POP-Type MMX-Chain Compounds with Binary Countercations and Vapochromism - Material Designs and New Physical Properties in MX-and MMX-Chain Compounds - page 217

Fig. 10.14 Temperature dependence of (a) spin susceptibility ( w ) and (b) ESR linewidth ( D H 1/2 )
obtained for the initial ( open circles ), dehydrated ( solid circles ), and rehydrated ( open triangles )
samples of K 2 (NC 3 N)[Pt 2 (pop) 4 I] 4H 2 O. The dashed curves in (a) represent the fitting by the
Curie law. The inset in (a) shows the plot of vs. T 1 obtained for the three dehydrated salts of

K 2 (NC 3 N)[Pt 2 (pop) 4 I] ( circles ), K 2 (Me-NC 3 N)[Pt 2 (pop) 4 I] ( rectangles ), and K 2 (Cl-NC 3 N)
[Pt 2 (pop) 4 I] ( triangles ). The solid lines show the fitting by the activation formula

D w Τ

The temperature dependence of the molar spin susceptibility ( w )ofK 2 (NC 3 N)

[Pt 2 (pop) 4 I] 4H 2 O and K 2 (NC 3 N)[Pt 2 (pop) 4 I] obtained by using ESR spectroscopy

(Fig. 10.14 ) indicates the interesting electronic state in the dehydrated state
[ 46 , 53 ]. Although the 4H 2 O followed the Curie law

(dashed line), which is consistent with the nonmagnetic ACP + CDW state, the

w of K 2 (NC 3 N)[Pt 2 (pop) 4 I]

of
K 2 (NC 3 N)[Pt 2 (pop) 4 I] gradually increased above about 80 K, and followed the
Curie law (dashed line) below about 80 K. The principal g values were determined
from the single-crystal rotation measurements at room temperature to reveal the
origin of the spin [ 53 ]. As a result, the anisotropic g value of uniaxial type with the
principal values of g // ¼

w

2.147 for the parallel and perpendicular
directions to the chain, respectively, were observed in the dehydrated state.
Observed anisotropy of g ⊥ >

1.966 and g ⊥ ¼

2 > g // is consistent with that expected for the low-

spin Pt 3+ ( S ¼ 1/2), where the unpaired electron resides on the Pt ð 5d z 2 Þ orbital.

The resultant susceptibility (

D w ¼ w

- w c ), where w c is Curie component, obeyed

an activation type equation above about 80 K: D wT ¼ C exp(- E g / k B T ), where C is

the Curie constant of activated spins, E g is the activation energy, and k B is the
Boltzmann constant. Concomitantly, the ESR linewidth ( D H 1/2 ) exhibited distinct

motional narrowing above the same temperature range as the spin excitation took
place, suggesting that the activated Pt 3+ spins are mobile solitons generated in the
doubly degenerated CDW state with small d (Pt-I-Pt). The origin of solitons are