Fluorine–Fluorine Interactions in the Solid State: An Experimental and Theoretical Study

Abstract

The solid state structures of three compounds that contain a perfluorinated chain, CF(3)(CF(2))(5)CH(2)CH(CH(3))CO(2)H, CF(3)(CF(2))(5)(CH(2))(4)(CF(2))(5)CF(3) and {CF(3)(CF(2))(5)CH(2)CH(2)}(3)P═O have been compared and a number of C-F···F-C and C-F···H-C interactions that are closer than the sum of the van der Waals radii have been identified. These interactions have been probed by a comprehensive computational chemistry investigation and the stabilizing energy between dimeric fragments was found to be 0.26-29.64 kcal/mol, depending on the type of interaction. An Atoms-in-Molecules (AIM) study has confirmed that specific C-F···F-C interactions are indeed present, and are not due simply to crystal packing. The weakly stabilizing nature of these interactions has been utilized in the physisorption of a selected number of compounds containing long chain perfluorinated ponytails onto a perfluorinated self-assembled monolayer, which has been characterized by IRRAS (Infrared Reflection Absorption Spectroscopy).

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].…”

Understanding of Noncovalent Interactions Involving Organic Fluorine

“…2.21 and 2.22) [117]. Selected dimers consisting of these interactions were extracted from the crystal packing and the interaction energy were calculated at DFT/B97-D using aug-cc-pVnZ, where n = D, T, or Q. basis set and stabilization energy ranging from 0.26 to 29.64 kcal/mol were Recently, shortest F···F distances were reported (2.596(3) Å, type I, Fig.…”

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

“…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.…”