Molecular Packing and Singlet Fission: The Parent and Three Fluorinated 1,3-Diphenylisobenzofurans

Crystal
structures, singlet fission (SF) rate constants, and other
photophysical properties are reported for three fluorinated derivatives
of 1,3-diphenylisobenzofuran and compared with those of the two crystal
forms of the parent. The results place constraints on the notion that
the effects of molecular packing on SF rates could be studied separately
from effects of chromophore structural changes by examining groups
of chromophores related by weakly perturbing substitution if their
crystal structures are different. The results further provide experimental
evidence that dimer-based models of SF are not sufficiently general
and that trimer- and possibly even higher oligomer-based or many-body
models need to be formulated.