Do perfluoroarene⋯arene and C–H⋯F interactions make a difference to the structures of 4,2′:6′,4′′-terpyridine-based coordination polymers?

Abstract

The consequences for the structures of coordination polymers of introducing fluoro substituents into the terminal phenyl domain of 4′-(biphenyl-4-yl)-4,2′:6′,4′′-terpyridine (1) have been investigated. Reaction between Cu(OAc)₂·H₂O and 4′-(2′,3′,4′,5′,6′-pentafluorobiphenyl-4-yl)-4,2′:6′,4′′-terpyridine (2) yields the one-dimensional coordination polymer [Cu₂(μ-OAc)₄(2)]_n which contains paddle-wheel {Cu₂(OAc)₄} nodes bridged by ligands 2. The compound is isostructural with [Cu₂(μ-OAc)₄(1)]_n. When Cu(OAc)₂·H₂O reacts with a 1 : 1 mixture of 1 and 2, [Cu₂(μ-OAc)₄(1)]_n and [Cu₂(μ-OAc)₄(2)]_n co-crystallize with 1 and 2 disordered over one ligand site; the one-dimensional coordination polymer is isostructural with each of [Cu₂(μ-OAc)₄(1)]_n and [Cu₂(μ-OAc)₄(2)]_n indicating that replacing H by F substituents in the peripheral arene ring has no effect on the overall solid-state structure: tpy⋯tpy π-stacking is preserved, arene⋯arene π_H⋯π_H interactions are replaced by perfluoroarene⋯arene π_F⋯π_H interactions, and H⋯H contacts are replaced by H⋯F interactions. In stark contrast to the latter observations, the reaction of Zn(OAc)₂·2H₂O with perfluoro derivative 2 yields [Zn₅(OAc)₁₀(2)₄·11H₂O]_n as the dominant one-dimensional polymer; minor amounts of the anticipated polymer [Zn₂(μ-OAc)₄(2)]_n are also formed. The solid-state structure of [Zn₅(OAc)₁₀(2)₄·11H₂O]_n consists of quadruple-stranded polymer chains assembled from {Zn₅(2)₄} subchains interconnected by {Zn₅(OAc)₁₀} units. Within each chain, π_F⋯π_F and π_H⋯π_H stacking interactions are dominant, while the observed assembly of chains into sheets and π-stacking between arene units in adjacent sheets mimic the dominant interactions in the single-stranded chains observed in [Zn₂(μ-OAc)₄(1)]_n, [Zn₂(μ-OAc)₄(2)]_n, [Cu₂(μ-OAc)₄(1)]_n, [Cu₂(μ-OAc)₄(2)]_n and [Cu₂(μ-OAc)₄(1)]_n·[Cu₂(μ-OAc)₄(2)]_n.