Cocrystallization may alter material
physicochemical properties;
thus, the strategy of forming a cocrystal is generally used to improve
the material performance for practical applications. In this study,
two transition-metal complex cocrystals [Zn(bpy)
3
]H
0.5
BDC·H
1.5
BDC·0.5bpy·3H
2
O (
1
) and [Cu
2
(BDC)(bpy)
4
]BDC·bpy·2H
2
O (
2
) have been achieved using a hydrothermal
reaction, where bpy and H
2
BDC represent 2,2′-bipyridine
and benzene-1,3-dicarboxylic acid, respectively. Cocrystals were characterized
by microanalysis, infrared spectroscopy, and UV–visible spectroscopy.
Cocrystal
1
contains five components and crystallizes
in a monoclinic space group
P
2
1
/
n
. The H
0.5
BDC
1.5–
, H
1.5
BDC
0.5–
, and H
2
O molecules construct
three-dimensional H-bonding organic framework; the [Zn(bpy)
3
]
2+
coordination cations and
uncoordinated bpy molecules reside in channels, where two coordinated
bpy ligands in [Zn(bpy)
3
]
2+
and one uncoordinated
bpy adopt sandwich-type alignment via π···π
stacking interactions. Cocrystal
2
with four components
crystallizes in a triclinic space group
P
-1 to form
alternating layers; the binuclear [Cu
2
(bpy)
4
(BDC)]
2+
cations and uncoordinated bpy molecules build
the cationic layers, and the BDC
2–
species with
disordered lattice water molecules form the anionic layers. Cocrystal
1
shows intense photoluminescence at an ambient condition
with a quantum yield of 14.96% and decay time of 0.48 ns, attributed
to the π* → π electron transition within phenyl/pyridyl
rings, and
2
exhibits magnetic behavior of an almost
isolated spin system with rather weak antiferromagnetic coupling in
the [Cu
2
(bpy)
4
(BDC)]
2+
cation.
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