The intramolecular blue-shifting C–H⋯F–C hydrogen bond: crystal structure of [4,4′-bis(HCF ₂ CF ₂ CF ₂ CF ₂ CH ₂ OCH ₂ )-2,2′-bpy]MCl ₂ 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 HCF2CF2CF2CF2CH2– chain on a carbon backbone, exhibiting an intramolecular blue-shifting C–H⋯F–C hydrogen-bond. With the contraction of C–H bond, the increase in C–H stretch and the short H⋯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.