J. Breu et al., Crystal engineering as a tool for directed radiationless energy transfer in layered {Lambda-[Ru(bpy)(3)]Delta-[Os(bpy)(3)]}(PF6)(4), J AM CHEM S, 122(11), 2000, pp. 2548-2555
New types of crystal structures with new physical properties such as energy
harvesting can be engineered by exploiting the potentiality of chiral reco
gnition. In the proposed strategy one takes advantage of he possibility tha
t in true racemates one enantiomeric component in the crystal packing may b
e replaced by a different molecule of the same chirality and similar shape.
This opens the path to a number of new properties. In the present investig
ation, we demonstrate that a system can be engineered, in which homochiral
Layers of Lambda-[Ru(bpy)(3)](2+) rigorously alternate with homochiral laye
rs of Delta-[Os(bpy)(3)](2+). This arrangement is realized in {Lambda-[Ru(b
py)(3)]Delta-[Os(bpy)(3)]}(PF6)(4). Due to the deliberately introduced lowe
r dimensionality, the new crystalline system exhibits fascinating propertie
s, in particular with respect to an interplay of processes of interlayer an
d interlayer radiationless energy transfer. Interestingly, in this system i
t is possible to achieve a controlled accumulation of excitation energy on
a single crystallographic Delta-[Os(bpy)(3)](2+) site. Moreover, the excita
tion energy is absorbed in a wide range from the UV to the red side of the
visible by both Lambda-[Ru(bpy)(3)](2+) and Delta-[Os(bpy)(3)](2+) units, a
nd one observes an intense red/infrared and highly resolved emission only o
f the low-energy Delta-[Os(bpy)(3)](2+) site, irrespective of the excitatio
n wavelength used. The crystal structure of this newly engineered compound
is determined for both the room-temperature phase (P32, a 10.7012(5) Angstr
om, c 16.3490(10) Angstrom) as well as for the low-temperature phase (P3, a
= 18.4189(10) Angstrom, c = 16.2309(9) Angstrom).