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described below. Among the simplest halogenated nitronyl nitroxides
4a
-
c
(Scheme 2), only the bromo (
4b
)andiodo(
4c
) derivatives have been de-
scribed and structurally characterized [26]. These are isostructural and ex-
hibit short N - O
I (2.928(3)
A
)interactions.
Despite a similar molecular packing, the dominant magnetic interactions
in
4b
and
4c
are antiferromagnetic and ferromagnetic, respectively, with
Curie-Weiss temperatures above 150 Kof-2(
4b
)and+5 K(
4c
). The three
p
-halophenyl derivatives
5a
-
c
have also been structurally characterized [27-
29]. In the chloro compound
5a
(Fig. 1) [27], a type I Cl
Br (2.970(3)
A
)andN- O
···
···
···
Cl halogen inter-
action is identified rather than a Cl
···
O - N interaction, with the following
Cl 3.360(2)A,C- Cl
Cl 154.22(7)
◦
.
structural characteristics: Cl
···
···
Scheme 2
Halogenated nitronyl nitroxides
Fig. 1
Ty pe I C l
···
Cl interaction in the
p
-chlorophenyl nitronyl nitroxide
5a
The iodo derivative
5c
(Fig. 2) is characterized by a linear N - O
···
Iinter-
I distance (3.412(4)A)andN- O
action with a relatively long O
Iangle
(167.9(2)
◦
) [29]. The iodine atom lies on the plane defined by the nitronyl
···
···
Fig. 2
N - O
···
Iinteractioninthe
p
-iodophenyl nitronyl nitroxide
5c
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