TRIS-4H-1,2,4-TRIAZOLE IRON(II) COMPLEX WITH TRIFLUOROACETATE (TFA) ANION

• Main Author: Laksmi Khairunisa, Elvina
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/67361
• Institution: Institut Teknologi Bandung

Tris 1,2,4-Triazole (Htrz) iron(II) complexes have been widely studied because it can have different magnetic properties when external influences such as temperature are applied. The complexes undergo a reversible transition from diamagnetic to paramagnetic when heated indicated by color changes from purple to white. This phenomenon is known as the Spin Crossover (SCO) which apart from being determined by the strength of the ligand, also depends on the type of anion. Iron(II)-Htrz complexes with halide, nitrate, tetrafluoroborate and perchlorate anions have been synthesized, but trifluoroacetate (TFA) anion has not been reported so far, except for [Fe(3bpp)2](TFA)2 (3bpp = 2,6-bis(pyrazol-3-yl)pyridine) which exhibits an incomplete transition. [Fe(Htrz)3](TFA)2 complex has been synthesized from aqueous Fe(TFA)2 solution with Htrz ligand dissolved in water produced purple-colored complex with 56 – 64% yields and has diamagnetic properties with magnetic moments in the range of 0.99 – 1.31 BM. The color change observations related to the spincrossover characteristics of the complex occurred at a half temperature value of T½? in heating mode is 76 oC and T½? in cooling mode at 66 oC. From DSC data, the transition temperature in heating mode Tc is 64.7 oC which is slightly lower compared to visual color change observation, however the entalphy and entropy values of the transition were obtained of ?H = 8.3 kJ/mol and ?S = 24.5 J/K.mol respectively. The Htrz ligand is soluble in water as well as in alcohol solvents, such as methanol, ethanol, propanol, and isopropanol, therefore in this research the similar complexes were then re-synthesized using variations of these solvents. Visually, the complexes have similar characteristics, in terms of color and magnetic properties. However, the complex prepared using ethanol solvent has very close temperature observation between visual color change T½? = 77 oC and T½? = 66 oC and transition temperature obtained from DSC data, Tc = 78.6 oC. The enthalpy and entropy values were in the same range, ?H = 9.6 kJ/mol and ?S = 27.2 J/K.mol. This complex was also syntheiszed using Microwave technique instead of magnetic heater. The result shown that the complex has a brighter color, with higher yields and shorter synthesis time