Dielectrical, conduction mechanism and thermal properties of rhodanine azodyes
Dielectrical, conduction mechanism and thermal properties of rhodanine azodyes
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DOI：
10.1016/j.mssp.2013.12.005
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发表时间：
2014-03
影响因子：
4.1
通讯作者：
N. El-Ghamaz;A. El-Sonbati;M. Diab;A. El‐Bindary;M. Awad;Sh.M. Morgan
中科院分区：
文献类型：
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作者：
N. El-Ghamaz;A. El-Sonbati;M. Diab;A. El‐Bindary;M. Awad;Sh.M. Morgan
本文报道了5-（4 '-衍生物苯基偶氮）-2-硫代噻唑烷-4-酮（HLn）（n=1，R= OCH_3;n=2，R= CH_3;n=3，R=H; n =4，R= NO_2）在46-800 ℃范围内的差示扫描量热分析（DSC）和热重分析（TGA）。HL_1、HL_3和HL_4的热分解活化能在59.10-299.72 kJ/mol之间。利用量子化学计算研究了所研究的化合物（HLn）的分子和电子结构。在频率0.1-100 kHz和温度303-500 K范围内研究了HLn的交流电导率（σac）和介电性能。研究了真实的和虚部介电常数的温度和频率依赖性。在不同频率下计算了所研究的衍生物的热活化能值。所有配体的电导率热活化能Δ E1和Δ E2随测试频率的增加而减小。活化能Δ E1和ΔE2按p-（NO2>H> CH 3> OCH 3）的顺序增加。这与Hammett取代基系数（σR）的预期结果一致。电导率被发现是依赖于化合物的结构。σ ac的值与频率相关，公式为σacα ω S，其中指数S的行为决定了工作传导机制。相关势垒跳跃（CBH）是HLn的主要导电机制。计算了最大势垒高度（Wm）。
In this paper, we report on the differential scanning calorimetry analysis (DSC) and thermogravimetric analysis (TGA) performed for 5-(4'-derivatives phenylazo)-2-thioxothiazolidin-4-one (HLn) (n=1,R=OCH3;n=2,R=CH3;n=3,R=H; andn=4,R=NO2) in the temperature range 46–800 °C. The values of the thermal activation energies of decomposition of HL1, HL3and HL4are found in the range 59.10–299.72 kJ/mol. The molecular and electronic structures of the investigated compounds (HLn) were also studied using quantum chemical calculations. The alternating current conductivity (σac) and dielectrical properties of HLnwere investigated in the frequency range 0.1–100 kHz and temperature range 303–500 K. The temperature and frequency dependence of the real and the imaginary dielectrical constants are studied. The values of the thermal activation energy for derivatives under investigation were calculated at different frequencies. The values of thermal activation energies of electrical conductivity ΔE1and ΔE2for all ligands decrease with increasing the test frequency. The activation energies, ΔE1and ΔE2, increase according to the following orderp-(NO2>H>CH3>OCH3). This is in accordance with that expected from Hammett's substituent coefficients (σR). The conductivities are found to be dependent on the structure of the compounds. The values ofσacare related to the frequency asσacα ωSwhere the behavior of the exponentSdetermines the operating conduction mechanism. The correlated barrier hopping (CBH) is the dominant conduction mechanism for HLn. The values of maximum barrier height (Wm) were calculated.