Haloperfluorocarbons: Versatile Tectons in Halogen Bonding Based Crystal Engineering

摘要

The physical and chemical properties of perfluorocarbons (PFCs), and of their functional derivatives, are dramatically different from those of the corresponding hydrocarbons (HCs). For instance, aromatic PFCs and HCs have quadrupolar moments of similar magnitude, but of opposite sign (1). Aliphatic PFCs are endowed with greater compressibilities and viscosities but lower internal pressures and refractive indexes than HC parents. Due to the high ionization energy and low polarizability of fluorine atoms, saturated PFCs have particularly weak intermolecular interactions and low surface energies. Heats of solution and cohesive pressures of PFCs are remarkably different from those of corresponding HCs and enthalpies of interaction between PFCs and HCs are smaller than those between HCs. Thus, the miscibility of perfuorinated alkanes, ethers and tertiary amines with many organic solvents is quite limited (2-4). With more polar compounds such as water and organic or inorganic salts (OSs or ISs, respectively) the miscibility is even less.