Fourier Transform Infrared and Raman Spectra of Metal Halide Complexes of 3,5-Lutedine in Relation to Their Structures

Abstract

Fourier transform infrared (4000-200 cm¹) and Raman (3500-50 cm^?1) spectra are reported for metal(II) halide 3,5-lutidine (3,5-dimethylpyridine) complexes of the following stoichiometries: M(3,5L)₄X₂ M=Co or Ni, X=C1 or Br; M=Mn or Cu, X=Br; M=Cd, X=I; M(3,5L)₃X₂ M=Fe, X=C1; M=Cu, X=Br; Hg(3,5L) X₂ X=C1 or Br.

Vibrational assignments are given for all the observed bands. Some structure- spectra correlations are found. For a given series of isomorphous complexes the sum of the difference between the liquid and ligand values of the vibrational modes of 3,5-lutidine is found to increase in the order of the second ionization potentials of the metals. The frequency shifts are also found to depend on the halogen.     

The Infrared and Raman Spectra of 4-Phenylpyridine and Its Hofmann Type Complexes.

Abstract

The Infrared and Raman spectra of 4-Phenylpyridine are reported for the first time in the 4000-400cm^?1 range. Vibrational assignments have been made for fundamental modes on the basis of frequency shifts of coordinated legend, infrared and Raman band contours and comparisons with the assignments for related molecules. The infrared spectra of M (4-Phenylpyridine) Ni(CN)₄ complexes (M=Mn, Ni or Cd) are reported. Their structure consists of polymeric layers of [M-Ni(CN)₄]_∞ with the 4-phenylpyridine molecules bound to metal (M), similar to the structure found in Hoffmann type host complexes.     

Vibrational Spectroscopic Studies on the Dicyclopropylaminecadmium(II)Tetracyanometallate(II) Benzene Clathrates

ABSTRACT

New Hofmann–T_d-type clathrates of the forms Cd(CPA)₂M(CN)₄.C₆H₆ (CPA = cyclopropylamine; M?Cd or Hg) prepared in powder form and characterized by FT-IR, FT-Raman, far-IR spectra, X-ray diffraction, and elemental analyses are reported. Vibrational assignments are proposed for the bands of the host lattice and guest molecule. It is shown that the spectra are consistent with a proposed crystal structure for the compounds derived from X-ray diffraction measurements. The C, H, and N analyses were carried out for all the compounds. All the vibrational modes of coordinated CPA are characterized. The spectral features suggest that these compounds are similar in structure to the Hofmann–T_d-type clathrates.     

Vibrational investigation of 1-cyclopentylpiperazine: A combined experimental and theoretical study

FT-IR and Raman spectra of 1-cyclopentylpiperazine(1cppp)have been experimentally examined in the region of 4000–200cm-1.The optimized geometric parameters,conformational equilibria,normal mode frequencies and corresponding vibrational assignments of 1cppp(C9H18N2)are theoretically examined by means of B3LYP hybrid density functional theory(DFT)method together with 6-31++G(d,p)basis set.On the basis of potential energy distribution(PED)reliable vibrational assignments have been made and the thermodynamics functions,highest occupied and lowest unoccupied molecular orbitals(HOMO and LUMO)of 1cppp have been predicted.Calculations are employed for four different conformations in C1 and Cs point groups of 1cppp in gas phase.Comparison between the experimental and theoretical results indicates that B3LYP method is able to provide satisfactory results for predicting vibrational frequencies and the structural parameters,vibrational frequencies and assignments.Furthermore,C1(equatorial-axial)point group has been found as the most stable conformer of 1cppp.     

Temperature dependent study of the single crystal electronic spectrum of octahedral Ni2+ ion subjected to distortions in weak fields

Electronic spectra of two high spind ⁸ nickel complexes, Ni(en)₃Cl₂.2H₂O and Ni(OAc)₂.4H₂O, are reported. Polarized spectra were measured at 298 K. Temperature dependent spectra were measured using unpolarized light down to 20 K. The spectra at 20 K are well resolved revealing the features of spin-forbidden transitions and vibrational fine structure on some of the bands. Some of the spectra are deconvoluted to separate out the overlapping bands. The assignments are made usingD ₃ symmetry for Ni(en)₃Cl₂.2H₂O complex whileD ₄ symmetry is used for Ni(OAc)₂.4H₂O. The energies of the spectroscopic states are calculated and compared with the observed transition energies. The distortion parameters are determined.     

An Infrared Spectroscopic Study of Crystalline Copper (II) Propionate and Butyrate

Abstract

Abstract: The vibrational spectra of crystalline anhydrous copper (II) propionate and butyrate were studied by FT-IR spectroscopy. A detailed assignment of the spectra of both compounds is presented and discussed. It is shown that the presence of two non-equivalent sets of carboxylate ligands within the crystals gives rise to several band splittings, which are particularly evident in those bands ascribable to normal modes involving predominantly the -C_βH₃ or -C_βH₂-fragments. In addition, the vibrational assignments made for the studied molecules are shown to be very useful to help understanding the much more complex spectra of long chain copper carboxylates.     

Experimental vibrational spectra (Raman,infrared) and DFT calculations on monomeric and dimeric structures of 2‐ and 6‐bromonicotinic acid

In this work, the Fourier transform infrared and Raman spectra of 2‐bromonicotinic acid and 6‐bromonicotinic acid (abbreviated as 2‐BrNA and 6‐BrNA, C₆H₄BrNO₂) have been recorded in the region 4000–400 and 3500–50 cm⁻¹. The optimum molecular geometry, normal mode wavenumbers, infrared intensities and Raman scattering activities, corresponding vibrational assignments and intermolecular hydrogen bonds were investigated with the help of B3LYP density functional theory (DFT) method using 6‐311++G(d,p) basis set. Reliable vibrational assignments were made on the basis of total energy distribution (TED) calculated with scaled quantum mechanical (SQM) method. From the calculations, the molecules are predicted to exist predominantly as the C1 conformer. Copyright © 2009 John Wiley & Sons, Ltd.     

Far Infrared and Raman Spectra of Some Crystalline Iodomercurate Complexes

Abstract

Vibrational spectra of crystalline powders of [Nien₂] [HgI₃]₂ and [Men₂] [HgI₄] (where en = ethylene-diamine chelated to M = Ni(II), Pd(II) or Pt(II)) have been measured at room and liquid-nitrogen temperatures. The bands observed in the low frequency region 200–10 cm^?1 are interpreted in terms of mainly internal vibrations of the anions and external lattice modes. Raman and far infrared spectra are compared in order to make structural deductions. In comparison with present knowledge of the stereochemistry and vibrational spectroscopy of other iodomercurates, the triiodo-mercurate salt seems to contain nearly planar trigonal anions, while the tetraiodomercurates contain discrete tetrahedra. Probable site symmetries of the anions which may explain the spectra are discussed.     

Infrared Spectra of Some Metal (II) Complexes of 2-Aminomethylpyridine

Abstract

Band assignments in the IR spectra (700–150 cm^?1) of [M(amp)₃] (ClO₄)₂ (amp = 2-aminomethylpyridine; M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II), [Zn(amp)₂Cl₂] and [Pt(amp)Cl₂] derived from amp-ND₂, their unlabelled analogues, [Zn(amp)₂X₂] (X = Br, I) and [Pt(amp)Br₂] are discussed.     

The Vibrational Spectra of 9-Fluorenone and Some of Its Isotopic Isomers

Abstract

Vibrational spectra of 9-Fluorenone, 9-Fluorenone-¹⁸O and 9-Fluorenone-d₈ have been recorded in the solid state and solutions in the infrared and (4000–100 cm^?1) and in the Raman (4000–50 cm^?1). Differential infrared linear dichroic spectra have also been measured. The assignment of the vibrational bands is performed using the group vibrational concept, isotopic shifts and polarization features of the normal modes.     

Computer Resolution and Franck-Condon Analysis of the Electronic Absorption Spectrum of KMnO4 in Water

Abstract

The electronic absorptíon spectrum of KMnO₄ in water solution was analyzed. The spectral contour was resolved into component bands and then Franck-Condon approach was applied. In the investigated range of 13000–48000 cm^?1 a presence of three structureless and of two vibronic strong bands was stated. The change in the Mn-O equilibrium bond length was found to be 10.5pm for 2e·1t₁ transition (vibronic band about 18000cm^?1) and to be 16pm for the 2e·3t₂ transition (vibronic band about. 30000cm_?1). The appropriate wavenumber of the vibrational mode in these excited electronic states was found to be 735cm^?1 and about 780cm^?1, respectively. The ground electronic state wavenumber of the totally symmetric vibrational mode was fitted to be equal to 828cm^?1. Details of the proposed method of computer elaboration of electronic spectra with vibrational structure were discussed.

Electronic absorption spectra of some inorganic comppunds consist of a number of strongly overlapped bands due to their vibronic structure.^1–5 A detailed analysis of spectral contours of such compounds provides some useful information about their structure in both ground excited electronic states.

The electronic spectrum of permanganate ion is the typical example of vibronic spectra.¹ The main part of the past works based on the analysis of permanganate ion spectra in low temperatures and different polarizations. In such conditions the vibronic structure is rather good resolved and can be effectively studies.^1,3,6 Spectra of solutions as a rule are relatively poor resolved so their analysis has to be more sophisticated.

The main purpose of this work is a presentation of a new computer method for an effective study of vibronic spectra of solutions. This method has been applied to the electronic absorption spectrum of KMnO₄ in water. The method allowed us to fit the geometric parameters of spectral contour, to establish the origins and parameters of two progressions in the UV/VIS range as well as to calculate the changes in the Mn-0 equilibrium bond lengths and vibrational energy resulting from the electronic excitations of the soluted permanganate ion.     

Infrared Spectrum of Dihydridobis(ethylenediamine) Osmium Tetrachloro Zincate

The ethylenediamine trmsition metal complexes^1-9 of the type M(en)₂X₂ (M = Co, Ni, Cu, Pd, Pt and × = I, Br, C1, NO³, C10⁴) have infrared spectra of complicated nature which have been used for the study of conformation of the chelate ring. In dihydrldobis ZnC14 ethylenediamlne transition metal complexes, the hydrogen bonding and the presence of ZnCl₄ further complicates the vibrational spectra. With a view to study this, the present study of dihydridobis (ethylenedianlne) osnlum tetrachloro zincate was carried out.     

Vibrational properties of polysiloxanes: from dimer to oligomers and polymers. 1. Structural and vibrational properties of hexamethyldisiloxane (CH3)3SiOSi(CH3)3

The hexamethyldisiloxane (HMDS)(CH₃)₃SiOSi(CH₃)₃ molecule is one of the basic building blocks of silicones and polysiloxanes, as it is used for many chain terminations. Far‐infrared, mid‐infrared, and polarized Raman spectroscopic studies, combined with quantum chemical calculations and vibrational normal mode analyses, were performed for the HMDS molecule. The internal rotation of the trimethylsilyl group was calculated to be nearly free. The large‐amplitude bending motion was found very anharmonic with a barrier to linearity below 4 kJ/mol. Exhaustive assignments of observed wavenumbers have been performed on the basis of calculated potential energy distributions (PED) and atomic displacements. By isotopic ¹⁶O ¹⁸O substitution, the Si O Si symmetric and antisymmetric stretching modes shift from 521 and 1074 cm⁻¹ to 514 and 1028 cm⁻¹, respectively. This spectroscopic observation provides convincing evidence that the molecule is bent with an angle estimated at around 150°. The comparison of HMDS vibrational spectra with the vibrational spectra of some siloxane derivatives reveals strong effects of silicon substituents on the Si O Si symmetric and antisymmetric stretchings. The Si O Si siloxane bridge group plays a key role in the properties of the HMDS molecule and may also account for some important silicone polymer properties such as their very low glass transition, their high compressibility, and their low surface tension. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational Spectra of 4-Benzoylpiridine and the 18O Substituted Derivative

Abstract

Infrared and Raman spectra of 4-benzoylpiridine (4BP) and its ¹⁸O substituted derivative have been recorded in the solid and in the molten state. Polarized Raman spectra in the molten state have also been measured. The assignment of the vibrational bands is performed on the basis of isotopic shifts, group vibrational concept and polarization features of the normal modes. The previous assignment of the in- and out-of-plane deformations of the carbonyl group and the fundamentals below 700 cm^?1 are questioned and corrected.     

Experimental (UV,NMR, IR and Raman) and theoretical spectroscopic properties of 2-chloro-6-methylaniline

In this work, the experimental and theoretical UV, NMR and vibrational spectra of 2-chloro-6-methylaniline (2-Cl-6-MA, C₇H₈NCl) were studied. The ultraviolet absorption spectra of compound that dissolved in ethanol were examined in the range of 200–400 nm. The ¹H, ¹³C and DEPT NMR spectra of the compound were recorded. FT-IR and FT-Raman spectra of 2-Cl-6-MA in the liquid phase were recorded in the region 4000–400 cm^?1 and 3500–50 cm^?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using density functional theory (DFT) employing B3LYP exchange correlation and the 6-311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT-IR and FT-Raman spectra. The observed and calculated frequencies were found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. Isotropic chemical shifts were calculated using the gauge-invariant atomic orbital (GIAO) method. Comparison of the calculated NMR chemical shifts and absorption wavelengths with the experimental values revealed that DFT method produces good results.     

Laser Raman Spectra of Crystalline Chloromercurate(II) Complexes

Abstract

The laser Raman spectra of crystalline [(CH₃)₄N] HgCl₃ and [(CH₃)₄N]₂HgCl₄ have been studied in the 400–20 cm^?1 region. All expected Raman active modes for the HgCl₃ ^? and HgCl₄ ^?2 ions are observed and assignments of the vibrational frequencies are made in relation to the structure of the anions.     

The Vibrational Spectra of a Series of Simple Phosphorus/Chromium Polyoxoanions

The infrared and Raman spectra of polycrystalline samples of K₂HPCr₂O₁₀, Na₃PCr₃O₁₃.3H₂0, K₃PCr₄O₁₆ and (NH₄)₃PCr₄O₁₆ were recorded and discussed. A general vibrational assignment for the internal vibrations of these species is proposed.

The structural characteristics of an interesting series of simple polyoxoanions of the PCr_nO^3- _3n+4 type have been determined recently^1–7. These species are essentially built from a central PO₄ -tetrahedron which share a different number of corners with CrO₄ -tetrahedra.

As part of our present studies on different physico-chemical properties of polyoxoanions, we have investigated the vibrational spectra of crystalline species containing the following anions: HPCr₂O^2- ₁₀, PCr₃O^3- ₁₃ and PCr₄O^3- ₁₆.

As the three species have some common structural features, their vibrational spectra can be analyzed and compared in terms of these common building elements, i. e., terminal CrO₃ and PO groups and POCr bridges.

The interatomic distances in the above mentioned units are also very similar in all the anions and the Cr-O distances are similar to those found in the normal (triclinic) form of K₂Cr₂O₇ ⁸.     

New interpretations of XPS spectra of nickel metal and oxides

A current interpretation of XPS spectra of Ni metal assumes that the main 6 eV satellite is due to a two hole c3d⁹4s² (c is a core hole) final state effect. We report REELS observation in AES at low voltages of losses (plasmons and inter-band transitions) corresponding to the satellite structures in Ni metal 2p spectra. The satellite near 6 eV is attributed to a predominant surface plasmon loss. A current interpretation of Ni 2p spectra of oxides and other compounds is based on charge transfer assignments of the main peak at 854.6 eV and the broad satellite centred at around 861 eV to the cd⁹L and the unscreened cd⁸ final-state configurations, respectively (L is a ligand hole). Multiplet splittings have been shown to be necessary for assignment of Fe 2p and Cr 2p spectral profiles and chemical states. The assignments of Ni 2p states are re-examined with intra-atomic multiplet envelopes applied to Ni(OH)₂, NiOOH and NiO spectra. It is shown that the free ion multiplet envelopes for Ni²⁺ and Ni³⁺ simulate the main line and satellite structures for Ni(OH)₂ and NiOOH. Fitting the NiO Ni 2p spectral profile is not as straightforward as the hydroxide and oxyhydroxide. It may involve contributions from inter-atomic, non-local electronic coupling and screening effects with multiplet structures significantly different from the free ions as found for MnO. A scheme for fitting these spectra using multiplet envelopes is proposed.     

Experimental and theoretical FT‐IR and FT‐Raman spectroscopic analysis of N1‐methyl‐2‐chloroaniline

In this work, the experimental and theoretical vibrational spectra of N1‐methyl‐2‐chloroaniline (C₇H₈NCl) were studied. FT‐IR and FT‐Raman spectra of the title molecule in the liquid phase were recorded in the region 4000–400 cm^?1 and 3500–50 cm^?1, respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (B3LYP) with the 6‐311++G(d,p) basis set. The vibrational frequencies were calculated and scaled values were compared with experimental FT‐IR and FT‐Raman spectra. The observed and calculated frequencies are found to be in good agreement. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. ¹³C and ¹H NMR chemical shifts results were compared with the experimental values. The optimized geometric parameters (bond lengths and bond angles) were given and are in agreement with the corresponding experimental values of aniline and p‐methyl aniline. Copyright © 2008 John Wiley & Sons, Ltd.     

Density functional theory calculation and vibrational spectral analysis of 4‐hydroxy‐3‐(3‐oxo‐1‐phenylbutyl)‐2H‐1‐benzopyran‐2‐one

The Fourier transform infrared (4000–400 cm⁻¹) and Fourier transform Raman (3500–500 cm⁻¹) spectra of 4‐hydroxy‐3‐(3‐oxo‐1‐phenylbutyl)‐2H‐1‐benzopyran‐2‐one (Warfarin) have been measured and calculated. The structure optimization has been made using density functional theory (DFT) calculations. Complete vibrational assignments of the observed spectra have been compared with theoretical wavenumbers. The wavenumber increasing in the methyl group shows the electronic hyperconjugation effect. The natural bond orbital (NBO) analysis reveals the hyperconjugation interaction and the intramolecular hydrogen bonding. The first‐order hyperpolarizability has been calculated. Copyright © 2009 John Wiley & Sons, Ltd.