Octahedral Fe(II) and Ru(II) complexes based on a new bis 1,10-phenanthroline ligand that imposes a well defined axis

A bis-chelating ligand (L1), made of two 7-(p-anisyl)-1,10-phenanthroline (phen) subunits connected with a p-(CH2)(2)C6H4(CH2)(2) spacer through their 4 positions, has been prepared, using Skraup syntheses and reaction of the anion of 4-methyl-7-anisyl-1,10-phenanthroline with alpha,alpha'-dibromo-p-xylene. Its Fe(II) complex, [FeL1(dmbp)](PF6)(2), was prepared in one step by reaction of L1 with [Fe(dmbp)(3)](PF6)(2) (dmbp = 4,4'-dimethyl-2,2'-bipyridine). On the other hand, its Ru(II) complex, [RuL1(dmbp)](PF6)(2), was prepared in two steps from Ru(CH3CN)(4)Cl-2 and L1, followed by reaction with dmbp. X-ray crystal structure analyses show that in the two octahedral complexes, ligand LI coils around the metal by coordination of the axial and two equatorial positions. It defines a 21 Angstrom long axis (O . . .O distance) running through the central metal and the terminal anisyl substituents. The complexes were also characterized by H-1 NMR, mass spectrometry, cyclic voltammetry, electronic absorption, and, in the case of Ru(II), fluorescence spectroscopy.