期刊
INORGANIC CHEMISTRY
卷 44, 期 5, 页码 1221-1229出版社
AMER CHEMICAL SOC
DOI: 10.1021/ic048765l
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资金
- NCRR NIH HHS [RR-01209] Funding Source: Medline
- NIGMS NIH HHS [GM50730] Funding Source: Medline
Select ferrous spin-transition complexes with the pentadentate ligand 2,6-bis(bis(2-pyridyl)methoxymethane)pyridine (PY5) were examined using variable-temperature solution solid-state magnetic susceptibility, crystallography, X-ray absorption spectroscopy (XAS), and UV/vis absorption spectroscopy. Altering the single exogeneous ligand, X, of (Fe(PY5)(X)(n+) is sufficient to change the spin-state of the complexes. When X is the weak-field ligand Cl-, the resultant Fe complex is high-spin from 4 to 300 K, whereas the stronger-field ligand MeCN generates a low-spin complex over this temperature range. With intermediate-strength exogenous ligands (X = N-3(-), MeOH), the complexes undergo a spin-transition. [Fe(PY5)(N-3)](+), as a crystalline solid, transitions gradually from a high-spin to a low-spin complex as the temperature is decreased, as evidenced by X-ray crystallography and solid-state magnetic susceptibility measurements. The spin-transition is also evident from changes in the pre-edge and EXAFS regions of the XAS Fe K-edge spectra on a ground crystalline sample. The spin-transition observed with [Fe(PY5)(MeOH)](2+) appears abrupt by solid-state magnetic susceptibility measurements, but gradual by XAS analysis, differences attributed to sample preparation. This research highlights the strengths of XAS in determining the electronic and geometric structure of such spin-transition complexes and underscores the importance of identical sample preparation in the investigation of these physical properties.
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