C–C–C(Ph).     

Glass formation in the MoO3–Nd2O3–La2O3–B2O3 system

In MoO₃–Nd₂O₃–B₂O₃ and MoO₃–Nd₂O₃–La₂O₃–B₂O₃ systems, glasses were obtained in the region between 20 and 30 mol% Ln₂O₃. A liquid-phase separation region was observed near the MoO₃–B₂O₃ side up to 20 mol% Ln₂O₃ (La, Nd). The amorphous phases were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), UV–VIS and infrared spectroscopy (IR). According to DTA data B₂O₃-rich glasses are stable up to 630 °C while glasses rich in MoO₃ are stable up to 430 °C. The glasses are transparent in the visible region. Structural models for the glasses network were suggested on the basis of IR spectral investigations. It was established that BO₃ (1380 cm⁻¹), BO₄ (1100–950 cm⁻¹) and MoO₄ (860 cm⁻¹) groups build up the glass network. MoO₆ units (band at 880 cm⁻¹) together with BO₃ units participate in the formation of the glass network with a high MoO₃ content (80–90 mol%).     

Low frequency Raman scattering in chalcogenide glasses

Low frequency Raman spectra of chalcogenide glasses are analyzed in terms of matrix element effects and modes of a layered structure. The spectra of GeSe₂ at low temperature shows no peaks which can be assigned to layer modes. The reduced spectra indicates that the density of states exhibits nearly ω² dependence for ω < 60 cm^?1, and the coupling constant approaches ω² dependence at frequencies less than 20 cm^?1.     

Crystallographic and conformational analysis of 2-methyl-3-(2-nitro-phenyl)-4-phenyl-[1,2,4]oxadiazolidin-5-one

Molecular and crystal structure of 2-methyl-3-(2-nitro-phenyl)-4-phenyl-[1,2,4]oxadiazolidin-5-one, C₁₅H₁₃N₃O₄, have been determined by single crystal X-ray diffraction study. The title compound is monoclinic, with a = 10.0313(8) Å, b = 9.0372(5) Å, c = 15.5964(14) Å, β = 96.926(7)^∘, Z = 4, D_x = 1.42 g/cm³, μ (Mo-K_α) = 0.105 mm⁻¹, and space group is P 2₁/c. The structure was solved by direct methods and refined to a final R = 0.036 for 1894 reflections with I > 4σ (I). The crystal structure is stabilized by C–H⋅sO type inter-molecular, C–H⋅sN and C–H⋅sO type intra-molecular, π–π stacking and edge to face (C–H⋅s π-ring) interactions. To enlighten conformational flexibility of the title molecule, selected two torsion angles are varied from −180^∘ to +180^∘ in every 10^∘ separetely and then molecular energy profile is calculated and construed.     

Absorption spectrum of octahedral CoCl4(H2O)2 units in [(CH3)3NH]CoCl3·2H2O single crystal

The optical absorption spectrum of the octahedral moiety CoCl₄(H₂O)₂ in single crystal [(CH₃)₃NH]CoCl₃·2H₂O has been studied at room and liquidair temperatures. The observed ambient bands at 6800, 16,300, and 19,000 cm^–1 have been assigned, respectively, to the transitions⁴ T ₁(F) ⁴ T ₂(F),⁴ A ₂(F), and⁴ T ₁ (P). The crystal field parameters evaluated areD _q =B=850 cm^–1, andC=4.63B. At liquid-air temperatures the⁴ T ₁(P) band is seen to split into the expected four components ₇, ₈, ₈, and ₆, due to spin-orbit coupling, and the coupling coefficient was computed to be 525 cm^–1.     

Crystal and molecular structure of triphenyl[2-(p-tolylthio)ethyl]tin

The crystal and molecular structure of Ph₃SnCH₂CH₂SC₆H₄Me-p has been determined by X-ray crystallography. In each of the two independent molecules in the asymmetric unit the tin atom has an irregular tetrahedral geometry, with C–Sn–C valency angles ranging from 104.1(5) to 114.7(5)° in molecule (1) and from 104.6 to 112.7(6)° in molecule (2). The bond lengths, C_alkyl–Sn are 2.18(1) and 2.17(2)Å (in molecules (1) and (2), respectively) while the C_aryl–Sn bond lengths range from 2.11(1) to 2.13(1)Å in molecule (1) and from 2.09(1) to 2.14(1)Å in molecule (2). The Sn–C–C–S torsion angle, 172(1)° is the same for both molecules. NMR spectral data are presented; the¹H NMR spectrum in solution of the central-CH₂–CH₂-unit suggests that each of the protons on each of the CH₂ groups is magnetically distinct and that rotations about the C–C bond are slow on the NMR time scale. Comparisons with similar molecules are made and conformations discussed in terms of steric effects.     

The structure of dimethylcrocetin

The structure of dimethylcrocetin (DMCRT), prepared by alkaline hydrolysis in methanol of the glucosidic carotenoids extracted from the stigmata of theCrocus sativus L. flowers, has been determined. The molecule has the all-trans configuration and is planar forming a long conjugated system. The C–O bond length values of the two ester groups are shortened as expected. The compound (C₁₁H₁₄O₂)₂ crystallizes in the orthorhombic space group Pbcn witha=12.5907(7),b=7.5639(5) andc=21.963(2)Å. Dimethylcrocetin has characteristic Infrared absorptions at 1697 cm^–1 (C=O) and 1229 cm^–1 (C–O) and characteristic Raman vibrational modes at 1542 cm^–1 (C=C) and 1166 cm^–1 (C–C).     

Crystal and molecular structure of 2,2′-diphenyl-4,4′-di(2-phenyl-2-propenyl)-4, 4′-bi-5(4H)thiazolone

Molecules of C₃₆H₂₈N₂O₂S₂ crystallize in the monoclinic space groupP2₁/c with cell dimensionsa = 8.9326(3),b = 20.0197(11),c = 17.0349(8) Å, and = 92.20(1) °,Z = 4,D _x = 1.276 g cm^–3, (CuK) = 18.16 cm^–1. The structure was solved by Patterson methods and refined by least-squares calculations to anR of 0.057 andR _w = 0.066 for all reflections. The main differences in the two halves of the dimer are due to the different torsion angles in the propenyl chain.     

Crystal structure of Pt(S2COEt)2

The crystals of Pt(S₂COEt)₂ are orthorhombic, Pbca, with (at 20°C)a=7.799(3),b=7.368(6),c=20.588(7) Å.D _cale=2.46g cm^–3 forZ=4. The platinum atom resides on a crystallographic center of inversion and is bound to the four sulfur atoms of the xanthato ligand in a square planar geometry. The Pt–S distances are 2.313(6) and 2.320(7)Å with an intraligand S–Pt–S angle of 75.1(2)°.