Spectrochimica Acta Part A 65 (2006) 127–132 Dielectric spectroscopy of some heteronuclear amino alcohol complexes Mamdouh S. Masoud a , Medhat A. Shaker b , Alaa E. Ali b,∗ a Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt b Physics and Chemistry Department, Faculty of Education, Damanhour, Alexandria University, Egypt Received 24 July 2005; accepted 15 September 2005 Abstract The temperature dependent dielectric spectroscopic properties of two heteronuclear complexes of monoethanolamine (MEA) at a wide tempera- ture 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. © 2005 Elsevier B.V. All rights reserved. Keywords: Amino alcohol complexes; Dielectric properties; Permittivity and loss; Dielectric relaxation; Arrhenius plot 1. Introduction Ethanolamines are versatile ligands containing amine and alcohol groups that readily form coordination compounds with almost all metal ions and behave as N- and O-donor ligands. Their structural chemistry has been investigated in depth using different spectroscopic and thermal techniques. Their bifunc- tional nature enables them to serve a variety of commercial appli- cations such as corrosion inhibitors, surfactants, gas purification and herbicides [1]. Recently, aqueous ethanolamines remain as the principal acid gas absorbents and comprise 40% of the mar- ket [2]. Homo- and hetero-bimetallic ethanolaminate derivatives of a number of metals have been reported recently [3–5]. Dielec- tric spectroscopy (DS) is an old experimental tool, which has dramatically developed in the last two decades. It covers nowa- days the extraordinary spectral range from 10 -6 to 10 12 Hz. This enables researchers to make sound contributions to contempo- rary problems in modern physics. The complex dielectric func- tion describes the interaction of electromagnetic waves with mat- ∗ Corresponding author. E-mail address: dralaae@yahoo.com (A.E. Ali). ter and reflects by that the underlying molecular mechanisms. It is known that dielectric study can reveal many information of a solid, such as phase transition, defect, and transport properties. A detailed analysis of the frequency and temperature dependence of the ac conductivity and permittivity is necessary in order to characterize the microscopic mechanisms and the accompanied relaxation phenomena of the charge carrier transport. Dielectric spectroscopy is a non-invasive, very sensitive technique to inves- tigate complex systems in general and is particularly suitable to study biological systems as recently reviewed [6–10]. For the investigation of relaxation processes and conductivity dielectric spectroscopy is a frequently used method. Dielectric relaxation spectroscopy (DRS) is a popular and powerful technique that has been shown to provide information about the molecular dynamics of almost any kind of materials and liquid crys- tals [11,12]. In particular, dielectric measurements complement dynamic mechanical analysis (DMA), for example, by deter- mining the frequency dependence of the various processes over a wider range of frequencies. As a part of our ongoing research on the synthesis, spectral, thermal and structural analysis of mono-, di- and triethanolamine complexes with of most classes of metals [13–23], we report in this paper the dielectric prop- erties of the CoNi(MEA) 2 Cl 2 ·H 2 O and CoCu 2 (MEA) 2 Cl 4 ·H 2 O 1386-1425/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2005.09.036