Controlling the switching
efficiency of photoactive hybrid systems
is an obligatory key prerequisite for systematically improving the
design of functional materials. By modulating the degree of fluorination
and the amount being embedded into porous hosts, the
E
/
Z
ratios of fluorinated azobenzenes were adjusted
as both functions of substitution and the degree of loading. Octafluoroazobenzene
(F8-AZB) and perfluoroazobenzene (F10-AZB) were inserted
into porous DMOF-1. Especially for perfluoroazobenzene (F10-AZB),
an immense stabilization of the
E
isomer was observed.
In complementary molecular dynamics simulations performed at the DFTB
(density functional tight binding) level, an in-depth characterization
of the interactions of the different photoisomers and the host structure
was carried out. On the basis of the resulting structural and energetic
data, the experimentally observed increase in the amount of the
Z
conformer for F8-AZB can be explained, while the stabilization
of
E
-F10-AZB can be directly related to a fundamentally
different interaction motif compared to its tetra- and octafluorinated
counterparts.