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)2C6H4(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 α,α‘-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)4Cl2 and L1, followed by reaction with dmbp. X-ray crystal structure analyses show that in the two octahedral complexes, ligand L1 coils around the metal by coordination of the axial and two equatorial positions. It defines a 21 Å long axis (O···O distance) running through the central metal and the terminal anisyl substituents. The complexes were also characterized by 1H NMR, mass spectrometry, cyclic voltammetry, electronic absorption, and, in the case of Ru(II), fluorescence spectroscopy.