Further Evidence on the Importance of Fluorous–Fluorous Interactions in Supramolecular Chemistry: A Combined Structural and Computational Study

Abstract

The solid-state structures of CF3(CF2)5CH2CO2H and a fluorous triazole are reported, both of which display a wide variety and large number of noncovalent interactions in their packing. The solid-state structure of CF3(CF2)5CH2CO2H is stabilized by multiple F···F contacts but only one C–H···F–C interaction, as well as O–H···O and C–H···O hydrogen bonds. In contrast to other reported structures, the torsion angles in the fluorous chain are close to 180°, which means that the fluorine atoms are eclipsed. A DFT study of the interactions in both compounds show that F···F interactions, along with stacking and C–H···F and C–H···O contacts, are individually weakly energetically stabilizing, but collectively, they can give rise to interaction energies of up to 13 kcal mol–1. A topological approach to the interactions using atoms-in-molecules (AIM) theory reveals that there are bond critical points between the C–F···F–C interactions as well as C–F···H–C interactions that are not recognized when using only the van der Waals distances.

Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds

“…Th μ-O,O bidentate, bridging the donors to form remarkably similar 1-D polymeric Figure 2. Further analysis of the crystal packing revealed the donor-acceptor para be a result of F···F aggregation [38][39][40][41][42] between perfluorinated donor chains, wh than C−I···O − −N + XBs, play a crucial role to yield a robust 3-D crystal structure. with alternate acceptors and donors.…”

“…The N−O groups were μ-O,O bidentate, bridging the donors to form remarkably similar 1-D polymeric chains, as shown in Figure 2. Further analysis of the crystal packing revealed the donor-acceptor parallel arrangement to be a result of F···F aggregation [38][39][40][41][42] between perfluorinated donor chains, which, though weaker than C−I···O − −N + XBs, play a crucial role to yield a robust 3-D crystal structure. The strength of the C−H···O interaction is approximately one-third of conventional HBs [43][44][45][46][47][48][49] that operate between donors such as −N−H/−O−H and weak bases, and these interactions significantly increase the lattice energy of the co-crystals [50].…”

3-(1H,1H,2H,2H-Perfluorooctyl)-1-vinyl-4-imidazoline-2-thione

“…Related structures have been reported recently (Hummel et al, 2017), notably a 4-(1H,1H,2H,2H-perfluorooctyl)-1,2,4-triazolium salt (Adamer et al, 2011) and a data reports 1-(1H,1H,2H,2H-perfluorooctyl)-1,2,3-triazole (Omorodion et al, 2015) have been described.…”

“…The major component of the disordered fluoroalkyl chain adopts the typical helical conformation (Fournier et al, 2010;Jang et al, 2003) with an average CCCC twist angle (deviation from 180 ) of 11 . Specific C-FÁ Á ÁF-C interactions have been identified in fluorous molecules (Baker et al, 2012;Omorodion et al, 2015). Here, a short F9DÁ Á ÁF12C contact of 2.797 (6) Å is observed between the two chains (Fig.…”

Rapid self-healing and anion selectivity in metallosupramolecular gels assisted by fluorine–fluorine interactions

“…Beyond being a consequence of crystal packing, recent experimental and theoretical studies have supported the existence of F···F interactions and opened up new applications in supramolecular chemistry. 47,48 The fluorinated analogues of hydrocarbon compounds possess exceptional properties such as steric bulk, stiff and stable nature, simultaneous hydro-and lipophobicity, slower aggregation behaviour and lower critical gelation/aggregation concentration. These features of fluorinated counterparts offer a unique opportunity to design materials with unprecedented properties.…”