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composition involving hydroxide ligands. The structure of bismuth dis-
alicylate hydrate is currently the only known crystal structure for a bismuth
salicylate complex without auxiliary organic ligands.
92
7.6.3 Luminescent Materials
One of the first investigations of the potential of mechanochemistry for the
synthesis of luminescent metal-organic materials has been reported by
Braga et al. who exploited neat grinding, as well as kneading, for the syn-
thesis of coordination polymers involving luminophoric copper(
I
) iodide
clusters.
93
The poorly soluble copper(
I
) iodide was readily transformed into a
set of isostructural 2D coordination polymers by mechanochemical milling
or kneading with either piperazine or dabco (Figure 7.11a). The luminescent
properties of the prepared materials polymers arise from the presence of
Cu
2
I
2
dimeric units that are separated by organic ligands so as to form 2D
frameworks.
94
The mechanochemical syntheses provided a clear benefit over
conventional solution syntheses by allowing the direct use of copper(
I
)io-
dide precursor whose application in conventional solution-based synthesis is
often complicated due to poor solubility. This work was subsequently ex-
tended towards the synthesis of discrete luminescent complexes by grinding
of copper(
I
) iodide with the bidentate ligand diphenyl(2-pyridyl)phosphine
(dpn) by LAG.
95
Ball milling of these two components in a 2 : 3 stoichiometric
ratio and in the presence of a small amount of acetonitrile provided
the discrete dimeric complex Cu
2
I
2
(dpn)
3
, which exhibits a maximum of
fluorescent emission at 525 nm, associated with a butterfly-shaped Cu
2
I
2
unit. In contrast, milling in the presence of chloroform as the grinding
Figure 7.11 Mechanochemical synthesis of luminescent coordination polymers
containing the Cu
2
I
2
unit by milling of solid copper(
I
) iodide with
piperazine or dabco;
93
(b) synthesis of the OLED material Alq
3
by a
combination of mechanochemistry and thermal desolvation.
11
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