Infrared and Raman spectra of lithium trihorate: Vibrational assignments and a correlation with its nonlinear optical activity

Infrared and polarized single crystal Raman spectra of lithium triborate (LBO; LiB₃O₅) are reported and analysed. All four (A₁, A₂, B₁ and B₂) symmetry species of the C_2v, point group isomorphic to the C_2v⁹(Pna2₁) space group are Raman active in distinct crystal polarization experiments. A complete set of symmetry assignments based on a factor group analysis is presented. The internal and external vibrations are separated on the basis of frequency and the observation that the magnitude of the correlation splitting for the internal modes is very small. A comparison of the internal frequencies of various borate species suggests a correlation between the B-O stretching frequency and the nonlinear optical efficiency of the material.     

IR- and Raman-active normal vibrations of rare earth oxyfluorides,REOF; RE=Y,La, and Gd

The vibrational levels of selected rhombohedral rare earth oxyfluorides, REOF; RE = La, Gd, and Y, were deduced from the room temperature IR absorption and the Raman scattering spectra between 180 and 1000 cm⁻¹ and between 10 and 700 cm⁻¹, respectively. All four IR-active (2A_2u + 2E_u) and six Raman-active (3A_1g, + 3E_g) normal modes predicted by the group-theoretical analysis for the D_3d factor group were observed. The vibrations were assigned with the aid of their intensity and frequency in good agreement with the cubic fluorite-like structure of stoichiometric REOF.     

Komplexchemie Polyfunktioneller Liganden. XXXIII. IR-, FIR- und RAMAN-Spektroskopische Untersuchungen an Metalltricarbonylderivaten mit vierzähnigen P- und As-Liganden im Bereich 2000–150 cm−1

Complex Chemistry of Polyfunctional Ligands. XXXIII. IR, FIR and Raman-Spectroscopic Studies on Metaltricarbonyl Derivatives of Tetradendate P- and As-Ligands in the Region 2000–150 cm^?1 The IR- (2000–250 cm^?1), FIR- (350–150cm^?1) and RAMAN -spectra (2000–150 cm^?1) of the tetradendate ligands C[CH₂E(C₆H₅)₂]₄ (E = P, As) and of the complexes of the type cis-M(CO)₃(R₂ECH₂)₃C(CH₂ER₂) (M = Cr, Mo, W; E = P, As; R = C₆H₅) have been obtained. A comparison of the spectra of these compounds and consideration of previously reported data of analogous compounds allowed the assignment of all ligand vibrations. After localisation of the ligand vibrations an assignment of the v (CO) (A₁ + E), δ (MCO) (A₁ + 2E, v (MC) (A₁ + E) and v (ME) (A₁) modes was possible for the coordination polyhedra cis-M(CO)₃)E₃ (point group C_3v). The v(ME) (E) modes were unobserved by its very low frequency.     

Synthesis,characterization and vibrational investigation of divinylborinic anhydride

The new molecule divinylborinic anhydride [(CH₂CH)₂B]₂O as been prepared by the limited hydrolysis of divinylchloroborane. Characterization of the compound has included the preparation of 1 : 1 adducts with trimethylphosphine, dimethylphosphine and trimethylamine. Born-11 and carbon-13 NMR spectra have been obtained and have been interpreted in terms of mesomeric interactions between the empty boron pπ orbital and unshared pairs of electrons on oxygen as well as the pi electron system of the vinyl moiety. The Raman spectra (3500–200 cm^-1) of liquid and solid [(C₂H₃)₂B]₂O and the infrared spectra (3500–200 cm^-1) of gaseous and solid [(C₂H₃)₂B]₂O ¹ have been investigated for both the ¹⁶O and ¹⁸O isotopic species. The vibrational data indicate that the molecule possesses C₁ symmetry and a linear BOB angle.     

The ESR spectrum of the C5F5 radical

Experimental results of an investigation of the ESR spectrum of the pentafluorocyclopentadienyl radical C₅F₅ in various liquid and solid matrices are reported. At temperatures above 120 K the ESR spectra indicate a five-fold symmetry with a fluorine isotropic splitting of 16 G and an isotropic g tensor of 2.0041. From liquid solutions a value A_iso¹³C ≈ 2.1 G for the isotropic coupling of the ¹³C₁ species in natural abundance was found. The ESR spectra exhibit a pronounced temperature dependence, which is interpreted by lineshape analysis to originate from an anisotropic hyperfine interaction tensor of fluoroine, partially averaged by a uniaxial rotational reorientation. From ESR spectra of polycrystalline samples the principal value A6 = 57.5–58.3 G depending on the matrix was derived.     

Far IR and Raman spectra of some gaseous titanium,zirconium and hafnium cyclopentadienyl chlorides

The far IR and Raman spectra of gaseous (C₅H₅)TiCl₃ and (C₅H₅)₂MCl₂ species (M = Ti, Zr and Hf) are reported. The results are compared to the previous vibrational analysis of the corresponding species in the solid and matrix isolated phases. The assignment of the metal skeletal vibrations is reexamined in further detail on the basis of the new spectroscopic measurements. The torsional frequencies and the related potential barriers are investigated.     

Single crystal Raman study of potassium oxalate monohydrate,K2C2O4. H2O,and potassium oxalate monodeuterate,K2C2O4. D2O

Raman spectra of poly crystalline and single crystal K₂C₂O₄. H₂O and K₂C₂O₄. D₂O have been recorded at room temperature. From an earlier neutron diffraction study it is known that the space group is C⁶₂h. The water molecule occupies a C₂ site and the oxalate ion a C₁ site. The assigned water vibrations show small factor group splitting between g modes (Raman active) and u modes (IR active). The internal oxalate vibrations are found to have wavenumbers in good agreement with those reported from Raman studies of other oxalates.     

Fluorescence spectrum of the benzene radical cation in solid argon

Argon/benzene samples were condensed at 12 K with continuous argon resonance radiation. Laser excitation at 421 nm produced a weak emission with structure at 19770, 19140 and 18290 cm^?1, assigned to the ²A_2u → ²E_1g emission of C₆H₆⁺. Observation of 630 and 1480 cm^?1 intervals for the vibrations v₁₈ (e_2g) and v₆ (e_2g), respectively, supports this assignment.     

Synthesis and structural investigations of some alkylamine pentacyanoferrate(II) complexes

A series of alkylamine pentacyanoferrate(II) complexes, Na₃[Fe(CN)₅L]·(H₂O)_x, where L = (CH₃)₂NH, (C₂H₅)₂NH, (C₃H₇)₂NH, (C₄H₉)₂NH, (C₆H₅)₂NH, (C₂H₅)₃N, (C₄H₉)₃N or C₆H₁₁NH₂, were synthesized and characterized by analysis, magnetic, IR and Mössbauer spectroscopic studies. Characteristic CN and FeCN vibrational frequencies were found to be affected by the nature of the substituent. Mössbauer spectra exhibited a two-line quadrupole doublet with isomer shifts (δ) − 0.04 to 0.49 mm s⁻¹ (relative to sodium nitroprusside) and quadrupole splitting (ΔE_Q) of 0.73–1.92 mm s−1. A correlation of δ vs ΔE_Q has been attempted and the sign of the electric field gradient predicted. Bonding characteristics seem to change from simple mono- and dialkylamines to bulky di- and trialkylamines in pentacyanoferrate(II) complexes.     

Raman spectra of gases: XIV. Hexachlorodisiloxane

The Raman spectra (50–1200 cm^?1) of gaseous, liquid, and solid (Cl₃Si)₂O have been recorded. The infrared spectra of the gas and solid have been recorded from 55–2000 cm^?1 . The spectra of the gas have been interpreted in detail on the basis of C_2v symmetry with the A₁ skeletal Si-O-Si bend assigned at 63 cm^?1. The spectra gave evidence that there are structural changes upon condensation of the gas and the Si-O-Si angle approaches linearity in the solid state. The opening of this angle is probably due to crystal packing factors.     

Spectra and structure of gallium compounds: Part VII. Microwave,infrared and raman spectra and normal coordinate analysis of trimethylamine-trimethylgallane

The infrared (100–3500 cm^?1) and Raman (25–3200 cm^?1) spectra of the solid phases of (CH₃)₃NGa(CH₃)₃ and (CH₃)₃¹⁵NGa(CH₃)₃ have been recorded near liquid nitrogen temperatures as well as the Raman spectrum (100–3200 cm^?1) of the liquid phase at ~50°C and the low resolution microwave spectrum (26.5–39.0 GHz) of (CH₃)₃NGa(CH₃)₃. The spectra have been interpreted on the basis of C_3v molecular symmetry and a vibrational assignment is proposed for all but the torsional modes. The B value calculated from the microwave spectrum is consistent with published structural parameters reported from an electron diffraction study. A modified valence force field has been used to calculate the observed frequencies and the potential energy distribution. The force constants presented are consistent with changes in the structural parameters of the Lewis acid and base upon adduct formation. Extensive mixing has been observed among the low-frequency modes. The Ga-N stretching force constant (1.6 mdyn A^?1) has a value intermediate between those of (CH₃)₃NGaH₃ and H₃NGa(CH₃₃).The lack of apparent factor group splitting indicates that only one molecule occupies each primitive cell, situated on either a C₃ or C_3v site. A rhombohedral space group such as R3m(C⁵_3v) is consistent with these observations.     

Polarized infrared reflection spectra of AlCl3·6H2O single crystals

Polarized i.r. reflection spectra of AlCl₃·6H₂O single crystals are presented in the range 40–4000 cm⁻¹. The oscillator parameters and the transverse and longitudinal optical phonon frequencies are calculated by means of the classical oscillator fit method. The TO/LO splittings and frequency shifts of the water bands in A_2u and E_u species are discussed in terms of hydrogen bonds, the metal—water interaction and the orientation of the H₂O molecules in the lattice.     

Vibrational Spectra of the Cyclic SN-Compounds S4N4, S4N4H4 and S3N3Cl3

The IR and Raman spectra of solid and dissolved S₄N₄, S₄N₄H₄, S₄N₄D₄ and S₃N₃Cl₃ have been recorded and are assigned according to D_2d, C_4v and C_3v symmetry respectively. In the solid state, many forbidden bands and splittings of degenerate vibrations are observed because of the symmetry lowering in the crystals. Due to the different size and shape of the rings and to strong coupling of the normal modes there is no clear correlation between the SN ring stretching vibrations and the strength of the SN bonds, except for the one of the E modes. However, the stretching force constant show the trend expected from changes in interatomic distances.     

Solid state NMR spectroscopy of metal carbonyls. The influence of site symmetry on the solid state spectrum of cis-(η5-C5H5)2Fe2(CO)4

Solid state carbon-13 NMR spectra of metal carbonyls are readily obtained using commercial instrumentation. The observed isotropic chemical shifts are in good agreement with solution values. Furthermore there is a one-to-one correspondence between crystallographically unique carbonyls and magnetically distinguishable carbonyls in the absence of accidental degeneracies. For cis-(η⁵-C₅H₅)₂Fe₂(CO)₄ the site symmetry is C₁ while the molecular symmetry is C_2ν. The lower solid state symmetry gives rise to more resonances in the solid spectrum than in solution. Magic angle tuning and chemical shifts were obtained using hexamethylbenzene as a standard.     

Electronic structures of organometallic complexes of f elements LXXVII: Complementary information of polarized Raman spectra of oriented single crystals and model calculations on the basis of density functional theory for assigning the vibrational spectra of decamethylferrocene

The far and mid infrared (FIR/MIR) spectra of powdered Fe(η⁵-C₅Me₅)₂ (FeCp1₂) as well as the polarized Raman spectra of an oriented single crystal (where the four FeCp1₂ molecules of D_5d symmetry in the unit cell are pairwise perpendicular to each other) have been recorded. The polarization selection rules were developed for this situation which allow the assignment of the observed Raman lines to irreducible representations (irreps) which agree well with the predictions of a calculation applying density functional theory. This finding suggests additional correlations to the observed (unpolarized) bands in the FIR/MIR spectra with the calculated wavenumbers (and their irreps) of IR active normal modes. Neglecting the νCH vibrations, a r.m.s. deviation of 7.0 cm^?1 for 41 assignments (IR and Raman) could be achieved. The frequencies of the calculated νCH vibrations, however, are on the average 55 cm^?1 higher than the experimental ones. Skeletal and intra-ligand vibrations could be separated and all previous assignments of the former had to be revised. Because of mixing, the graphical representations of the two skeletal modes of E_1u symmetry do not resemble the idealized ones of a typical sandwich complex but those of FeCp₂ shown in the literature. In-phase and out-of-phase intra-ligand motions of the Fe[(C₅C₅)]₂ moiety have calculated wavenumber differences between 3 and 42 cm^?1. Additionally, because of mixing with skeletal modes some of the low frequency intra-ligand vibrations display a noticeable dependence on the mass of the central atom which prevents the direct transfer of the identified βCCH₃ and γCCH₃ normal modes from MCp1₂ (M = Fe, Ru) to LnCp1₃ (Ln = La, Ce, Pr, Nd, Sm) complexes.     

Stretching vibrations of CH bonds in spectra of dicarbaclosododecaboranes (p-, m-, and o-carboranes)

Parameters of bands corresponding to stretching vibrations of C-H bonds in spectra of o-, m-, and p-isomers of the icosahedral carborane B₁₀H₁₀C₂H₂ have been measured with high accuracy. The stretching vibrations of C-H bonds in spectra of o- and m-carborane (12), molecules which have C_2v point group symmetry, are demonstrated to appear the same as in the spectrum of the p-isomer with D_5d symmetry. The frequencies of Raman and IR lines practically coincide. This indicates the absence of interaction of the stretching vibrations of the two C-H bonds even in the o-carborane molecule.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2263–2267, October, 1989.     

Synthesis and structure of pseudotetrahedral Co(II) zwitterionic complexes: trichloro(1-methylpiperazin-1-ium-N4)cobalt(II) and trichloro(1,4-dimethylpiperazin-1-ium-N4)cobalt(II)

The pseudotetrahedral cobalt(II) zwitterionic complexes, [CoCl₃(H₂Meppz)] (1) [H₂Meppz⁺=1-methylpiperazin-1-ium cation] and [CoCl₃(HMe₂ppz)] (2), [HMe₂ppz⁺=1,4-dimethylpiperazin-1-ium cation] have been synthesized and characterized in the solid state by X-ray single crystal analysis, IR spectra, magnetic measurements and electronic spectra. In both the compounds the cobalt(II) center is coordinated in a distorted tetrahedral fashion by the three chloride ions and by one nitrogen of the piperazine ring that retains the more stable chair conformation. The distorted coordination polyhedron in complex 1 preserves the C_3v symmetry while in complex 2 it retains only the m symmetry. In complex 1, the (H₂Meppz)⁺ cation binds the Co(II) ion in the equatorial position of the piperazine ring using the unmethylated N1–H nitrogen atom that is less hindered than the methylated one. Complex 2, on the contrary, is a novelty being the first example of a Co(II) ion bound in the axial position of a piperazine ring, this produces a long Co(II)–N bond, 2.108(4) Å. Electronic spectra in the solid state are in perfect accordance with the X-ray crystallographic results indicating a C_3v symmetry for complex 1 and a C_s(m) symmetry for complex 2. These complexes present strong two-center and three-center hydrogen bonds of N⁺–H⋯Cl type.     

Die schwingungsspektren der tetra-cyclopropyl-verbindungen von silicium,germanium und zinn

The IR and Raman spectra of Si(C₃H₅)₄, Ge(C₃H₅)₄ and Sn(C₃H₅)₄ were recorded and assigned on the basis of D_2d symmetry, which, however, is strictly realised only for the tin compound. The assignments are in accordance with the dipole moments (1.8, 3.4, 2.0 Debye, respectively).     

Study of the contact charge transfer behavior between cryptophanes (A and E) and fullerene by absorption, fluorescence and H NMR spectroscopy

A group of novel cage-like compounds cryptophanes A and E were synthesized from vanillin by a three-step method. The intermolecular interaction between cryptophanes (A and E) and fullerene (C₆₀) was investigated in detail by absorption, fluorescence and ¹H NMR spectroscopy. The absorption of C₆₀ at 410-650 nm decreased in the presence of cryptophanes A or E. The decrease in absorption intensity was proportional to the concentration of cryptophanes A or E. On the other hand, the fluorescence intensity of cryptophanes A or E decreased and the emission maxima were blue-shifted with the increase in C₆₀ concentration. These results suggest that contact charge transfer (CCT) complexes can be formed from C₆₀ with cryptophanes A or E. In addition, the electrochemical behavior of cryptophanes (A and E) and C₆₀ was studied by cyclic voltammetry. The redox currents of cryptophanes (A and E) decreased and the peak potentials were shifted on addition of C₆₀. The changes in the chemical shifts (Δδ) of aromatic protons of cryptophanes (A and E) in their NMR spectra further support that CCT complexes were formed with cryptophanes as the electron donors and C₆₀ as the electron acceptor.     

Inelastic neutron scattering study of low frequency motions in [Co(C5H5)2+] and [Cr(C6 H62+] intercalated in the MnPS3 layered compound

The incoherent inelastic neutron scattering (INS) spectra of Mn_0.84PS₃[Co(C₅H₅)₂] _0.32 and Mn_0.86 PS₃[Cr(C₆H₆)₂]_0.28 compounds at 10 K have been investigated within the frequency ranges 0–80 cm^?1 (E₀ = 12.5 meV) and 0–360 cm^?1 (E₀ = 50 meV). Also, infrared and Raman spectra (0–400 cm^?1 of Cr(C₆H₆)₂I at various temperatures have been obtained for the first time. From a comparison of far infrared, low frequency Raman and INS results, we propose an assignment for the internal torsion and for the librational motions in the intercalated organometallic cations. An estimate of the potential barrier height against the torsion and the R′_z whole-body rotation is derived; these values are compared with those calculated for the corresponding iodide salts. We conclude that a significant decrease of the intermolecular forces acting on the rings is taking place within the interlamellar space.