6 Molecular Magnetism of Metal Complexes and Light-Induced …
303
such as ground and excited spin states, magnetic anisotropy, and QTM. No Mössbauer study has been reported for [Mn 12 ] ac because of less applicability for Mn
atoms. A one-electron reduced analog, [Fe(C 5 H 5 ) 2 ][Mn 12 O 12 (O 2 CC 6 F 5 ) 16 (H 2 O) 4 ]
(Fe(C 5 H 5 ) 2 = ferrocenium cation), was reported by Kuroda et al. [59] to determine
the relaxation of magnetization derived from the magnetic field of the [Mn 12 ]
− core
via
57 Fe Mössbuaer spectra of the ferrocenium site. The complex showed the effective
energy barrier (U eff ) of magnetization reversal estimated as 50 K. In
57 Fe Mössbauer
spectra (Fig. 6.37) below 13.5 K, a broad magnetic hyperfine splitting was found,
which is a proof of slow paramagnetic relaxation originating in the SMM behavior
of the [Mn 12 ]
− unit.
The [Fe 4 ] [60, 61] and [Fe 8 ] [60, 62, 63] coordination clusters are representative SMMs, the chemical formulae of which represent as [Fe 4 (OCH 3 ) 6 (dpm) 6 ]
(Hdpm = dipivaloylmethane) and [Fe 8 O 2 (OH) 12 (tacn) 6 ]Br 8 (Fig. 6.38; tacn = 1,4,7Fig. 6.37 Temperature-varied 57 Fe Mössbauer spectra of 11% 57 Fe-enriched
[Fe(C 5 H 5 ) 2 ][Mn 12 O 12 (O 2 CC 6 F 5 ) 16 (H 2 O) 4 ] sample [59]. Reprinted with permission from
[59]. Copyright 2001 American Chemical Society
303
such as ground and excited spin states, magnetic anisotropy, and QTM. No Mössbauer study has been reported for [Mn 12 ] ac because of less applicability for Mn
atoms. A one-electron reduced analog, [Fe(C 5 H 5 ) 2 ][Mn 12 O 12 (O 2 CC 6 F 5 ) 16 (H 2 O) 4 ]
(Fe(C 5 H 5 ) 2 = ferrocenium cation), was reported by Kuroda et al. [59] to determine
the relaxation of magnetization derived from the magnetic field of the [Mn 12 ]
− core
via
57 Fe Mössbuaer spectra of the ferrocenium site. The complex showed the effective
energy barrier (U eff ) of magnetization reversal estimated as 50 K. In
57 Fe Mössbauer
spectra (Fig. 6.37) below 13.5 K, a broad magnetic hyperfine splitting was found,
which is a proof of slow paramagnetic relaxation originating in the SMM behavior
of the [Mn 12 ]
− unit.
The [Fe 4 ] [60, 61] and [Fe 8 ] [60, 62, 63] coordination clusters are representative SMMs, the chemical formulae of which represent as [Fe 4 (OCH 3 ) 6 (dpm) 6 ]
(Hdpm = dipivaloylmethane) and [Fe 8 O 2 (OH) 12 (tacn) 6 ]Br 8 (Fig. 6.38; tacn = 1,4,7Fig. 6.37 Temperature-varied 57 Fe Mössbauer spectra of 11% 57 Fe-enriched
[Fe(C 5 H 5 ) 2 ][Mn 12 O 12 (O 2 CC 6 F 5 ) 16 (H 2 O) 4 ] sample [59]. Reprinted with permission from
[59]. Copyright 2001 American Chemical Society