Study of a new fluorinated compound: variable-temperature crystallography, thermal expansion, theoretical...

Butane-1,4-diyl bis(trifluoromethane-1-sulfonate), C₆H₈F₆O₆S₂ or Bu(OTf)₂, crystallizes in the monoclinic space group P2₁/c, with the crystal packing mainly stabilized by chalcogen and fluorine-fluorine interactions. Temperature-dependent X-ray diffraction measurements reveal smooth, continuous and anisotropic thermal expansion without any indication of phase instability or structural phase transition. The anisotropic contraction along the a and b axes leads to progressive shortening of the intermolecular distances and a concomitant reorganization of the short intermolecular contacts, consistent with SAPT2/jun-cc-pVDZ interaction energies calculated for dimers extracted from the crystal structures. Notably, theoretical conformational searches failed to reproduce the solid-state geometry. Biological assays indicate that Bu(OTf)₂ does not exhibit cytotoxic properties toward either leukemia cells or healthy cells. Gravimetric measurements further indicate that Bu(OTf)₂ is poorly soluble in water.