3.3 Voronoi-Dirichlet polyhedra of the triplet excited
states
The Voronoi-Dirichlet polyhedra method allows one to reveal the features
of the coordination environment of the central ion and its effect on
intermolecular interactions. The VDP parameters can be used to identify
the valence state of the ion, crystal-chemical stability, phase
transitions of the first and second order, as well as the LC behavior of
Ln(III) coordination compounds. They were calculated for the Eu(III)
complexes in the optimized geometries of their ground and triplet
excited states.[69,70] The resulting VDP shapes
(Figure 5) are convex polyhedra with surfaces formed by planes passing
perpendicularly through the midpoints of the Eu–O and Eu–N bonds.