Switching the Conformation of 3,2′:6′,3″-tpy Domains in 4′-(4-n-Alkyloxyphenyl)-3,2′:6′,3″-Terpyridines

The preparation and characterization of 4′-(4-n-octyloxyphenyl)-3,2′:6′,3″-terpyridine (8) and 4′-(4-n-nonyloxyphenyl)-3,2′:6′,3″-terpyridine (9) are reported. The single crystal structures of 4′-(4-n-hexyloxyphenyl)-3,2′:6′,3″-terpyridine (6), 4′-(4-n-heptyloxyphenyl)-3,2′:6′,3″-terpyridine (7), and compounds 8 and 9 have been determined. The conformation of the 3,2′:6′,3″-tpy unit is trans,trans in 6 and 7, but switches to cis,trans in 8 and 9. This is associated with significant changes in the packing interactions with a more dominant role for van der Waals interactions between adjacent n-alkyloxy chains and C–H(methylene)... π interactions in 8 and 9. The solid-state structures of 6 and 7 with the n-hexyloxy and n-heptyloxy chains feature interwoven sheets of supramolecular assemblies of molecules, with pairs of n-alkyloxy chains threaded through cavities in an adjacent sheet.