The intramolecular blue-shifting C-H•••F-C hydrogen bond: crystal structure of [4,4′-bis(HCF2CF2CF2CF2CH2OCH2)-2,2′-bpy]MCl2 where M = Pt, Pd

In the solid state, the two fluorous ponytails in [4,4'-bis(HCF2CF2CF2CF2CH2OCH2)-2,2'-bpy]MCl2 (M = Pt 2; Pd 3) reveal one with a transoidal HCF2CF2CF2CF2CH2- chain on carbon backbone, similar to that with a normal fluorous alkyl group, and the other with a cisoidal HCF2CF2 CF2CF2CH2-chain on a carbon backbone, exhibiting an intramolecular blue-shifting C-H/center dot center dot center dot F-C hydrogen-bond. With the contraction of C-H bond, the increase in C-H stretch and the short H center dot center dot center dot F distance, these two examples are among the blue-shifting hydrogen bonds as defined by Hobza et al. The calculated C-H stretches using periodic density functional theory (DFT) are in good agreement with IR observations.