| Summary: | We report the preparation and characterization of 4′-([1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (<b>1</b>), 4′-(4′-fluoro-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (<b>2</b>), 4′-(4′-chloro-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (<b>3</b>), 4′-(4′-bromo-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (<b>4</b>), and 4′-(4′-methyl-[1,1′-biphenyl]-4-yl)-3,2′:6′,3″-terpyridine (<b>5</b>), and their reactions with copper(II) acetate. Single-crystal structures of the [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>L]<i><sub>n</sub></i> 1D-coordination polymers with L = <b>1</b>–<b>5</b> have been determined, and powder X-ray diffraction confirms that the single crystal structures are representative of the bulk samples. [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>(<b>1</b>)]<i><sub>n</sub></i> and [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>(<b>2</b>)]<i><sub>n</sub></i> are isostructural, and zigzag polymer chains are present which engage in π-stacking interactions between [1,1′-biphenyl]pyridine units. 1D-chains nest into one another to give 2D-sheets; replacing the peripheral H in <b>1</b> by an F substituent in <b>2</b> has no effect on the solid-state structure, indicating that bifurcated contacts (H...H for <b>1</b> or H...F for <b>2</b>) are only secondary packing interactions. Upon going from [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>(<b>1</b>)]<i><sub>n</sub></i> and [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>(<b>2</b>)]<i><sub>n</sub></i> to [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>(<b>3</b>)]<i><sub>n</sub></i>, [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>(<b>4</b>)]<i><sub>n</sub></i>, and [Cu<sub>2</sub>(μ-OAc)<sub>4</sub>(<b>5</b>)]<i><sub>n</sub></i>·<i>n</i>MeOH, the increased steric demands of the Cl, Br, or Me substituent induces a switch in the conformation of the 3,2′:6′,3″-tpy metal-binding domain, and a concomitant change in dominant packing interactions to py–py and py–biphenyl face-to-face π-stacking. The study underlines how the 3,2′:6′,3″-tpy domain can adapt to different steric demands of substituents through its conformational flexibility.
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