THE COORDINATION CHEMISTRY OF MIXED PYRIDINEPHENOL AND PHENANTHROLINE-PHENOL LIGANDS - THE CRYSTAL-STRUCTURE OF 2-(2-HYDROXYPHENYL)-1,10-PHENANTHROLINE (HL) AND THE CRYSTAL-STRUCTURE AND PROPERTIES OF [FEL(2)][PF6]

The crystal structures of the N,N,O-terdentate ligand 2-(2-hydroxyphen yl)-1,10-phenanthroline (HL) and its Fe(III) complex [FeL(2)][PF6] (1) have been determined. In HL, an intramolecular O-H ... N hydrogen bon d between the phenolic OH and the adjacent nitrogen atom of the phenan throline fragment constrains these two donor atoms to be cisoid, with the proton 'chelated'. The molecules of HL are associated into pairs i n the crystal via a face-to-face aromatic pi-stacking interaction. Com plex 1 has a conventional distorted octahedral structure; sections of the aromatic ligands overlap between adjacent molecules to form an int erleaved stack. It is high-spin down to 83 K, and its EPR spectrum (fr ozen glass at 77 K) is entirely typical of a rhombically distorted hig h-spin Fe-III site.