# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2004
Supplementary Information
Magnetic Behavior of
Tetrakis[4-(N-tert-butyl-N-oxylamino)pyridine]bis(isocyanato
-N)cobalt(II) in Frozen Solution
Shinji Kanegawa,a Satoru Karasawa, a Motohiro Nakano,b and Noboru Koga*
Table of Contents

Figure S1. UV-Vis Spectra change for [Co(OCN)2(4NOPy)4] in MTHF solution in
the temperature range of 295–160 K
2.
Figure S2. T vs. T plots of [Co(OCN)2(4NOPy)4] in microcrystalline state and
frozen solution
3.
Figure S3. ’ vs. ” plot (Cole-Cole diagram) for [Co(OCN)2(4NOPy)4] in the
frozen MTHF solution.
4.
Figure S4. Mmol/NB vs. H/T plot of [Co(OCN)2(4NOPy)4] in a frozen MTHF
solution
5.
Figure S5. a) ’T - vs. T and b) ” vs. T plots for [Co(SCN)2(4NOPy)4] in a frozen
MTHF solution
# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2004
Figure S1. UV-Vis Spectra change for [Co(OCN)2(4NOPy)4] in MTHF solution in the
temperature range of 295 – 160 K. The dot line in the inset shows the spectrum for the
solid sample and the perpendicular axis is arbitrary unit.
The spectra at 300 K for [Co(OCN)2(4NOPy)4] showed the two sets of absorptions in
visible and near-infrared regions (at 546, 584, 632, and 660 nm and at 968, 1292, and
1508 nm, respectively) due to the d-d transitions of C2v cobalt(II) complex having a
tetrahedral structure. On cooling, new absorption at 470 nm gradually increased at the
expense of absorptions due to tetrahedral structure. The absorptions in both regions
completely disappeared and new ones at 470 and 1020 nm at 160 K. Especially, the
latter absorption is characteristic to the octahedral structure due to the d-d transition .
No shift of absorption was observed below 160 K (to 20 K). Temperature dependent
UV-Vis spectra suggest that the equilibrium between the tetrahedral and octahedral
structures for Co(II) complexes in solution leans to the former at room temperature and
shifted to the latter on cooling. In measurements of UV-Vis spectra of the solid-state
sample ( or in KBr pellet), the weak absorption at ~1020 nm observed in the solution
sample at 160 K was detected at ~1060 nm as a peak (see the inset of Figure S1).
# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2004
Figure S2. T vs. T plots of [Co(OCN)2(4NOPy)4] in microcrystalline state (filled
circle) and frozen solution (open circle)
# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2004
Figure S3. The plot of ’ vs. ” (Cole-Cole diagram) at 4.2 K for
[Co(OCN)2(4NOPy)4] in the frozen MTHF solution. The solid lines are least-square
fittings of the complex susceptibilities to the Cole-Cole’s semicircle law (equation 1).
The parameters (equation 2) obtained from the fitting of data in the  ‘ vs. T plot are
listed in below.
* = ∞ + (0 – ∞)/[1 + (i0)(1-)]
'() = • +
equation 1
( - • )[ 1 + ( )1-sin1/2
1 + 2()1 -sin1/2 + ( )2(1- )
equation 2
T(K)
∞(emumol-1)
0 (emumol-1)
 (s)

4.0
0.385
2.09
0.0805
0.20
4.2
0.384
1.97
0.0445
0.16
4.5
0.380
1.83
0.0180
0.14
5.0
0.382
1.65
0.0054
0.09
# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2004
Figure S4. a) Mmol/NB vs. H/T and b) ) T vs. T plots of Co(OCN)2(4NOPy)4 in a
frozen MTHF solution. The solid lines are the theoretical curves based on the ligand
field theoretical model. c) E vs. Ms diagram obtained by the optimized parameters.
# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2004
c)
150
2
2
3
3
E / kB K
100
3
3
1
50
1
1
1
1
1
0
-2.5
-1.5
-0.5
0.5
1.5
2.5
MS
Effective Hamiltonian:
4
4
 3

1 ˆ2 3 ˆ ˆ
2
ˆ
ˆ
ˆ
ˆ
ˆ
ˆ
H    (Lz  L )  kL  S0  2J  S0  Si  B kL  ge  Si  B
3
2
 2

i1
i 0

Optimized parameters:
Stevens’ orbital reduction factor: k = 1.0 (fixed)
Low-symmetry ligand field:  / kB = -960 K
g-factor for electron spin: ge = 2.0023 (fixed)
Spin-orbit coupling:  / kB = -250 K
Superexchange interaction: J / kB = 29.0 K
Theoretical study on the magnetic property of the complex will be discussed in detail
elsewhere.
# Supplementary Material (ESI) for Chemical Communications
# This journal is © The Royal Society of Chemistry 2004
Figure S5. a) ’T - vs. T and b) ” vs. T plots for Co(SCN)2(4NOPy)4 in a frozen
MTHF solution The solid lines are visual guides. The inset shows Arrhenius plot.
a)
b)