Synthesis, X-ray Characterization and Density Functional Theory (DFT) Studies of Two Polymorphs of the α,α,α,α, Isomer of Tetra--Iodophenyl Tetramethyl Calix[4]pyrrole: On the Importance of Halogen Bonds.

This manuscript reports the improved synthesis of the α,α,α,α isomer of tetra--iodophenyl tetra-methyl calix[4]pyrrole and the X-ray characterization of two solvate polymorphs. In the solid state, the calix[4]pyrrole receptor adopts the cone conformation, including one acetonitrile molecule in its aromatic cavity by establishing four convergent hydrogen bonds between its nitrogen atom and the four pyrrole NHs of the former. The inclusion complexes pack into rods, displaying a unidirectional orientation.