Dielectric properties of some cadmium and mercury amino alcohol complexes at low temperatures (original) (raw)
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Dielectric spectroscopy of some heteronuclear amino alcohol complexes
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2006
The temperature dependent dielectric spectroscopic properties of two heteronuclear complexes of monoethanolamine (MEA) at a wide temperature range (303-413 K) were investigated by impedance spectroscopy, in the frequency range from 100 Hz to 100 kHz. The frequency dependence of the impedance spectra plotted in the complex plane shows semi-circles. The Cole-Cole diagrams have been used to determine the molecular relaxation time, τ. The temperature dependence of τ is expressed by thermally activated process. Relaxation frequencies corresponding to the rotation of the molecules about their long axes are expected to lie above 10 MHz and exhibit Arrhenius behavior, where a single slope is observed with activation energy values equal to 0.67 and 0.78 eV. The ac conductivity σ ac (ω) is found to vary as ω s with the index s ≤ 1, indicating a dominant hopping process at low temperatures. The dielectric permittivity dependence as a function of frequency and temperature have been determined and showed a strong dispersion at frequency lower than 10 kHz. Capacitance and losses, tan δ, decreased with increasing frequency and increased with increasing temperature. The analysis of the data reveals that such characteristics are in good agreement with semi-conducting features based mainly on the hopping mechanism.
Dielectric studies of H-bonded complexes of benzamide and nicotinamide with alcohols
Indian Journal of Pure & Applied Physics, 2006
The hydrogen-bonded complexes formed by benzamide and nicotinamide with alcohols in 1, 4-dioxan were studied at 303 K. The following alcohols were used: 2-butoxy ethanol, 2-ethyl hexanol, hexan-1-ol and isopropanol. The dipole moments of the complexes were determined using Huyskens method. The excess dipole moments of the complexes were obtained from bond angle data. The results show the domination of polarization effects and the non-feasibility of higher order complexations.
Dielectric Relaxation Studies of Decanol Complexes with Amines using Time Domain Reflectometry
The dielectric relaxation studies for decanol-amine mixtures over the frequency range of 10 MHz – 10 GHz have been carried out using pico-second time domain reflectometry technique. The dielectric quantities like the static dielectric constant (ε0m) and the dielectric constants at infinite frequency (ε∞m) were obtained. The relaxation time (τ), the effective Kirkwood correlation factor (geff), the excess dielectric parameter such as excess dielectric permittivity (ε E) and excess inverse relaxation time (1/τ) E were calculated. The thermodynamic properties (Fτ) of the mixtures of decanol with diethyl amine, n-butylamine, triethylamine, aniline and pyridine were evaluated. The Bruggeman factor shows large variation with volume fraction of aromatic amines. The (geff) is almost unity for amines and > 1 for decanol with diethylamine, triethylamine, aniline and pyridine mixtures, showing a parallel orientation of the dipoles. The studies suggest that these amines effectively break the -clusters of decanol and form specific complexes without any charge transfer. It is observed that the values of the enthalpy of activation (Fτ) for the dielectric relaxation always greater than the theoretically predicted values for all the mixtures studied.
Dielectric spectroscopy of organic solvents ofvarying polarity
2016
The dielectric constant and the conductivity for several organic solvents of varying polarity and for colloidal suspensions are measured using dielectric spectroscopy as a function of frequency, over the frequency range 0.1 Hz to 100 kHz. These measurements are carried out for organic solvents of different polarities: cyclohexyl bromide (CHB), castor oil, cis+trans-decahydronaphtalene (decalin) and decane. In addition, dielectric spectroscopy is carried out for polymethylmethacrylate (PMMA) colloidal spheres in the intermediate polar mixture of cyclohexy bromide (C 6 H 11 Br,(CHB)) and 20% cis+trans-decalin by volume. The primary result in this thesis is the examination of electrode polarization effects, which were observed at low frequency in CHB and CHB-decalin mixtures. A
Journal of King Saud University - Science, 2012
Dielectric and conductivity properties of cobalt(II), nickel(II), and copper(II)-imidazole-2-carboxaldehyde-glycylglycine (imal-glygly) complexes have been studied using impedance spectroscopy. The dielectric constant and dielectric loss factor for metal complexes have been analyzed in the frequency range from 1 Hz to 1 MHz at room temperature. The a.c. conductivity result reveals that these complexes exhibit dissimilar frequency dependent conductivity. An attempt has been made to investigate the relaxation and conductivity studies, since there are fairly few literatures available.
Indian Journal of Physics, 2012
The mechanism of dipolar complexation involving TBP and three alcohols namely 1-hexanol, 1-heptanol and 1-octanol in an apolar medium benzene is investigated by three direct methods using dielectric measurement data at frequency 455 kHz and at temperature 303.16 K. The parameters evaluated in these systems are the interaction dipole moment, induced polarization and apparent complex formation constant for thermodynamically most favoured stoichi-ometry of 1:1 complexes. Two conclusions resulted from the study. Firstly, the complexation is predominantly due to polarization effect involving charge redistribution and secondly, the complex formation is most favoured in 1-hexanol system.
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2023
The dielectric behaviour and molecular structure of metal complexes Cu(II),Ni(II) and UO 2 ((VI) of the ligand oxaloanilic acid hydrazine have been investigated using Time Domain Reflectometry (TDR) technique in the frequency range 10 MHz to 10GHz. Cole-Davidson model has been applied for fitting the complex permittivity spectra [ ε * (ω)]. The parameters ε s-the static permittivity, τ-the dielectric relaxation time are evaluated at different temperatures from 288 0 K to 333 0 K and are discussed in respect of their molecular structural behaviours. The thermodynamic parameters, such as ΔH *-molar enthalpy, ΔS *-the molar entropy are obtained using Eyring.s rate equation. In the light of such data the possible structures of the present complexes are discussed.
Dielectric Studies on PVA±NH4SCN Complexes
The dielectric behaviour of polyvinyl alcohol (PVA) films complexed with ammonium thiocyanate (NH4SCN) have been investigated at various frequencies (from 100 Hz to 10 kHz) in the temperature range from 303 to 383 K. The relative permittivity (e0), loss tangent (tan d) and relaxation time (t) were found to be temperature and dopant concentration dependent. The experimental results reveal a, ab and b-types of relaxation processes for PVA±NH4SCN complexes.
Dielectric Properties of an Electrolyte Solution at Low Reduced Temperature
Journal of Physical Chemistry B, 1999
We report on the complex dielectric permittivity up to 20 GHz of solutions of tetrabutylammonium bromide in carbon tetrachloride at salt concentrations between 0.01 and 1 mol dm -3 , where the molar conductance increases with concentration up to molten saltlike conductances. At concentrations below about 0.1 mol dm -3 , the frequency dependence of the permittivity shows Debye behavior with a single relaxation time, as would be expected for the reorientation of dipolar ion pairs. The static permittivity monotonically increases with concentration. Assuming dipolar processes as the major contributors to the dielectric spectra, Kirkwood's theory yields correlation factors which rapidly decrease with increasing salt concentration, indicating strong antiparallel correlations of dipole orientations even at concentrations as low as c ) 10 -4 mol dm -3 . Above c ) 0.1 mol dm -3 the spectra broaden rapidly, while the viscosity remains low. In this range the spectra are well-represented by a Cole-Cole expression with a mean relaxation time essentially proportional to the viscosity. We suggest that at higher concentrations part of the polarization arises from a Debye-Falkenhagentype mechanism caused by the asymmetry of the ion atmosphere in the applied field. The increasing importance of this contribution appears to result from the dissociation of ion pairs by interaction with the remainder of the screening ionic fluid, which eventually leads to a transition to molten saltlike structures.