DEVELOPMENT OF SYNTHESIS AND CHARACTERIZATION OF IRON(II) COMPLEX WITH 1,2,4-TRIAZOLE LIGAND

• Main Author: Puspa Wardani, Rahmalia
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/82906
• Institution: Institut Teknologi Bandung

The octahedral iron(II) complex with the ligand 1,2,4-triazole (Htrz) is a unique compound because it is diamagnetic at low temperatures and can become paramagnetic when heated. This phenomenon occurs due to a reversible change in the electron spin in iron(II) from a low spin state to a high spin state, known as the spin transition or spin crossover (SCO) phenomenon. Synthesis of iron(II) complex compounds with Htrz ligands using water or alcohol can produce complexes with the formula [Fe(Htrz)3] 2+ or [Fe(Htrz)2(trz)]+ depending on the solvent used, synthesis technique, and precursor concentration in solution. The development of SCO complex synthesis techniques using mechanochemistry without solvents has recently been reported for iron(II) complexes with triazole derivative ligands. Synthesis of iron(II) complex with Htrz ligand and tetrafluoroborate anion (BF4 ? ) has been carried out using dissolution techniques with methanol solvent (I), etanol and water solvent (II), and without solvent (III). All synthesis techniques carried out produced products in the form of purple solids with yield percentages of 46%, 33%, and 48% for complexes (I), (II), and (III), respectively. The content of carbon, nitrogen and hydrogen elements in complexes (I) and (II) shows that the product has the formula [Fe(Htrz)2(trz)]BF4, while complex (III) is a mixture of [Fe(Htrz)2(trz)]BF4 and [Fe(Htrz)3](BF4)2. This is also supported by the presence of a peak in the Powder X-Ray Diffraction (PXRD) spectrum which corresponds to the calculated spectrum of [Fe(Htrz)2(trz)]BF4 in the low spin state. Complexes (I) and (III) begin to decompose at a temperature of around 573 K, while complex (II) begins to decompose at a temperature of around 623 K. At a temperature of 290 K the complex has a magnetic moment of 1.78 BM; 1.62 BM; and 2.05 BM for complexes (I), (II), and (III), respectively. The synthesized complex changes color to white when heated and then returns to purple when cooled, indicating the presence of the SCO phenomenon with hysteresis. Synthesis using mechanochemistry techniques provides the widest transition temperature range of 56 K with transition temperatures LS?HS = 383 K and HS?LS = 327 K