202192-54-9Relevant academic research and scientific papers
Raman signature of the Fe2O2 'diamond' core
Wilkinson, Elizabeth C.
, p. 955 - 962 (1998)
We report the resonance Raman (RR) spectra of iron complexes containing the Fe2(μ-O)2 core. Frozen CH3CN solutions of the Fe(III)Fe(IV) intermediate [Fe2(μ-O)2L2](ClO4)3 (where L = TPA, 5-Me3-TPA, 5-Me2-TPA, 5-MeTPA, 5-Et3-TPA, or 3-Me3-TPA) show numerous resonance-enhanced vibrations, and among these, an oxygen-isotope-sensitive vibration around 667 cm-1 that shifts ca. 30 cm-1 when the samples are allowed to exchange with 18OH2, and whose Raman shift does not vary with methyl substitution of the TPA ligand. Spectra of iron-isotope-substituted samples of [Fe2(μ-O)2(L)2](ClO4)3 (54Fe and 57Fe for L = TPA, and 54Fe and 58Fe for L = 5-Me3-TPA) show that this vibration is also iron-isotope-sensitive. These isotopic data taken together strongly suggest that this vibration involves motion of the Fe2(μ-O)2 core that is isolated from motions of the ligand. A frozen CH3CN solution of the diiron(III) complex [Fe2(μ-O)2(6-Me3-TPA)2](ClO4)2 shows one intense resonance-enhanced vibration at 692 cm-1 that shifts -30 cm-1 with 18O labeling. Normal coordinate analysis of the Fe2(μ-O)2 core in [Fe2(μ-O)2(5-Me3-TPA)2](ClO4)3 supports the assignment of the Fermi doublet centered around 666.2 cm-1 as an A1 vibration of this core. Furthermore, we propose that this unique feature found in the region between 650 and 700 cm-1 is indicative of a diamond core structure and is the Raman signature of an iron cluster containing this core.
