274
N. Kojima and A. Okazawa
Fig. 6.6 Spin states of the Fe III sites for [Fe III (ox) 3 ], [Fe III (dto) 3 ], and [Fe III (mto) 3 ]
tris(monothiocarbamato)iron(III) complexes, on the other hand, the rapid spin equilibrium occurs in which the HS and LS states exchange in the time scale of less
than 10
−7 s [19]. In this case, an averaged quadrupole doublet between the HS and
LS states is observed. However, the rapid spin equilibrium phenomenon has not yet
been found for assembled metal complex systems. For this viewpoint, in order to
search the rapid spin equilibrium phenomenon for assembled metal complex system
including Fe
III O 3 S 3 site, we have synthesized (C 6 H 5 ) 4 P[M
II Fe
III (mto) 3 ] (M = Mn,
Zn) consisting of the Fe
III O 3 S 3 and M
II O 6 sites and investigated the spin state of the
Fe
III O 3 S 3 site [3].
Based on the crystal structure of (n-C 3 H 7 ) 4 N[Fe
II Fe
III (dto) 3 ] analyzed by the
single-crystal X-ray diffraction [20], the Rietveld analysis was performed for the
powder X-ray diffraction pattern of (C 6 H 5 ) 4 P[Mn
II Fe
III (mto) 3 ] at room temperature.
In this complex, the Mn
II and Fe
III ions are alternately arrayed by the bridging
ligand, mto, which forms the honeycomb network structure of [Mn
II Fe
III (mto) 3 ].
The (C 6 H 5 ) 4 P
+ layer is intercalated between two adjacent [Mn
II Fe
III (mto) 3 ] layers.
In the case of (n-C 4 H 9 ) 4 N[Zn
II Fe
III (ox) 3 ] with a similar structure of
(C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ], the χ T value (= 4.22 cm
3 K mol
−1 ) is almost constant
between 300 and 4.2 K, whose value is regarded as the spin-only χ T value (4.375 cm
3
K mol
−1 ) of the HS state (S = 5/2) for Fe
III [21]. On the other hand, the χ T value
for (C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ] decreases from 3.60 (at 300 K) to 2.66 cm
3 K mol
−1
(at 4.2 K) [3]. Therefore, the χ T value of (C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ] is considered
to be situated in the middle value between those of the HS and LS states for Fe
III .
Figure 6.7a shows the X-band ESR spectra for (C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ] at 300,
77 and 10 K, in which the ESR signals corresponding to the HS and LS states
N. Kojima and A. Okazawa
Fig. 6.6 Spin states of the Fe III sites for [Fe III (ox) 3 ], [Fe III (dto) 3 ], and [Fe III (mto) 3 ]
tris(monothiocarbamato)iron(III) complexes, on the other hand, the rapid spin equilibrium occurs in which the HS and LS states exchange in the time scale of less
than 10
−7 s [19]. In this case, an averaged quadrupole doublet between the HS and
LS states is observed. However, the rapid spin equilibrium phenomenon has not yet
been found for assembled metal complex systems. For this viewpoint, in order to
search the rapid spin equilibrium phenomenon for assembled metal complex system
including Fe
III O 3 S 3 site, we have synthesized (C 6 H 5 ) 4 P[M
II Fe
III (mto) 3 ] (M = Mn,
Zn) consisting of the Fe
III O 3 S 3 and M
II O 6 sites and investigated the spin state of the
Fe
III O 3 S 3 site [3].
Based on the crystal structure of (n-C 3 H 7 ) 4 N[Fe
II Fe
III (dto) 3 ] analyzed by the
single-crystal X-ray diffraction [20], the Rietveld analysis was performed for the
powder X-ray diffraction pattern of (C 6 H 5 ) 4 P[Mn
II Fe
III (mto) 3 ] at room temperature.
In this complex, the Mn
II and Fe
III ions are alternately arrayed by the bridging
ligand, mto, which forms the honeycomb network structure of [Mn
II Fe
III (mto) 3 ].
The (C 6 H 5 ) 4 P
+ layer is intercalated between two adjacent [Mn
II Fe
III (mto) 3 ] layers.
In the case of (n-C 4 H 9 ) 4 N[Zn
II Fe
III (ox) 3 ] with a similar structure of
(C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ], the χ T value (= 4.22 cm
3 K mol
−1 ) is almost constant
between 300 and 4.2 K, whose value is regarded as the spin-only χ T value (4.375 cm
3
K mol
−1 ) of the HS state (S = 5/2) for Fe
III [21]. On the other hand, the χ T value
for (C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ] decreases from 3.60 (at 300 K) to 2.66 cm
3 K mol
−1
(at 4.2 K) [3]. Therefore, the χ T value of (C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ] is considered
to be situated in the middle value between those of the HS and LS states for Fe
III .
Figure 6.7a shows the X-band ESR spectra for (C 6 H 5 ) 4 P[Zn
II Fe
III (mto) 3 ] at 300,
77 and 10 K, in which the ESR signals corresponding to the HS and LS states