| Research Abstract |
We have concentrated ourselves on the molecular strain of Fe (II) complex compounds throughout this project. While we started from anomalous magnetic properties of such strained complexes, larger portion is devoted to the ligand exchange and solid-state synthesis of those complexes. All the solid-state reactions in the latter category are the consequences of molecular strain. Main results are correspondingly divided into two parts, I.e,
(A) Change in the magnetic properties due to molecular strain, and
(B) Ligand exchange reaction as a consequence of disproportionation of metal-ligand coordination bonds.
The category (A) is attributed to the change from the low spin (ィイD11ィエD1AィイD21gィエD2) to high spin (ィイD15ィエD15TィイD22gィエD2) state. The spin crossover temperature lowers while a metastabe high spin state at temperatures as low as 10K appears simultaneously. These are explained by the change in the distribution of electron energy states induced by the molecular strain and related loss of lig
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and field symmetry.
We then proceeded to the chemical consequences of loss of the ligand field symmetry. Disproportionation of the coordination bonds between Fe (II) and the ligands inevitably results in the attack of any chemical species, as counter ions, as solvents or as an independently dissolved organic molecules, which are capable to form coordination bonds with Fe (II). Examples of ligand exchange in its narrow definition are: formation of [Fe(bpy)(phen) ィイD22ィエD2](NCS) ィイD22ィエD2, [Fe(bpy)ィイD22ィエD2(phen)] (NCS) ィイD22ィエD2, [Fe(phen)ィイD23ィエD2](NCS) ィイD22ィエD2 from a mixture of [Fe(bpy) ィイD23ィエD2](NCS)ィイD22ィエD2(bpy=2,2'-bipyridine) and phen (1,10-phenanthroline) by simple milling in a planetary mill.
We further succeeded direct solid-state synthesis of [Fe(phen)ィイD23ィエD2] ClィイD22ィエD2 by milling a mixture of FeClィイD22ィエD2・4HィイD22ィエD2O and phen. We confirmed the disproportionation of coordination bonds between Fe (II) and four HィイD22ィエD2O molecules as 1igands by different spectroscopies. Finally, we concluded that the deletion of the weakest HィイD22ィエD2O is immediately followed by the new coordination bonding with phen. By the same token, preliminary milling of FeClィイD22ィエD2・4HィイD22ィエD2O alone turned out to accelerate rate of [Fe(phen) ィイD23ィエD2] ClィイD22ィエD2 formation. Less
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