The Experts below are selected from a list of 6645 Experts worldwide ranked by ideXlab platform

Shin-ichi Ishiguro - One of the best experts on this subject based on the ideXlab platform.

  • Solvation Number and conformation of N,N -dimethylacrylamide and N,N -dimethylpropionamide in the coordination sphere of the cobalt(II) ion in solution studied by FT-IR and FT-raman spectroscopy
    Analytical sciences : the international journal of the Japan Society for Analytical Chemistry, 2007
    Co-Authors: Mitsunori Asada, Takushi Mitsugi, Takahiro Ogura, Kenta Fujii, Yasuhiro Umebayashi, Shin-ichi Ishiguro
    Abstract:

    The Solvation Number and conformation of N,N-dimethylacrylamide (DMAA) in the coordination sphere of the cobalt(II) ion in solution were studied, and compared with those of N,N-dimethylpropionamide (DMPA) by means of FT-Raman and FT-IR spectroscopy. Both solvents are present as either the planar cis or nonplanar staggered conformer in equilibrium, and the former is more stable in the bulk. As these solvents solvate the metal ion through the carbonyl O atom of the acryl (DMAA) or propionyl (DMPA) group, the Solvation structure around the metal ion is highly congested to reduce the Solvation Number and/or to lead to a conformational geometry change of solvent. It turns out that the Solvation Number of the cobalt(II) ion is 4 for both DMAA and DMPA at 298 K, and that DMPA changes its conformation upon Solvation, whereas DMAA hardly changes. The enthalpy of conformational change ΔH° for DMPA is 5 kJ mol-1 in the bulk, and is -9 kJ mol-1 in the coordination sphere of the cobalt(II) ion. On the other hand, the ΔH° value for DMAA is 9 kJ mol-1 in the bulk.

  • Solvation structure of magnesium, zinc, and alkaline earth metal ions in N,N-dimethylformamide, N,N-dimethylacetamide, and their mixtures studied by means of Raman spectroscopy and DFT calculations—Ionic size and electronic effects on steric congesti
    Journal of Raman Spectroscopy, 2007
    Co-Authors: Mitsunori Asada, Kenta Fujii, Yasuhiro Umebayashi, Takao Fujimori, Ryo Kanzaki, Shin-ichi Ishiguro
    Abstract:

    The Solvation structure of magnesium, zinc(II), and alkaline earth metal ions in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA), and their mixtures has been studied by means of Raman spectroscopy and DFT calculations. The Solvation Number is revealed to be 6, 7, 8, and 8 for Mg2+, Ca2+, Sr2+, and Ba2+, respectively, in both DMF and DMA. The δ (OCN) vibration of DMF shifts to a higher waveNumber upon binding to the metal ions and the shift Δν(= νbound − νfree) becomes larger, when the ionic radius of the metal ion becomes smaller. The ν (NCH3) vibration of DMA also shifts to a higher waveNumber upon binding to the metal ions. However, the shift Δν saturates for small ions, as well as the transition-metal (II) ions, implying that steric congestion among solvent molecules takes place in the coordination sphere. It is also indicated that, despite the magnesium ion having practically the same ionic radius as the zinc(II) ion of six-coordination, their Solvation Numbers in DMA are significantly different. DFT calculations for these metalsolvate clusters of varying Solvation Numbers revealed that not only solvent–solvent interaction through space but also the bonding nature of the metal ion plays an essential role in the steric congestion. The individual Solvation Number and the Raman shift Δν in DMF–DMA mixtures indicate that steric congestion is significant for the magnesium ion, but not appreciable for calcium, strontium, and barium ions, despite the Solvation Number of these metal ions being large. Copyright © 2006 John Wiley & Sons, Ltd.

  • Characterization of Metal Ions in Coordinating Solvent Mixtures by Means of Raman Spectroscopy
    Analytical sciences : the international journal of the Japan Society for Analytical Chemistry, 2004
    Co-Authors: Shin-ichi Ishiguro, Yasuhiro Umebayashi, Ryo Kanzaki
    Abstract:

    Titration Raman spectroscopy has been developed for studying the Solvation structure of metal ions in solution. The method affords us the Solvation Number, and the value thus obtained in neat solvents is in good agreement with that determined by EXAFS. The method is then applied to solvent mixtures, and the individual Solvation Number for each solvent is extracted. In a solvent mixture of N,N-dimethylformamide (DMF) and N,N,N',N'-tetramethylurea (TMU), the metal ion prefers DMF to TMU, which is ascribed to the Solvation steric effect. The same applies also for the solvent mixture of N,N-dimethylpropionamide (DMPA) and DMF. However, unlike TMU, DMPA changes its conformation from the planar cis to non-planar staggered upon Solvation to the metal ion. The enthalpy for the conformational change of DMPA is positive in the bulk, while it is significantly negative in the coordination sphere of the manganese(II) ion. Here, we briefly describe the procedure of measurements and analyses for the titration Raman spectroscopy, and review the Solvation structure of the alkaline earth, first transition metal(II) and lanthanide(III) ions in some solvent mixtures in view of Solvation steric effect.

  • Solvation structure of lanthanide(III) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide studied by titration Raman spectroscopy
    Physical Chemistry Chemical Physics, 2002
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Isamu Mekata, Shin-ichi Ishiguro
    Abstract:

    The Raman spectra of neodymium(III), gadolinium(III) and thulium(III) perchlorate solutions of varying salt molalities were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. In DMF–DMA mixtures, the magnitude of the shift for the δ(OC–N) and ν(N–CH3) vibrations of bound solvent molecules, ΔνDMF, and ΔνDMA, respectively, depends on the solvent composition, and the variation profile of ΔνDMA is in parallel with that of the Ln–O(solvent) bond length. The Number of solvent molecules bound to the metal ion or the individual Solvation Number in a solvent mixture, nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It is indicated that a strong Solvation steric effect operates among bound solvent molecules, i.e., the total Solvation Number decreases with increasing DMA content, and the variation profile depends on the metal ion. The individual Solvation Number of DMA was found to be 3 at around xDMA = 0.4 for all the metal systems examined.

  • Individual Solvation Number of first-row transition metal(II) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide—Solvation steric effect
    Physical Chemistry Chemical Physics, 2001
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Manabu Watanabe, Shin-ichi Ishiguro
    Abstract:

    Raman spectra of solutions of manganese(II), nickel(II), copper(II) and zinc(II) perchlorate with varying molality were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. These Raman spectra were deconvoluted and the bound solvent bands (νbound) to the metal ion were extracted from the free solvent band (νfree). The Number of solvent molecules bound to the metal ion or the individual Solvation Number n in a solvent mixture, i.e., nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It turned out that the manganese(II) ion is six-coordinated over the whole solvent composition range in the mixtures, i.e., nDMF + nDMA = 6, and the relationship nDMF/nDMA = xDMF/xDMA, where x denotes the mole fraction of the solvent, holds in the mixture. With regard to the zinc(II) ion, the total Solvation Number decreases from 6 with increasing xDMA in the mixtures. In neat DMA, two bound solvent bands are extracted, indicating that two species, Zn(DMA)62+ and Zn(DMA)42+, coexist in equilibrium. With the six-coordinate zinc(II) solvated ion, the relationship nDMF/nDMA > xDMF/xDMA holds in the mixture. This shows that the Solvation steric effect of DMA operates for the six-coordinate zinc(II) solvated ion, unlike for the manganese(II) one. The copper(II) ion is six-coordinated, although the coordination structure is strongly distorted owing to the Jahn–Teller effect. Indeed, two bands ascribable to the solvents bound at the equatorial and axial positions were extracted. In the mixtures, the relationship nDMF/nDMA > xDMF/xDMA holds for solvents bound at the equatorial position, i.e., the Solvation steric effect operates among solvent molecules, while the relationship nDMF/nDMA ⩽ xDMF/xDMA holds for solvents bound at the axial position. This is expected because the Cu–O(solvent) bond length is longer for the solvent at the axial position, and the electron-pair donating ability is slightly stronger for DMA. The magnitude of the shift Δν (=νbound − νfree) depends strongly on the metal ion. Indeed, the Δν values in neat DMF and DMA vary according to the relationship Δν = (ar)−n, a function of the ionic radius r of the metal ion, and the parameters a and n were evaluated. The shift Δν in the mixtures implies that the M–O(DMF) bond length in the M(DMF)6−n(DMA)n2+ solvated ion is elongated with increasing coordination Number nDMA of DMA.

Yasuhiro Umebayashi - One of the best experts on this subject based on the ideXlab platform.

  • Solvation Number and conformation of N,N -dimethylacrylamide and N,N -dimethylpropionamide in the coordination sphere of the cobalt(II) ion in solution studied by FT-IR and FT-raman spectroscopy
    Analytical sciences : the international journal of the Japan Society for Analytical Chemistry, 2007
    Co-Authors: Mitsunori Asada, Takushi Mitsugi, Takahiro Ogura, Kenta Fujii, Yasuhiro Umebayashi, Shin-ichi Ishiguro
    Abstract:

    The Solvation Number and conformation of N,N-dimethylacrylamide (DMAA) in the coordination sphere of the cobalt(II) ion in solution were studied, and compared with those of N,N-dimethylpropionamide (DMPA) by means of FT-Raman and FT-IR spectroscopy. Both solvents are present as either the planar cis or nonplanar staggered conformer in equilibrium, and the former is more stable in the bulk. As these solvents solvate the metal ion through the carbonyl O atom of the acryl (DMAA) or propionyl (DMPA) group, the Solvation structure around the metal ion is highly congested to reduce the Solvation Number and/or to lead to a conformational geometry change of solvent. It turns out that the Solvation Number of the cobalt(II) ion is 4 for both DMAA and DMPA at 298 K, and that DMPA changes its conformation upon Solvation, whereas DMAA hardly changes. The enthalpy of conformational change ΔH° for DMPA is 5 kJ mol-1 in the bulk, and is -9 kJ mol-1 in the coordination sphere of the cobalt(II) ion. On the other hand, the ΔH° value for DMAA is 9 kJ mol-1 in the bulk.

  • Solvation structure of magnesium, zinc, and alkaline earth metal ions in N,N-dimethylformamide, N,N-dimethylacetamide, and their mixtures studied by means of Raman spectroscopy and DFT calculations—Ionic size and electronic effects on steric congesti
    Journal of Raman Spectroscopy, 2007
    Co-Authors: Mitsunori Asada, Kenta Fujii, Yasuhiro Umebayashi, Takao Fujimori, Ryo Kanzaki, Shin-ichi Ishiguro
    Abstract:

    The Solvation structure of magnesium, zinc(II), and alkaline earth metal ions in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA), and their mixtures has been studied by means of Raman spectroscopy and DFT calculations. The Solvation Number is revealed to be 6, 7, 8, and 8 for Mg2+, Ca2+, Sr2+, and Ba2+, respectively, in both DMF and DMA. The δ (OCN) vibration of DMF shifts to a higher waveNumber upon binding to the metal ions and the shift Δν(= νbound − νfree) becomes larger, when the ionic radius of the metal ion becomes smaller. The ν (NCH3) vibration of DMA also shifts to a higher waveNumber upon binding to the metal ions. However, the shift Δν saturates for small ions, as well as the transition-metal (II) ions, implying that steric congestion among solvent molecules takes place in the coordination sphere. It is also indicated that, despite the magnesium ion having practically the same ionic radius as the zinc(II) ion of six-coordination, their Solvation Numbers in DMA are significantly different. DFT calculations for these metalsolvate clusters of varying Solvation Numbers revealed that not only solvent–solvent interaction through space but also the bonding nature of the metal ion plays an essential role in the steric congestion. The individual Solvation Number and the Raman shift Δν in DMF–DMA mixtures indicate that steric congestion is significant for the magnesium ion, but not appreciable for calcium, strontium, and barium ions, despite the Solvation Number of these metal ions being large. Copyright © 2006 John Wiley & Sons, Ltd.

  • Characterization of Metal Ions in Coordinating Solvent Mixtures by Means of Raman Spectroscopy
    Analytical sciences : the international journal of the Japan Society for Analytical Chemistry, 2004
    Co-Authors: Shin-ichi Ishiguro, Yasuhiro Umebayashi, Ryo Kanzaki
    Abstract:

    Titration Raman spectroscopy has been developed for studying the Solvation structure of metal ions in solution. The method affords us the Solvation Number, and the value thus obtained in neat solvents is in good agreement with that determined by EXAFS. The method is then applied to solvent mixtures, and the individual Solvation Number for each solvent is extracted. In a solvent mixture of N,N-dimethylformamide (DMF) and N,N,N',N'-tetramethylurea (TMU), the metal ion prefers DMF to TMU, which is ascribed to the Solvation steric effect. The same applies also for the solvent mixture of N,N-dimethylpropionamide (DMPA) and DMF. However, unlike TMU, DMPA changes its conformation from the planar cis to non-planar staggered upon Solvation to the metal ion. The enthalpy for the conformational change of DMPA is positive in the bulk, while it is significantly negative in the coordination sphere of the manganese(II) ion. Here, we briefly describe the procedure of measurements and analyses for the titration Raman spectroscopy, and review the Solvation structure of the alkaline earth, first transition metal(II) and lanthanide(III) ions in some solvent mixtures in view of Solvation steric effect.

  • Solvation structure of lanthanide(III) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide studied by titration Raman spectroscopy
    Physical Chemistry Chemical Physics, 2002
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Isamu Mekata, Shin-ichi Ishiguro
    Abstract:

    The Raman spectra of neodymium(III), gadolinium(III) and thulium(III) perchlorate solutions of varying salt molalities were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. In DMF–DMA mixtures, the magnitude of the shift for the δ(OC–N) and ν(N–CH3) vibrations of bound solvent molecules, ΔνDMF, and ΔνDMA, respectively, depends on the solvent composition, and the variation profile of ΔνDMA is in parallel with that of the Ln–O(solvent) bond length. The Number of solvent molecules bound to the metal ion or the individual Solvation Number in a solvent mixture, nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It is indicated that a strong Solvation steric effect operates among bound solvent molecules, i.e., the total Solvation Number decreases with increasing DMA content, and the variation profile depends on the metal ion. The individual Solvation Number of DMA was found to be 3 at around xDMA = 0.4 for all the metal systems examined.

  • Individual Solvation Number of first-row transition metal(II) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide—Solvation steric effect
    Physical Chemistry Chemical Physics, 2001
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Manabu Watanabe, Shin-ichi Ishiguro
    Abstract:

    Raman spectra of solutions of manganese(II), nickel(II), copper(II) and zinc(II) perchlorate with varying molality were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. These Raman spectra were deconvoluted and the bound solvent bands (νbound) to the metal ion were extracted from the free solvent band (νfree). The Number of solvent molecules bound to the metal ion or the individual Solvation Number n in a solvent mixture, i.e., nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It turned out that the manganese(II) ion is six-coordinated over the whole solvent composition range in the mixtures, i.e., nDMF + nDMA = 6, and the relationship nDMF/nDMA = xDMF/xDMA, where x denotes the mole fraction of the solvent, holds in the mixture. With regard to the zinc(II) ion, the total Solvation Number decreases from 6 with increasing xDMA in the mixtures. In neat DMA, two bound solvent bands are extracted, indicating that two species, Zn(DMA)62+ and Zn(DMA)42+, coexist in equilibrium. With the six-coordinate zinc(II) solvated ion, the relationship nDMF/nDMA > xDMF/xDMA holds in the mixture. This shows that the Solvation steric effect of DMA operates for the six-coordinate zinc(II) solvated ion, unlike for the manganese(II) one. The copper(II) ion is six-coordinated, although the coordination structure is strongly distorted owing to the Jahn–Teller effect. Indeed, two bands ascribable to the solvents bound at the equatorial and axial positions were extracted. In the mixtures, the relationship nDMF/nDMA > xDMF/xDMA holds for solvents bound at the equatorial position, i.e., the Solvation steric effect operates among solvent molecules, while the relationship nDMF/nDMA ⩽ xDMF/xDMA holds for solvents bound at the axial position. This is expected because the Cu–O(solvent) bond length is longer for the solvent at the axial position, and the electron-pair donating ability is slightly stronger for DMA. The magnitude of the shift Δν (=νbound − νfree) depends strongly on the metal ion. Indeed, the Δν values in neat DMF and DMA vary according to the relationship Δν = (ar)−n, a function of the ionic radius r of the metal ion, and the parameters a and n were evaluated. The shift Δν in the mixtures implies that the M–O(DMF) bond length in the M(DMF)6−n(DMA)n2+ solvated ion is elongated with increasing coordination Number nDMA of DMA.

Jeremy Moore - One of the best experts on this subject based on the ideXlab platform.

  • Fourier transform Raman spectroscopic study of lithium perchlorate solutions in acrylonitrile
    Journal of Raman Spectroscopy, 1995
    Co-Authors: J. M. Alia, H.g.m. Edwards, Jeremy Moore
    Abstract:

    Lithium perchlorate solutions in acrylonitrile (propenenitrile), in a range of concentration between 1 and 6 molal, were studied by using Fourier transform Raman spectroscopy. The new band in the v(CN) region proceeding from the bound species Li+… (acrylonitrile)n and the modifications in the C—C stretching band were studied in detail by means of deconvolution and band-fitting procedures. An average Solvation Number of ca. 2.3 was obtained without any correction for the ion pairing. The data obtained in the analysis of the perchlorate anion v1 (symmetric stretch) band allow us to quantify the concentration of the different species (free perchlorate, solvent-separated ion pairs and contact ion pairs) present, and to obtain a more realistic Solvation Number for the lithium ion in acrylonitrile solutions. This Solvation Number was estimated at 3.0 ± 0.1.

  • Solvation of Ag+ ions in some nitriles; a Fourier transform Raman spectroscopic study
    Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1995
    Co-Authors: J. M. Alia, H.g.m. Edwards, Jeremy Moore
    Abstract:

    Abstract Silver nitrate solutions in four nitriles (acetonitrile, benzonitrile, ethylcyanoacetate and acrylonitrile), in a range of concentration between 37 and 3 molecules of solvent per mole of solute, have been studied using Fourier transform Raman spectroscopy. The new band in the ν (CN) region arising from the coordinated species Ag + … (nitrile) n has been analysed in detail by means of deconvolution and band-fitting procedures. The waveNumber shift of the new band (about 19 cm −1 ) seems to be independent of the nitrile and in all the cases studied the molar scattering factors are strongly increased due to the effect of the cation. Weak Solvation spheres around the silver ion are identified spectroscopically. An effect of the weak Solvation is the lack of a definite and constant Solvation Number for the metal ion, and only Numbers at infinite dilution can be obtained. These Solvation Numbers are two for benzonitrile and three for acrylonitrile, ethylcyanoacetate and acetonitrile. However, the Solvation Number obtained for acetonitrile in this work is important due to the effect of the Fermi resonance in the stretching bands used for calculations; because of this, the literature work for complexes in acetonitrile solution should be critically revised.

Kai Matsumoto - One of the best experts on this subject based on the ideXlab platform.

  • Solvation structure of lanthanide(III) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide studied by titration Raman spectroscopy
    Physical Chemistry Chemical Physics, 2002
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Isamu Mekata, Shin-ichi Ishiguro
    Abstract:

    The Raman spectra of neodymium(III), gadolinium(III) and thulium(III) perchlorate solutions of varying salt molalities were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. In DMF–DMA mixtures, the magnitude of the shift for the δ(OC–N) and ν(N–CH3) vibrations of bound solvent molecules, ΔνDMF, and ΔνDMA, respectively, depends on the solvent composition, and the variation profile of ΔνDMA is in parallel with that of the Ln–O(solvent) bond length. The Number of solvent molecules bound to the metal ion or the individual Solvation Number in a solvent mixture, nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It is indicated that a strong Solvation steric effect operates among bound solvent molecules, i.e., the total Solvation Number decreases with increasing DMA content, and the variation profile depends on the metal ion. The individual Solvation Number of DMA was found to be 3 at around xDMA = 0.4 for all the metal systems examined.

  • Individual Solvation Number of first-row transition metal(II) ions in solvent mixtures of N,N-dimethylformamide and N,N-dimethylacetamide—Solvation steric effect
    Physical Chemistry Chemical Physics, 2001
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Manabu Watanabe, Shin-ichi Ishiguro
    Abstract:

    Raman spectra of solutions of manganese(II), nickel(II), copper(II) and zinc(II) perchlorate with varying molality were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. These Raman spectra were deconvoluted and the bound solvent bands (νbound) to the metal ion were extracted from the free solvent band (νfree). The Number of solvent molecules bound to the metal ion or the individual Solvation Number n in a solvent mixture, i.e., nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It turned out that the manganese(II) ion is six-coordinated over the whole solvent composition range in the mixtures, i.e., nDMF + nDMA = 6, and the relationship nDMF/nDMA = xDMF/xDMA, where x denotes the mole fraction of the solvent, holds in the mixture. With regard to the zinc(II) ion, the total Solvation Number decreases from 6 with increasing xDMA in the mixtures. In neat DMA, two bound solvent bands are extracted, indicating that two species, Zn(DMA)62+ and Zn(DMA)42+, coexist in equilibrium. With the six-coordinate zinc(II) solvated ion, the relationship nDMF/nDMA > xDMF/xDMA holds in the mixture. This shows that the Solvation steric effect of DMA operates for the six-coordinate zinc(II) solvated ion, unlike for the manganese(II) one. The copper(II) ion is six-coordinated, although the coordination structure is strongly distorted owing to the Jahn–Teller effect. Indeed, two bands ascribable to the solvents bound at the equatorial and axial positions were extracted. In the mixtures, the relationship nDMF/nDMA > xDMF/xDMA holds for solvents bound at the equatorial position, i.e., the Solvation steric effect operates among solvent molecules, while the relationship nDMF/nDMA ⩽ xDMF/xDMA holds for solvents bound at the axial position. This is expected because the Cu–O(solvent) bond length is longer for the solvent at the axial position, and the electron-pair donating ability is slightly stronger for DMA. The magnitude of the shift Δν (=νbound − νfree) depends strongly on the metal ion. Indeed, the Δν values in neat DMF and DMA vary according to the relationship Δν = (ar)−n, a function of the ionic radius r of the metal ion, and the parameters a and n were evaluated. The shift Δν in the mixtures implies that the M–O(DMF) bond length in the M(DMF)6−n(DMA)n2+ solvated ion is elongated with increasing coordination Number nDMA of DMA.

  • individual Solvation Number of first row transition metal ii ions in solvent mixtures of n n dimethylformamide and n n dimethylacetamide Solvation steric effect
    Physical Chemistry Chemical Physics, 2001
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Manabu Watanabe, Shin-ichi Ishiguro
    Abstract:

    Raman spectra of solutions of manganese(II), nickel(II), copper(II) and zinc(II) perchlorate with varying molality were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane OC–N bending vibration at 660 cm−1 of DMF and the stretching N–CH3 vibration at 740 cm−1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. These Raman spectra were deconvoluted and the bound solvent bands (νbound) to the metal ion were extracted from the free solvent band (νfree). The Number of solvent molecules bound to the metal ion or the individual Solvation Number n in a solvent mixture, i.e., nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It turned out that the manganese(II) ion is six-coordinated over the whole solvent composition range in the mixtures, i.e., nDMF + nDMA = 6, and the relationship nDMF/nDMA = xDMF/xDMA, where x denotes the mole fraction of the solvent, holds in the mixture. With regard to the zinc(II) ion, the total Solvation Number decreases from 6 with increasing xDMA in the mixtures. In neat DMA, two bound solvent bands are extracted, indicating that two species, Zn(DMA)62+ and Zn(DMA)42+, coexist in equilibrium. With the six-coordinate zinc(II) solvated ion, the relationship nDMF/nDMA > xDMF/xDMA holds in the mixture. This shows that the Solvation steric effect of DMA operates for the six-coordinate zinc(II) solvated ion, unlike for the manganese(II) one. The copper(II) ion is six-coordinated, although the coordination structure is strongly distorted owing to the Jahn–Teller effect. Indeed, two bands ascribable to the solvents bound at the equatorial and axial positions were extracted. In the mixtures, the relationship nDMF/nDMA > xDMF/xDMA holds for solvents bound at the equatorial position, i.e., the Solvation steric effect operates among solvent molecules, while the relationship nDMF/nDMA ⩽ xDMF/xDMA holds for solvents bound at the axial position. This is expected because the Cu–O(solvent) bond length is longer for the solvent at the axial position, and the electron-pair donating ability is slightly stronger for DMA. The magnitude of the shift Δν (=νbound − νfree) depends strongly on the metal ion. Indeed, the Δν values in neat DMF and DMA vary according to the relationship Δν = (ar)−n, a function of the ionic radius r of the metal ion, and the parameters a and n were evaluated. The shift Δν in the mixtures implies that the M–O(DMF) bond length in the M(DMF)6−n(DMA)n2+ solvated ion is elongated with increasing coordination Number nDMA of DMA.

  • Individual Solvation Numbers around the Nickel(II) Ion in an N, N-Dimethylformamide and N, N-Dimethylacetamide Mixture Determined by Raman Spectrophotometry
    Analytical sciences : the international journal of the Japan Society for Analytical Chemistry, 2001
    Co-Authors: Yasuhiro Umebayashi, Kai Matsumoto, Manabu Watanabe, Kazusuke Katoh, Shin-ichi Ishiguro
    Abstract:

    Individual Solvation Numbers around the nickel(II) ion have been determined by titration Raman spectroscopy in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) mixtures at 298 K. The in-plane bending vibration (delta(O=C-N)) of DMF and the stretching vibration (v(N-CH3)) of DMA were used in the present analysis. These Raman bands of solvent molecules shift to higher frequencies upon coordination of the solvent molecules to the metal ion. By analyzing the band intensities of free and bound solvent molecules with increasing concentration of the metal ion, the Solvation Number around the metal ion can be evaluated. Because the individual Solvation Numbers of DMF and DMA around the nickel(II) ion in the mixture are determined independently, the total Solvation Number is obtained as their sum. It was found that the total Solvation Number remains 6 in all mixtures of the DMA mole fraction x = 0 - 1. Although DMF and DMA have practically the same electron-pair donor capacities, the nickel(II) ion prefers DMF to DMA, and an equal Solvation Number is attained at x = 0.75. This is ascribed to the Solvation steric effect of DMA.

P. H. Parsania - One of the best experts on this subject based on the ideXlab platform.

  • Effect of temperature on ultrasonic velocity and thermodynamic parameters of bisphenol-C-formaldehyde-acrylate resin solutions
    Fluid Phase Equilibria, 2007
    Co-Authors: N. M. Mehta, F. D. Karia, P. H. Parsania
    Abstract:

    Abstract The density, viscosity and ultrasonic velocity (2 MHz) of pure solvents: ethanol, MEK and DMF, and BCFA solutions (0.5–4 wt%) were investigated at three different temperatures: 30, 35 and 40 °C. Various acoustical parameters such as isentropic compressibility ( κ s ), internal pressure ( π ), free volume ( V f ), free path length ( L f ) and Solvation Number ( S n ) were determined and correlated with concentration ( C ). Fairly good to excellent linear relationships are observed at three temperatures. The linear decrease of κ s , π and L f with C and linear increase with temperature; and linear increase of V f with C and T in DMF system, nonlinear increase with C and T in EtOH system and nonlinear decrease with C and increase with T in MEK system indicated strong molecular interactions in the solutions and solvophilic nature of BCFA, which is further supported by positive values of Solvation Number. The observed Solvation trend is EtOH > MEK > DMF.

  • STUDIES ON ACOUSTICAL PROPERTIES OF POLY(4,4′-CYCLOPENTYLIDENE DIPHENYLENE TOLUENE-2,4-DISULFONATE) IN DIFFERENT SOLVENTS AT 30°C
    European Polymer Journal, 1997
    Co-Authors: K.m Rajkotia, Shipra Baluja, P. H. Parsania
    Abstract:

    Abstract Various acoustical parameters of poly(4,4′-cyclopentylidene diphenylene toluene-2,4-disulfonate) (PSBPT) in chloroform, 1,2-dichloroethane, 1,4-dioxane and tetrahydrofuran were evaluated at 30°C using an interferometer operating at a frequency of 3 MHz. Some of these parameters, except the internal pressure, relaxation time, classical absorption coefficient and Solvation Number, were correlated with concentration. Excellent linear correlations between the parameters U , Z , K s , R , b , L f and r and concentration are observed. The increase of U , Z , R , b , P and decrease of K s , r and L f with increasing solute concentration C indicated polymer-solvent interaction. The positive values of the Solvation Number further supported the structure forming tendency of PSBPT. The relative viscosity against C plots indicated structural changes take place after 1% concentration except for the tetrahydrofuran system where it is observed at about 2% concentration; due to polymer-polymer entanglement. © 1997 Elsevier Science Ltd