Crystal structure, thermal behavior and electric properties of a new semiconductor cobalt-based hybrid material

The crystals of the new organic-inorganic hybrid material, (C5H12N)2[CoBr2.73Cl1.27], were successfully synthesized by the slow evaporation method and characterized by single-crystal X-ray diffraction, thermal analysis, UV-Vis absorption and electrical measurements. This compound crystallizes in the centrosymmetric space group P21/n of the monoclinic system with unit cell parameters: a = 9.7724 (6) angstrom, b = 12.3920 (6) angstrom, c = 15.0307 (9) angstrom, beta = 100.864(6) degrees, V = 1787.59(18) angstrom 3 and Z = 4. The IR spectrum of the compound is studied, especially for the cationic vibrational part. The thermal analysis indicates that (C5H12N)2[CoBr2.73Cl1.27] is stable up to 270 degrees C and that it undergoes two reversible phase transitions at 152 and 187 degrees C and at 141 and 128 degrees C on heating and cooling, respectively. From UV visible gap energy value of 3 eV it can be concluded that the new mixed halide compound is a semiconductor material. The electrical behavior of (C5H12N)2[CoBr2.73Cl1.27] was studied using impedance spectroscopy in the temperature range of 323 to 403 K. According to a study on the frequency dependence of ac conductivity, the material follows Jonscher's universal dynamic law with an increase in the frequency exponent (s) as temperature increases. This behavior reveals that the conduction mechanism is the nonoverlapping small polaron tunneling (NSPT) model.