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 (<b>1</b>) 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 (<b>1</b>)·(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 (<b>1</b>)₂·(Et₃BuN⁺Br^–) crystallizes in the cubic <i>Ia</i>3̅ space group (<i>a</i> = 22.573(5) Å, <i>V</i> = 11502(4) ų), with the Br^– ion located on 3̅ site and molecule <b>1</b> on a 3-fold axis. The 6-fold, unprecedented octahedral coordination of the bromide anion generates an hexagonal three-dimensional network of <i>Pa</i>3̅ 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>I</i> centering gives rise to a 2-fold interpenetration of class <i>Ia</i>, while the cations and solvent molecules are found disordered within interconnected cavities. Another related cubic structure of comparable unit cell volume (space group <i>Pa</i>3̅, <i>a</i> = 22.4310(15) Å, <i>V</i> = 11286.2(13) ų) is found with (<b>1</b>)₂·(Et₃S⁺I^–)