The Evolution Aspect in the Crystallization Process of [5,5′‐(HCF₂CF₂CH₂OCH₂)₂‐2,2′‐bpy]MX₂ (M = Pt, Pd; X = I, Br): Role of the Intramolecular CF₂─H…X(─M) Hydrogen Bonds

The general species (2,2′‐bpy)MX 2 (M = Pd, Pt; X = Br, I) in a crystallization process results in an isomorphous convergence in P 2 1 /c. Yet, with polyfluorinated side chains, the general [5,5′‐(HCF 2 CF 2 CH 2 OCH 2 ) 2 ‐2,2′‐bpy]MX 2 species proceeds to crystallize the isomorphous structures of 5 (M = Pt; X = I) and 6 (M = Pd; X = I) in P 2 1 /c only; structure 7 (M = Pt; X = Br) crystallizes in P 2 1 /c but is not isomorphous with 5 and 6 , and structure 8 (M = Pd; X = Br) forms differently in P– 1. The causes making the system nonlinear are (1) the intramolecular CF 2 ─H … X(─M) hydrogen bonds found in 5–7 but not in 8, and (2) in response to the transition from I to Br, bifurcated [C─H … ] 2 F ─C hydrogen bonds that are formed in 5 and 6 and bifurcated C─ H [ … F─C] 2 hydrogen bonds in 7 . Additionally, the intramolecular CF 2 ─H … X(─M) hydrogen bonding from compounds 5–7 could be affirmed by the IR studies.