Infrared Electroabsorption Spectroscopic Study of Association Structures of 5CB in the Solution, Isotropic Liquid and Nematic Liquid Crystal States

Min, Young; Hiramatsu, Hirotsugu; Hamaguchi, Hiro O.

doi:10.1246/cl.2002.68

Cited by 6 publications

(7 citation statements)

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“…Thus, the orientational polarization emerges as the zeroth-derivative contribution in eq . In previous studies on room-temperature liquids and solutions, ,,, the zeroth-derivative term has proven dominant. The remaining first- and second-derivative contributions to the Δ A signal are responsible for the frequency shift and band broadening due to the Stark effect.…”

Section: Methodsmentioning

confidence: 96%

Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C₂Cl₄: Solvation of the Solute and Self-Association of Acetonitrile

Wang

Shigeto

2011

J. Phys. Chem. A

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Solvated structures of N,N-dimethyl-p-nitroaniline (DMPNA), an analog of p-nitroaniline (PNA), and self-associated structures of acetonitrile (ACN) in mixed solvents of ACN and C(2)Cl(4) were studied using infrared (IR) electroabsorption and FTIR spectroscopies. IR electroabsorption spectroscopy measures changes in IR absorption intensity upon application of external electric field modulation, which are a sensitive probe for permanent dipole moments. In ACN/CCl(4), PNA has been shown to occur as two distinct solvated forms, namely, 1:1 and 1:2 forms, which have one and two ACN molecule(s), respectively, associated with PNA. The IR electroabsorption and FTIR measurements on DMPNA show that, unlike PNA, DMPNA occurs as a monomer in ACN/C(2)Cl(4) rather than as specific solvated structures analogous to the 1:1 and 1:2 forms because of the substitution effect. Not only does the N,N-dimethyl substitution in DMPNA hamper solvation of ACN at the N(CH(3))(2) group, but it also indirectly blocks strong interactions with ACN at the NO(2) group. Furthermore, by using the ΔA signal of DMPNA as an internal intensity standard, it was found that the dipole moment of ACN in the DMPNA/ACN/C(2)Cl(4) system is about 1.5 times larger than that of the ACN monomer in dilute CCl(4) solution. This large value of the dipole moment in the solution studied here is attributable to the formation of a head-to-tail linear dimer of ACN, whereas the antiparallel dimer is energetically more favorable in the gas phase.

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Section: Methodsmentioning

confidence: 96%

Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C₂Cl₄: Solvation of the Solute and Self-Association of Acetonitrile

Wang

Shigeto

2011

J. Phys. Chem. A

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“…The orientational-change signal in the IR EA difference (ΔA) spectrum is a function of the permanent dipole moment (μ P ), the angle η between μ P and the transition dipole moment (μ T ) of each vibrational mode (defined at 0°−180°). 35 The analysis of (μ P , η) with the orientation change signal has been applied to identify the monomeric and dimeric forms of Nmethylacetamide, 36 the multiple solvation structure of pnitroaniline, 37 H 2 O in an organic solvent 38 or at the core and shell of a reverse micelle, 39 or the response of liquid crystal (5CB) 40 to the applied electric field. Also, the external electric field affects the molecular structure, and consequently, the fraction of tautomers in equilibrium.…”

Section: ■ Introductionmentioning

confidence: 99%

Tautomer Structures in Ketose–Aldose Transformation of 1,3-Dihydroxyacetone Studied by Infrared Electroabsorption Spectroscopy

Chen

Hiramatsu

2019

J. Phys. Chem. B

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The acyclic form of monosaccharides exists in a structural equilibrium, with aldose having the aldehyde group and ketose the ketone group (ketose−aldose equilibrium). A basic catalyst facilitates their transformation, which affects the chemical properties of the monosaccharide. In this study, we investigated the ketose−aldose transformation of 1,3-dihydroxyacetone (1,3-DHA), one of the simplest systems of the ketose−aldose equilibrium. We examined the effects of piperidine as the basic catalyst and used IR electroabsorption spectroscopy to study the responses to an external electric field. We analyzed the changes in IR absorption by considering the changes in the molecular orientation and number of molecules in response to the external electric field. The results of the analysis revealed the permanent dipole moment μ P , an angle η between μ P and μ T (the transition moment of the molecular vibration), and the equilibrium constants. The ketose−aldose transformation of 1,3-DHA can be explained in terms of the equilibrium of three states. In the presence of piperidine, a five-state equilibrium was concluded. On the basis of the experimental data, we propose plausible models of dihydroxyacetone, E-enediols, Z-enediol, or glyceraldehyde for each state. The results of our structural analysis of these tautomers provide a detailed understanding of the ketose−aldose transformation of acyclic saccharides and the effects of the basic catalyst.

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“…Despite these obvious advantages, there have been only a few reports on the infrared electroabsorption spectroscopy of m olecules, presumably because of the experimental dif culty in detecting extremely small signals with low-sensitivity infrared detectors. In fact, there are a number of infrared electroabsorption spectroscopic studies of liquid crystals 4,[13][14][15] for which large signals due to the reorientation of domains are detected without m uch dif culty. To the best of our knowledge, the rst infrared electroabsorption spectroscopy looking at the molecular response was reported by Handler and Aspnes in 1967.…”

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confidence: 99%

Development of Infrared Electroabsorption Spectroscopy and its Application to Molecular Structural Studies

Hiramatsu

Hamaguchi

2004

Appl Spectrosc

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We have constructed an infrared electroabsorption spectroscopic system employing the alternating current (AC) coupled dispersive method developed previously in our laboratory. It is highly sensitive, measuring electric-field-induced infrared absorption changes as small as 6 x 10(-8) in the mid-infrared region of 4000-820 cm(-1). Infrared electroabsorption spectra of liquids and solutions can be measured at room temperature. The system was first applied to liquid acetone to observe the orientational as well as the electronic polarization signals. These signals show distinct behaviors that are exactly predicted by theory. It was then applied to liquid 1,2-dichloroethane, for which electric-field-induced gauche/trans equilibrium changes were detected as infrared absorption changes. The gauche/trans ratio in room-temperature liquid 1,2-dichloroethane has been determined for the first time as 1.4 +/- 0.2. This equilibrium constant has led to the free energy difference deltaG of 0.9 +/- 0.4 kJ mol(-1) (deltaG = G(g) - G(t)) and the entropy difference of deltaS = -3.0 +/- 1.4 J K(-1) mol(-1) with the known enthalpy difference deltaH approximately 0.0 kJ mol(-1). Finally, the system was applied to 1,4-dioxane solutions of N-methylacetamide. The dipole moments of the monomer as well as that of the dimer of N-methylacetamide have been determined separately and a head-to-tail structure of the dimer has been clarified. The instrumentation and the theoretical basis of infrared electroabsorption spectroscopy are described in detail together with the above-mentioned experimental results.

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Infrared Electroabsorption Spectroscopic Study of Association Structures of 5CB in the Solution, Isotropic Liquid and Nematic Liquid Crystal States

Cited by 6 publications

References 6 publications

Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C₂Cl₄: Solvation of the Solute and Self-Association of Acetonitrile

Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C₂Cl₄: Solvation of the Solute and Self-Association of Acetonitrile

Tautomer Structures in Ketose–Aldose Transformation of 1,3-Dihydroxyacetone Studied by Infrared Electroabsorption Spectroscopy

Development of Infrared Electroabsorption Spectroscopy and its Application to Molecular Structural Studies

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Infrared Electroabsorption Spectroscopic Study of Association Structures of 5CB in the Solution, Isotropic Liquid and Nematic Liquid Crystal States

Cited by 6 publications

References 6 publications

Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C2Cl4: Solvation of the Solute and Self-Association of Acetonitrile

Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C2Cl4: Solvation of the Solute and Self-Association of Acetonitrile

Tautomer Structures in Ketose–Aldose Transformation of 1,3-Dihydroxyacetone Studied by Infrared Electroabsorption Spectroscopy

Development of Infrared Electroabsorption Spectroscopy and its Application to Molecular Structural Studies

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Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C₂Cl₄: Solvation of the Solute and Self-Association of Acetonitrile

Infrared Electroabsorption Spectroscopy of N,N-Dimethyl-p-nitroaniline in Acetonitrile/C₂Cl₄: Solvation of the Solute and Self-Association of Acetonitrile