complexes must be different. This is the reason for choosing the
luminescent ionic complexes possessing complementary colors
and high-emission quantum yields.
We were able to precipitate the double salts ( 1 ) as crystalline
materials suitable for single-crystal X-ray analysis, and the
structure of one of them shows that they form fascinating 3D
porous networks (Fig. 9). As can be easily seen, the pores are
formed because of several noncovalent interactions which held
together the entire crystalline structure. We noticed that to be
able to crystallize the material, a number of characteristics must
be incorporated into the building blocks. First, the complexes
must have equal and opposite net charges (1), the same geom-
etry (in this case, octahedral,C 2 symmetry) to simplify crystal
packing, and they must possess as substituents of the coordinated
ligands groups able to induce weak interactions as, for exam-
ple, fluorine to promote halogen–hydrogen or halogen–halogen
interactions.
The resulting 3D crystalline supramolecular network devotes
about 20% of its volume to host CH 2 Cl 2 molecules. The large
and isolated channels run along the crystallographiccaxis and
display an irregular shape with a minimum cross-section of
3.511.5 Å^2 , which is able to accommodate a sphere whose
diameter is 5.1 Å. Interestingly, upon removal of the solvent from
the channels, the crystallinity of the compound decreases, but
the porosity is maintained. The process of filling and emptying
the pores is perfectly reversible, and we demonstrated that the
porous network possesses cavities able to host solvent molecules,
or electroactive molecules. In the absence of a guest, we observed
not only that the emission of the blue-green emitter is completely
quenched by energy transfer but also that the emission of the
single crystal is bathochromically shifted with respect to the ones
which are supposed to be the smaller band gap species, namely,
the cations. As revealed by a closer analysis of the packing of sin-
gle crystal of 1 , a strong p–pinteraction (d¼3.4 Å) is present
between the complementary iridium components. Most likely,
this interaction leads to a kind of exciplex formation and emis-
sion from a corresponding lower-energy excited state.
Insertion of toluene molecules inside the pores, which most
likely increases the distance between the complexes due to the
breathing of the crystal, was monitored by confocal microscopy,
and a blue shift of the emission accompanied by the visualization
of the energy transfer process was detected.
Even more interesting was the possibility to almost selectively
quench the cationic iridium complexes by efficient photoinduced
electron transfer and to modulate the color of emission of the
PHOTOPHYSICS OF MOLECULAR ASSEMBLIES 69