Expanded Halogen-Bonded Anion Organic Networks with Star-Shaped Iodoethynyl-Substituted Molecules: From Corrugated 2D Hexagonal Lattices to Pyrite-Type 2‑Fold Interpenetrated Cubic Lattices

Halogen
bonding interactions between halide anions and neutral polyiodinated
linkers are used for the elaboration of anion organic frameworks,
by analogy with well-known MOF derivatives. The extended, 3-fold symmetry,
1,3,5-tris­(iodoethynyl)-2,4,6-trifluorobenzene (1) cocrystallizes
with a variety of halide salts, namely, Et3S+I–, Et3MeN+I–, Et4N+Br–, Et3BuN+Br–, Me-DABCO+I–, Bu3S+I–, Bu4N+Br–, Ph3S+Br–, Ph4P+Br–,
and PPN+Br–. Salts with 1:1 stoichiometry
formulated as (1)·(C+,X–) show recurrent formation of corrugated (6,3) networks, with the
large cavities thus generated, filled either by the cations and solvent
(CHCl3) molecules and/or by interpenetration (up to 4-fold
interpenetration). The 2:1 salt formulated as (1)2·(Et3BuN+Br–)
crystallizes in the cubic Ia3̅ space group
(a = 22.573(5) Å, V = 11502(4)
Å3), with the Br– ion located on
3̅ site and molecule 1 on a 3-fold axis. The 6-fold,
unprecedented octahedral coordination of the bromide anion generates
an hexagonal three-dimensional network of Pa3̅
symmetry, as observed in the pyrite model structure, at variance with
the usual, but lower-symmetry, rutile-type topology. In this complex
system, the I centering gives rise to a 2-fold interpenetration
of class Ia, while the cations and solvent molecules
are found disordered within interconnected cavities. Another related
cubic structure of comparable unit cell volume (space group Pa3̅, a = 22.4310(15) Å, V = 11286.2(13) Å3) is found with (1)2·(Et3S+I–).