V. Concluding RemarksPhotoreactivity is a common feature of many components of
biological systems and their synthetic functional counterparts.
The important role of inorganic photochemistry and photo-
catalysis as a versatile tool for triggering, driving, and
controlling molecular processes by light will therefore certainly
be further increasing in the near future.
In this chapter, a unifying description of the most important
bioinorganic chromophores and their light-induced properties
has been provided. An attempt has been made to collect some
general guidelines for the rational design of biomimetic and
bioinspired systems based on photoreactive inorganic com-
pounds, which are key constituents of artificial photosynthetic
devices, functional enzyme mimetics, and light-sensitive
reagents for the controlled release of physiologically active spe-
cies. Processes based on this kind of photoresponsive molecules
inspired by nature are of crucial relevance for many cross-disci-
plinary research fields and provide a solid foundation for numer-
ous applications at the borderlines of chemistry, biology, and
medicine (5,6). At present, however, there are only a few
pioneering studies demonstrating the power of this novel
approach, which have already supplied a convincing proof of
principle for the fascinating new research fields ofbioinorganic
photochemistryandbiomimetic photocatalysisfounded about a
decade ago (3,8). We hope that our current review will be able
to stimulate further research efforts in this direction.
Besides novel frontiers in photosensitization and photocatalyis
in the context of bioinorganic systems, the photophysics and
photochemistry of inorganic materials also continues to be the
central discipline in the field of solar energy conversion and
renewable fuel production (87,220). One of the main future
challenges in this direction will be the search for much more
versatile types of photosensitizers with improved properties such
as intrinsic multielectron reactivity and light-absorption cha-
racteristics optimized for solar chemistry. Finally, in the long
run, the construction of more efficient systems for powering pho-
tocatalysis and artificial photosynthetic energy storage has to be
achieved with sustainable, environmentally benign and earth-
abundant building blocks (220,221). An example illustrating the
suggested way to follow ( 138 ) is given below (Fig. 25).
The widely applied class of photosensitizers derived from the
tris(2,2^0 -bipyridyl)ruthenium(II) cation [Ru(bpy) 3 ]^2 þ ( 101 ) is
based on one of the rarest metals on earth. Many high-valent
compounds of the platinum group metal ruthenium are further
280 GÜNTHER KNÖR AND UWE MONKOWIUS