New approaches to sugar-functionalised 2,2′:6′,2″-terpyridines based upon tetrafluorophenoxy spacers; crystal and molecular structures of 4′-(tetrafluoro-4-hydroxyphenyl)-2,2′:6′,2″-terpyridine and 4′-(4-methoxytetrafluorophenyl)-2,2′:6′,2″-terpyridine

The new ligand 4`-pentafluorophenyl-2,2`:6`,2``-terpyridine (2) has been prepared with a view to utilising the electrophilic reactivity at the 4-position of the substituent to provide access to sugar-functionalised compounds. Although 2 reacts cleanly with simple alcohols, attempts to incorporate spacers or to attach sugars were unsuccessful. However, dealkylation of the 4`-(4-alkoxytetrafluorophenyl)-2,2`:6`,2``-terpyridines gave the corresponding phenol in good yield. Solid state structures of 4`(tetrafluoro-4-hydroxyphenyl)-2,2`:6`,2``-terpyridine (5) and 4`-(4-ethoxytetrafluorophenyl)-2,2`:6`,2``-terpyridine (4) are reported; the former compound has an extremely unusual cis, trans configuration of the pyridine rings as a result of intermolecular hydrogen bonding involving the phenol. Iron(II) complexes of 2 and 4 have been prepared; the compounds behave as typical tpy ligands and the fluorinated phenyl substituents are strongly electron-withdrawing. The reaction of the phenol 5 with electrophiles allows access to new 4`-(4-alkoxytetrafluorophenyl)-2,2`:6`,2``-terpyridines and by using 2-bromoethyl-2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside as electrophile, the, glucose-functionalised ligand 9 and the iron(II) complex [Fe(9)(2)][PF6](2) were prepared. (C) 2002 Elsevier Science Ltd. All rights reserved.