Synthesis and characterization of ruthenium(II) complexes incorporating 4-phenyl-terpyridine and triphenylphosphine

The syntheses of two new series of ruthenium(II) complexes incorporating substituted 4-phenyl-terpyridine, triphenylphosphine, and chloride (A Series) or hydride (B Series) are reported. In both series 4-phenyl-terpyridine incorporated substituents of varying electronic character at the 4-position: 4-(4-chlorophenyl)-2,2:6,2-terpyridine (ClPh-tpy); 4-(4-nitrophenyl)-2,2:6,2-terpyridine (NO2Ph-tpy) and 4-(4-methoxyphenyl)-2,2:6,2-terpyridine (OMePh-tpy). The complexes have been characterized by elemental analysis and UV-vis, IR, and NMR spectroscopy and their electrochemical properties studied. The substituents on the 4-phenyl-terpyridine ligand influence the properties of the metal center. For all complexes prepared, (max) of a characteristic low energy band in the UV-vis spectrum was found to move to shorter wavelengths as the solvent polarity increased (a hypsochromic shift). For the B series complexes, the low energy band was broader and undergoes a small shift to lower frequencies as a result of the substitution of chloride by a hydride. The H-1 and P-31 NMR spectra clearly indicate that the geometry of the 4-phenyl-terpyridine ligand is meridional in the complexes, with the two triphenylphosphines trans to each other. Upon optimization of the experimental procedures the yields increased to 70% for the B series complexes.