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: Supramolecular Interaction Directionality

The general species (2,2-bpy)MX2 (M=Pd, Pt; X=Br, I) in a crystallization process results in an isomorphous convergence in P2(1)/c. Yet, with polyfluorinated side chains, the general [5,5-(HCF2CF2CH2OCH2)(2)-2,2-bpy]MX2 species proceeds to crystallize the isomorphous structures of 5 (M=Pt; X=I) and 6 (M=Pd; X=I) in P2(1)/c only; structure 7 (M=Pt; X=Br) crystallizes in P2(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 (CF2HX)-X-...(M) hydrogen bonds found in 5-7 but not in 8, and (2) in response to the transition from I to Br, bifurcated [CH...](2)C hydrogen bonds that are formed in 5 and 6 and bifurcated C[(FC)-F-...](2) hydrogen bonds in 7. Additionally, the intramolecular (CF2HX)-X-...(M) hydrogen bonding from compounds 5-7 could be affirmed by the IR studies.