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Anion Replacement in Preparation of Spin-crossover Iron(II) Complexes 1.Inorganic and Physical Chemistry Division, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jl. Ganesha No. 10, Bandung 40132 Indonesia. Abstract The spin crossover (SCO) phenomenon is an attractive magnetic property for the development of inorganic smart materials, such as molecular sensors dan memory devices. One of the inorganic compounds that have been widely studied its SCO properties is the iron(II) complexes, due to the 3d electrons of iron(II) being able to change from high spin state (HS, paramagetic) to low spin state (LS, diamagnetic) or vice versa. The energy difference between the HS and LS states is on the order of the magnitude of the thermal energy kT. These changes can occur due to external influences such as temperature, light irradiation, and pressure. The SCO phenomenon is mainly influenced by moderate ligand field strength, as found in triazole derivatives ligands. In addition, counter anions in the iron(II) complexes also significantly contribute to the physical characteristic of SCO in terms of transition temperature and transition pattern. Here, we have prepared two SCO compounds, i.e first the [Fe(Htrz)3](CF3CO2)2 complex (Htrz is 4-H 1,2,4-triazole) was synthesized form [Fe(Htrz)3]SO4 complex in which the sulfate anion replaced by tetrafluoroacetate from its Barium salt. The complex [Fe(Htrz)3](CF3CO2)2 is diamagnetic violet solid and changes to white on heating. The second complex is [Fe(Atrz)3](S4O6) complex (Atrz is 4-NH2 1,2,4 triazole) that synthesized from [Fe(Atrz]Cl2 in which the chloride anion replaced by tetrathionate from its sodium salt. The [Fe(Atrz)3](S4O6) complex is a paramagnetic white solid at room temperature and changes to violet on cooling. Keywords: anion replacement, SCO, iron(II) complexes Topic: CHEMISTRY AND MATERIAL SCIENCES |
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