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 πH⋯πH interactions are replaced by perfluoroarene⋯arene πF⋯πH 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, πF⋯πF and πH⋯πH 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.
Highlights
We have recently reported the assembly of coordination polymers containing the functionalized 4,2′:6′,4′′-terpyridine 1 (Scheme 2) and have discussed the role that face-to-face πstacking of pairs of biphenyl domains and pairs of tpy Scheme 2 Ligand structures and numbering for NMR spectroscopic assignments
We must make a clear distinction between assembling a MOF using organic linkers carrying terminal carboxylate groups which act as the donors in {M2(μ-O2CR)4} or other metal carboxylate-based building blocks[47] and using metal acetate salts combined with organic linkers bearing donor atoms which bind in axial sites of {M2(μ-O2CR)4} domains to generate coordination polymers
Coordination polymers formed from the pentafluoro derivative 2 and copper(II) or zinc(II) acetates have been prepared and structurally characterized, and their structures were compared with those produced with the all hydrogen analogue 1
Summary
Paper mol−1.11) More subtle factors may tip the balance. For example, the compounds shown in Scheme 1a crystallize with no face-to-face πH⋯πF interactions.[16]. The reaction mixture was stirred at room temperature for 20 h, during which time a white precipitate formed This solid was collected by filtration, washed well with H2O and EtOH, and dried in vacuo over P2O5. The test tube was sealed with parafilm and allowed to stand for 1 week at room temperature, after which time turquoise-green crystals had formed. A solution of Zn(OAc)2·2H2O (21.8 mg, 0.1 mmol) in MeOH (5.0 mL) was added carefully, and the tube was sealed with parafilm. After 10 days at room temperature, colourless crystals had formed These proved to be a mixture of colourless blocks of [Zn2(OAc)4(2)]n and colourless plates of [Zn5(OAc)10(2)4·11H2O]n. A solution of Cd(OAc)2·2H2O (26.7 mg, 0.100 mmol) in MeOH (5.0 mL) was added carefully, and the tube was sealed with parafilm and left for 3 weeks at room [Cu2(OAc)4(2)]n.
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