2-Aminopyridinium
(2-amino-5-bromopyridine)tribromocuprate(II) 1 and
bis(2-aminopyridinium) tetrabromocuprate(II) 2 have
been prepared from acetonitrile solutions containing CuBr
2
,
HBr and 2-aminopyridine in 1∶2∶2 and 1∶2∶1 molar
ratio, respectively. The mother-liquor of 1 was photoirradiated
with a superhigh-pressure mercury lamp and the organic base underwent
partial electrophilic para bromination of the substituted
pyridine ring. The compounds have been characterised by elemental
analysis, IR, UV/VIS and ESR spectroscopies, thermal analysis,
variable-temperature magnetic susceptibility measurements and
single-crystal X-ray diffraction. The crystal structure of 1
consists of infinite zigzag chains of
[C
5
H
7
N
2
]
+
cations and
distorted
[CuBr
3
(C
5
H
5
BrN
2
)]
-
tetrahedral anions running along the b axis and
held together by means of
N–H · · · Br hydrogen
contacts and non-covalent interactions between the π systems of the
pyridine rings. In 2 organic cations and flattened
[CuBr
4
]
2-
anions form two-dimensional
N–H · · · Br
hydrogen-bonded sheets which are connected by electrostatic
interactions, van der Waals forces and face-to-face stacking
interactions between the π systems of the aromatic cations. Magnetic
susceptibility measurements of powdered samples showed that both
compounds exhibit weak antiferromagnetic exchange interactions
[J = -1.20 (1), -2.43
cm
-1
(2)]. Thermal decomposition of both
compounds yielded copper(II) oxide and metallic Cu as stable
final residues in synthetic air and dinitrogen atmospheres,
respectively.
