Raman Spectra Of Aqueous Solutions Research Articles

Raman Spectra of Alkali Metal Oxalates in Aqueous Solution. Evidence for Ion-pair Formation

Abstract Laser Raman spectra of aqueous solutions of lithium, potassium, and caesium oxalates have been obtained; their band contours were examined by curve analysis. The intensities of several bands show distinct concentration and cation dependences. This behavior is connected with the ion-pair formation of oxalate ions with alkali metal cations. The assignments of C=O stretching vibrations are also discussed.

Analysis of Inorganic Builders in Detergent Powders by Laser Raman Spectrometry

The analysis of inorganic builders in detergent powders was studied by means of laser Raman spectrometry after the extraction with 95% ethanol. The Raman spectra of aqueous solutions of typical inorganic builders, that is, sodium tripolyphosphate (Na5P3O10), sodium pyrophosphate (Na4P2O7), sodium carbonate, and sodium sulfate, were measured. The characteristic peaks of each compound were located at 1090 cm-1, 1065 cm-1, 1020 cm', and 978 cm-1, respectively. We found that each component was able to be readily detected from Raman spectra of mixtures of four compounds. The Raman spectra were applied to the analysis of some commercial detergent powders and it was clarified that builders of each of the samples can be readily identified by the characteristic peaks mentioned above. The determination of Na5P3O10, Na4P2O7, Na2CO3, and Na2SO4 in the detergent powders were made by using sodium formate as an internal standard. It was shown that the analytical curve for each component exhibits a good linearity, and quantity of each of the builders in commercial detergent powders can be determined with good precision.

Laser Raman Light-Scattering Observations of Conformational Changes in Myosin Induced by Inorganic Salts

The Raman spectra of aqueous solutions of myosin and mixtures of myosin in solutions of the salts CaCl(2), MgCl(2), and LiBr have been taken. The spectrum of the solvent background has been subtracted by means of a computer, leaving only the Raman peaks of the protein. From an analysis of the Raman bands in the regions at 900, 940, 1,240-1,300, and 1,650-1,670 cm(-1), it seems likely that CaCl(2) effects an alpha-to beta-transition in myosin, probably owing to the interaction of the Ca(2+) ion, LiBr appears to denature the protein leading to increased random coil structure, and MgCl(2) appears to have an effect intermediate between the two other salts. These results are reported for concentrations as low as 10(-5) M of CaCl(2) and MgCl(2).This investigation indicates the usefulness of the Raman light-scattering technique for the study of protein conformational changes.

Spectres Raman de Résonance de la Diéthylcyanine

AbstractThe resonance Raman spectra of aqueous solutions of the diettylcyanine ion are recorded from 100–4000 cm−1 using all the exciting lines of an Ar+ laser and the 6328 Å line of a HeNe laser. Experimental results, intensities and depolarization ratios, are discussed using Albrecht's theory. The calculated and experimental intensity laws obtained for some normal modes are analysed. An assignment of all the Raman bands is proposed, based upon comparison with infrared spectra and the results of a normal modes calculation.

A Raman spectroscopic study of the mono- and di-protonated ethylenediaminetetra-acetate ions

Raman spectra of aqueous solutions of Na+ and ethylenediaminetetra-acetate (edta) at pH 4.5–13 have been obtained together with those of a number of related solid complexes of edta. Analysis of the data suggests that the Hedta3– ion adopts a configuration, at pH 7.5 in water, in which both nitrogens are equally protonated and hydrogen bonds are formed to two carboxylate groups. The configuration of the H2edta2– ion is probably similar, but involves hydrogen bonds to four carboxylate groups.

Formation of dimeric mercury(II) thiolate ions in water

Methanethiolatomercury(II) acetate dissolves in water to a form conducting solutions. Mercury-sulphur stretching vibrations in mercuryII) thiolates Hg(SR)2 occur in the range 371 (or 405)-172 cm-1, and Raman spectra of aqueous solutions of MeSHg02CMe and related complexes have an intense, broad, strongly polarized band in the range 277-253 cm-1. With the polarized band assigned as a totally symmetric mercury-sulphur stretching mode the ions containing mercury are assumed to have structure with tetrahedral coordination and a centre of symmetry between mercury atoms. Similar sulphur bridging occurs in polymeric bis(tert-butylthiolato)mercury(II)

Raman spectra of aqueous solutions of hydrolysed aluminium(III) salts

The hydrolysis of aluminum salts in aqueous solution has been studied by Raman spectroscopy. Evidence for the occurrence of the ion [Al13O4(OH)24(OH2)12]7+ in solutions containing a formal [OH–] : [Al3+] ratio of 2.5 : 1 is provided by comparisons with the spectra of crystalline compounds containing this ion. The presence of other polymeric species in less highly hydrolysed solutions cannot be confirmed.

Theoretical infrared and Raman spectroscopic parameters for H2O and the H2O ? Li+ system

The force constants of symmetric OH stretching and HOH bending vibrations in H2O and H2O ⋯ Li+ and the i.r. and Raman intensities of the corresponding bands are computed by using the ab initio SCF LCAO MO approach. A comparison of the calculated data for H2O and H2O ⋯ Li+ shows that: (i) the cation–water interaction does not substantially affect the vibration frequencies of H2O, (ii) the i.r. intensities increase considerably for both bands, and (iii) the Raman intensities of ν1 and ν2 decrease due to the cation–water interaction. The results of calculations are used for the discussion of the i.r. and Raman spectra of aqueous solutions of electrolytes. Some proposals concerning the interpretation of the absence of the cation effects in these spectra are made.

Raman pH profiles for nucleic acid constituents II. 5′-AMP and 5′-GMP ribonucleotides

Raman spectra of aqueous solutions of 5′-AMP and 5′-GMP have been recorded as a function of pH. Band intensities and frequencies have been monitored to determine bands which may be considered as diagnostic for the concentration and the pK of the solution species. Quantitative band intensity measurements indicate only a selected number of bands can be considered as diagnostic of the base or the secondary phosphate proton dissociation. The utility of the pH profiles derived from specific band intensity variations for 5′-AMP is discussed in terms of the effect of acidification on solution characteristics of polyadenylic acid.

Raman pH profiles for nucleic acid constituents I. Cytidine and uridine ribonucleosides

Raman spectra of aqueous solutions of uridine and cytidine have been recorded as a function of pH with the band intensities and vibrational frequencies monitored to determine bands which may be considered as diagnostic of the concentration of the various species. Quantitative band intensity measurements indicate that not all pH-sensitive bands can be considered as diagnostic of the pK value for the acid form of the nucleoside, and for the percent species in solution. Although the accuracy of the Raman band intensity method is inherently less than that of the titrimetric or visible-ultraviolet spectrophotometric methods, the pK values and percent species agree well with those obtained from these methods. The utility of the results obtained from the pH profiles for cytidine is discussed in terms of the effect of acidification on the structural and conformational characteristics of polycytidylic acid in solution.

A raman spectral study of ion pair formation in aqueous solutions of strontium nitrate

Raman spectra of aqueous solutions containing Sr2+ and NO 3 − exhibit lines characteristic of Sr(NO3)+ and Sr(NO3)2 in addition to those of the solvated nitrate ion. Intensities have been measured, and the quantities nobs, the average ligand number, andC F, the concentration of free nitrate ion have been evaluated. From these data two cumulative formation constants have been estimated for 25°C: β1=0.76±0.10 and β2=0.10±0.02. The dependence of the results on experimental limitations is discussed.

Raman Spectral Studies of Cadmium–Nitrite Interactions in Aqueous Solutions and Crystals

Raman spectra of aqueous solutions containing Cd2+ and NO2− clearly reveal the presence of solvated nitrite ion and of complexes. A band at 861 cm−1 is characteristic of the latter. The free nitrite concentration was measured from the intensity of the 817 cm−1 line and the average ligand number was evaluated for solutions with composition prescribed by the mole-ratio method. Four cumulative formation constants were deduced: β1 = 61.6; β2 = 993; β3 = 2390; β4 = 1899. Evidence that nitrite chelates Cd2+ through the two oxygen atoms is presented. The diagnostic spectral evidence consists of a high intensity, high frequency deformation mode and low intensity N—O stretching Raman bands with frequencies almost identical to those of the solvated nitrite ion. Data are also presented for solid Cd(NO2)2 and Kx−2Cd(NO2)x(x = 3,4,5).

Raman spectral investigation of the interactions between group II cations and ethylene glycol in aqueous solutions

Studies of the Raman spectra of aqueous solutions of ethylene glycol (EG) containing Group II cations revealed that calcium, zinc, and strontium ions bring about significant changes in the C–C and C–O stretching regions, while magnesium, cadmium, and barium ions result in only minor changes primarily in the C–O stretching region. These changes were compared with the effects of some of the ions on a series of related molecules including methanol and ethanol, the cyclohexane-1,2-diols, and ethylenediamine. The results indicate that the effects of calcium, zinc, or strontium ions on the spectrum of EG are most consistent with bidentate co-ordination of the metal ions and an attendant conversion of ethylene glycol from trans- to gauche- form. The minor changes arising from the presence of magnesium, cadmium, or barium ions are those expected from monodentate co-ordination. The i.r. spectra of solutions of calcium chloride in ethylene glycol reveal changes which are consistent with the interpretation of the Raman spectra.

ChemInform Abstract: VIBRATIONAL SPECTRA OF SQUARE‐PLANAR TETRAHALOGENO‐GOLD(III)‐PALLADIUM(II), AND ‐PLATINUM(II) ANIONS IN SOLUTION

I.r. and Raman spectra of the salts R4N[AuX4][R = Bun or Pnn(n-pentyl), X = Cl or Br] and (R4N)2[MX4](R = Bun or Pnn; M = Pd, X = Cl; M = Pt, X = Cl or Br) in solution are reported, together with the i.r. spectrum of a solid containing (Bun4N)2[PdBr4] and Raman spectra of aqueous solutions containing the above anions and [PtI4]2–. Studies of the solvent dependence of the Raman frequencies of [AuCl4]– and the cation dependence of vibrational frequencies of solid R4N[AuCl4](R = Me, Et, Prn, Bun, or Pnn) have also been made. The inactive B2u mode has been deduced as 112 cm–1 from a study of the combination bands of solid Cs[AuCl4]. The most consistent sets of vibrational frequencies have been used to recalculate force constants.

Resonance Raman spectra of protohemin and protohemin‐imidazole complex

AbstractResonance Raman spectra of aqueous solutions of protohemin and its complex with imidazole have been obtained using several exciting lines from Ar+ and HeCd lasers. The effects of different axial ligands to iron in hemin are reflected in the resonance Raman spectra of their respective complexes. Within experimental limits, hemin does not show any anomalously polarized bands (Q1 > ¾) while its complex with imidazole shows several such bands when excitation is in the α and β absorption regions. When excitation is in the Soret region, a polarized band ∼ 1500 cm−1 appears in the spectra of hemin‐imidazole complex and heme proteins. It is proposed as a spin state marker as well as to characterize the position of the iron ion relative to the porphyrin plane.Excitation profiles for some of the bands of hemin confirm the assigment of the α band near 5300 Å in the unresolved visible absorption spectrum.

Vibrational spectra of square-planar tetrahalogeno-gold(III), -palladium(II), and -platinum(II) anions in solution

I.r. and Raman spectra of the salts R4N[AuX4][R = Bun or Pnn(n-pentyl), X = Cl or Br] and (R4N)2[MX4](R = Bun or Pnn; M = Pd, X = Cl; M = Pt, X = Cl or Br) in solution are reported, together with the i.r. spectrum of a solid containing (Bun4N)2[PdBr4] and Raman spectra of aqueous solutions containing the above anions and [PtI4]2–. Studies of the solvent dependence of the Raman frequencies of [AuCl4]– and the cation dependence of vibrational frequencies of solid R4N[AuCl4](R = Me, Et, Prn, Bun, or Pnn) have also been made. The inactive B2u mode has been deduced as 112 cm–1 from a study of the combination bands of solid Cs[AuCl4]. The most consistent sets of vibrational frequencies have been used to recalculate force constants.

Raman studies of nucleic acids X. Conformational structures of Escherichia coli transfer RNAs in aqueous solution

Laser-excited Raman spectra of aqueous solutions of purified samples of Escherichia coli tRNA Glu, tRNA Arg, tRNA Val, tRNA fMet and tRNA 2 Phe are compared. The characteristic Raman frequencies and intensities, from scattering by symmetrical stretching vibrations of the phosphodiester groups, reveal that the total secondary structure of each tRNA is qualitatively and quantitatively the same. The percentage of nucleotide residues in each tRNA which exist in a highly ordered configuration is 84 ± 4 %, consistent with a cloverleaf structure provided two-thirds of the unpaired bases in loops are also in ordered configurations. The remaining nucleotides (16 ± 4 %) must occur in randomly oriented or highly-strained configurations of the tRNA chain. The Raman spectra also reveal specific differences in the amount of stacking of A and G residues in different tRNAs. These results provide strong evidence for the presence of specific tertiary structure (folding) in aqueous tRNA. A study of the melting transition of tRNA Glu over the range 32–90 °C reveals that appreciable order persists in the tRNA backbone at 90 °C and is attributable to residual stacking of the purines. Gross changes in the conformation of tRNA Val are also detected when excess Mg 2+ is present. The improved spectral sensitivity in this work demonstrates that the Raman spectrum of tRNA may be used to detect the presence of the minor nucleoside, dihydrouridine, and that the frequency region 1150–1450 cm −1 is highly sensitive to the base composition, base sequence and base-stacked secondary structure of tRNA.

Raman spectrometric studies of aqueous borate complexes with ethylene glycol and mannitol

Raman spectra of aqueous solutions of borate anion containing ethylene glycol and mannitol have been obtained. These have been shown to be consistent with 1:1 and 2:1 polyol:borate complexes. On the basis of comparison to the spectra of free ethylene glycol it is proposed that the 2:1 complex has C 2 symmetry, i.e. the 5-membered chelate ring is non planar. Assignments of vibrational frequencies associated with BO bonds are discussed.

A vibrational-spectroscopic study of the species present in the CO2?H2O system

Raman and infrared spectra have been recorded of water and heavy-water solutions of carbon dioxide, potassium bicarbonate, and potassium carbonate. The structures of the carbonate and bicarbonate ions and CO2 (aqueous solution) have been determined from a consideration of Raman and infrared data. The results reveal the presence of solvent effects in the carbonate and CO2 water solutions. No bands characteristic of H2CO3 were observed in the Raman spectrum of aqueous solutions of CO2.

Anomalous Behavior of 18O-Labeled Compounds. VI. The Vibrational Spectra of Isotopic Metaborates

The infrared absorption spectrum of an aqueous solution of 18O-labeled sodium metaborate shows the antisymmetric B–18O stretching ν3 fundamental of its B(OH)4− ions at 982 cm−1, as compared with the frequency of 958 cm−1 observed for the respective normal borate vibration. The Raman spectrum of aqueous solutions of these borates exhibits their symmetric B–O stretching ν1 fundamental in both cases at 744 cm−1. The fact that the ν1 and ν3 frequencies of the hydrated B(18OH)4− ions are not decreased by the 16O–18O exchange is taken to indicate that the hydrogen bonding between the B(OH)4− ions and their solvating water molecules is appreciably lower in the case of the 18O-labeled ions than in the case of the B(16OH)4− ions.