electronic states that depend on the distance between the com-
plex molecules. Such crystalline materials could find applications
in mechanical sensing.
V. Conclusions and Open QuestionsIn conclusion, the number of functional aggregates in which
new properties are generated by the assembly process is already
very large and growing every day. We have shown that it is pos-
sible or potentially achievable to modulate optical properties,
catalytic activity, conductivity, magnetic and mechanical pro-
perties and to have sensing behavior. The role played by the lig-
ands coordinated to the metal ions and the solvents in which the
assemblies are formed are key parameters for the interactions
within aggregates. In fact, a clever design of the organometallic
species can lead to aggregates with emerging properties and
novel functions that can be reversibly and dynamically tuned.
This behavior resembles the dynamic nature of living systems
able to self-organize and adapt in different environments. The
question is how much we can rationalize the behavior and pre-
dict the soft structures on the basis of the molecular design.
Can we foresee that also with metal complexes we are able to
interconvert from a soft structure, for example, micelle to
another one, for example, fibers or gels by an external input?
How far could we go in studying the interactions of such respon-
sive (nano)structures with others, for example, recognition of bio-
molecules, creation of artificial patterned surfaces, multicatalytic
sites using different activatable catalysts? How many different
metal complexes acting as energy and electron donor or acceptor
species could we organize, for instance, to realize an artificial
noncovalent light-harvesting system? Could we have crystalline
materials in which we could use the metal complex framework
to perform photoinduced multiredox reactions inside the
cavities?
Many more questions will arise from the development of this
fascinating area combining functional chemical structures and
intermolecular interactions. Further, looking at interface pro-
blems will be made possible with suitable model systems, and
the construction of organic and inorganic hybrid assemblies. We
are aware that many scientists all over the world are working
on such problems and have answered to some of our questions.
And for those who are entering the field, we believe that there
are so many exciting systems to create and to study that we will
have to write several more book chapters.
PHOTOPHYSICS OF MOLECULAR ASSEMBLIES 93