Crystal and Solid-State Arrangement Trends of Halogenated Boron Subphthalocyanines

A series
of new crystal structures for the boron subphthalocyanine
(BsubPc) derivatives chloro hexachloro BsubPc (Cl-Cl6BsubPc),
chloro dodecachloro BsubPc (Cl-Cl12BsubPc), bromo/chloro
hexachloro BsubPc (Br0.27|Cl0.73-Cl6BsubPc), bromo dodecachloro BsubPc (Br-Cl12BsubPc), and
pentafluorophenoxy dodecachloro BsubPc (F5PhO-Cl12BsubPc) are reported. By combining these new crystal structures with
a series of previously published structures into a comprehensive study,
we have outlined several new structure crystal property/solid-state
arrangement relationships for this expanded list of BsubPc derivatives.
Parameters that were examined to establish the relationships include
(a) geometric descriptors of the BsubPc molecular structure including
the bowl shape of the BsubPcs; (b) molar density of the crystals;
and (c) void volume fraction (Φ). Variations in the peripheral
substituents (from hydrogen to fluorine and chlorine) were found to
have a profound effect on the solid-state arrangement. No significant
changes were noted when the axial substituent was varied from chlorine
to bromine, whereas replacement of the axial halide with a pentafluorophenoxy
fragment resulted in a notable change (as expected). It was also found
that Cl-C12BsubPc (and its derivatives) had a high tendency
to co-crystallize with solvents (form solvates), which resulted in
a significantly different solid-state arrangement. We believe the
observations detailed in this paper will lead to routes to engineer
the crystallization of BsubPcs to facilitate tailored solid-state
arrangement and properties.