Halogen Bonding in Dithiane/Iodofluorobenzene Mixtures: A New Class of Hydrophobic Deep Eutectic Solvents

Abstract

While research into deep eutectic solvents (DESs) has expanded over the previous two decades, the focus has remained on the utilization of hydrogen bond donors in these systems. Additionally, the majority of the known DESs rely on at least one ionic component. Through the combination of 1,3‐dithiane and 1,2‐diiodo‐3,4,5,6‐tetrafluorobenzene (1,2‐F4DIB), we report the first known DES based on halogen bonding. This mixture remains a liquid, with a eutectic melting temperature of 13.7 °C over a range of 1,3‐dithiane mole fraction (0.35 to 0.75). Additionally, cocrystals of 1,3‐ and 1,4‐dithiane with 1,2‐, 1,3‐, and 1,4‐F4DIB, as well as 1,3,5‐trifluoro‐2,4,6‐triiodobenzene were studied via single‐crystal X‐ray diffraction. These data reveal a wide range of halogen bonding strengths (0.85<RXB<0.99; RXB=normalized halogen bond distance parameter) and geometries about the sulfur atom. By including intermolecular interactions beyond hydrogen bonding, the scope of possible DES systems can be greatly expanded.

Everything You Wanted to Know about Deep Eutectic Solvents but Were Afraid to Be Told

“…The definition introduced above has several advantages. It restricts DESs to a subclass of eutectic mixtures, forcing these mixtures to at least have negative deviations from thermodynamic ideality due to favorable enthalpic interactions between the two precursors that result from the sharing of a proton through some sort of hydrogen bond or any other type of strong interaction [e.g., halogen bonds (15)]. This precludes the systems in which the acidity difference between the Lewis or Brønsted acids and bases is so strong that proton transfer does take place, or mixtures whose nonideality is driven by entropic factors [e.g., mixtures with polymers where the nonideality is dominated by the combinatorial part of the excess Gibbs free energy as described by a Flory-Huggins type of contribution (16)].…”

High-Performance Flexible Ionically Conductive Superhydrophobic Papers via Deep Eutectic Polymer-Enhanced Interfacial Interactions

“…As a new type of green solvent, deep eutectic solvents (DESs) have gained wide attention in recent years in the fields of metal processing, gas adsorption, catalysts, lithium-ion batteries, and synthesis of functional materials. − DESs consist of hydrogen bond donors and hydrogen bond acceptors, and hydrogen bonding between the components can lead to a significant reduction in the melting point of their mixtures, resulting in a clear, homogeneous liquid state at room temperature. − However, most of the reported types are hydrophilic, and their overall performance is susceptible to changes in moisture content or humidity. Hydrophobic DESs (HDESs) were first proposed in 2015 .…”

aquo-DESs: WATER-BASED BINARY NATURAL DEEP EUTECTIC SOLVENTS

“…The interactions occurring between the HBD and the HBA as well as between the same HBA-HBA and HBD-BHD lead to an impossible regular crystal lattice formation, therefore to liquid systems starting from high melting point components [13][14][15][16]. Also, other weak forces, such as halogen bonds or electrostatic interactions can occur in these liquids where the entropy and the inhomogeneity of the structures lead to liquids at the proper molar ratio, indicated as eutectic point [17][18][19]. The molecules that are reported in literature as capable for DESs formation are mainly carboxylic acids, polyols, alcohols, and so on as HBD, while ammonium or phosphonium salts, zwitterionic inner salts or neutral molecules such as acetamide as well as inorganic salts (also hydrates) are reported to be efficacious HBAs in the DESs formation [11,[20][21][22][23].…”