Thermal and optical properties of benzofuran-2-yl 3-phenyl-3-methylcyclobutyl thiosemicarbazone M. Koca a , F. Dagdelen b , Y. Aydogdu b, * a Department of Chemistry, Faculty of Arts and Sciences, Firat University, Elazig, Turkey b Department of Physics, Faculty of Arts and Sciences, Firat University, Elazig, Turkey Received 6 March 2004; received in revised form 4 May 2004; accepted 15 May 2004 Available online 21 June 2004 Abstract The thermal degradation of the benzofuran-2-yl 3-phenyl-3-methylcyclobutyl thiosemicarbazone (CBSC) was studied under air atmosphere using DSC and simultaneous TG/DTA at the temperature range 20– 500 jC. Thermal melting activation energy which are 308.6 and 307.9 kJ/mol were evaluated using Kissinger method from DSC and DTA curves, respectively. The activation energy of thermal decomposition was calculated using the Ozawa method for two decomposition stages. The experimental results showed that the activation energy of decomposition for non-isothermal behavior are 123.8 and 135.2 kJ/mol for the first (at 5% weight loss) and second (at 20% weight loss) decomposition stages, respectively. By using hot probe method, electrical conduction mechanism of CBSC was found as p-type. The values of thermal activation energy of electrical conduction, E 1 and E 2 , as calculated from lnr = f (1000/T ) curves, were found to be 3.90 and 0.36 eV, respectively. Optical absorption studies in the wavelength range 190–900 nm showed that direct optical band gap of the benzofuran- 2-yl 3-phenyl-3-methylcyclobutyl thiosemicarbazone is 2.80 eV. D 2004 Elsevier B.V. All rights reserved. Keywords: Thermal activation energy; Optical band gap; Benzofuran; Cyclobutane 1. Introduction In recent years, the investigations on the electrical conduction mechanism in organic compounds have been much intensified [1]. This is mainly due to attracting properties of organic semiconductors for the technology of solid state devices [1–4]. Electrically conducting and semi- conducting organic compounds have been a subject of extensive studies in view of both academic interest and potential technological applications [5]. Organic semicon- ductors can conduct charges due to partial delocalization or charge hopping through the molecules [6,7]. A number of organic-based PV cells, including organic/inorganic hybrid configurations, have been investigated [8–10]. Recently, the study on the thermal properties of heterocyclic compounds is attracting amount of researchers due to the compounds’ compact and stable structure [11]. In this the paper, the thermal melting and thermal decomposition activation energies, electrical conductivity, optical band gap of benzofuran-2-yl 3-phenyl-3-methylcy- clobutyl thiosemicarbazone (CBSC) were investigated. 2. Experimental procedure 2.1. The synthesis of benzofuran-2-yl 3-phenyl-3-methyl- cyclobutyl thiosemicarbazone In the light of the above observation, we have selected 1- aryl-1-methyl-3-(2-chloro-1-oxoethyl cyclobutane as the starting compound, which were synthesized according to the literature procedure published previously [12]; 10 mmol (2.225 g) of 1-phenyl-1-methyl-3-(2-cloro-1-oxoethyl) cyclobutane, 15 mmol (2.07 g) K 2 CO 3 and 11 mmol (1.342 g) salicylic aldehyde were stirred in 100 ml of acetonitrile and were refluxed for 8 h. The mixture was cooled, filtrated and the solvent was evaporated. It was washed a few times. Then, it was crystallized in ethanol. And then, a mixture of ketone 1.933 g (6.7 mmol), 0.6075 g (6.7 mmol) thiosemicarbazide, 0.01 mg p-toluene sulfonic acid monohydrate in absolute ethanol (100 ml) was refluxed 0167-577X/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2004.05.016 * Corresponding author. Fax: +90-424-2330062. E-mail address: yaydogdu@firat.edu.tr (Y. Aydogdu). www.elsevier.com/locate/matlet Materials Letters 58 (2004) 2901 – 2905