Paramagnetic Ru(III) complexes of tridentate ligands: Characterization of useful intermediates for heteroleptic Ru(II) complexes

Paramagnetic Cl3Ru(L) complexes of tridentate ligands (2a: L = 1a = 4′-(p-bromophenyl)-2,2′:6′,2″-terpyridine; 2b: L = 1b = 6-(p-bromophenyl)-2,4-dipyrid-2-yl-1,3,5-triazine) were synthesized in a high-yield method with facile isolation of these useful synthons. The complexes were isolated in high purity and were characterized by several methods, including standard techniques such as 1H NMR and electrospray ionization mass spectrometry. The 1H NMR of the complexes displayed peaks from + 10 to − 37 ppm, with the protons ortho to the nitrogen atoms coordinated to the paramagnetic centre being shifted the most (2a: H6,6″ = − 35.3 ppm; 2b: H6,6″ = − 26.1 ppm), while the protons on the non-bonding phenyl rings were relatively unchanged with respect to their uncomplexed ligands. The electronic absorption spectra of the complexes displayed both 1LMCT bands (Cl-to-Ru, 2a: λmax = 405 nm; 2b: λmax = 420 nm) and 1MLCT (Ru-to-L, 2a: λmax = 486 nm; 2b: λmax = 567 nm) bands. Due to the ease of purification and high yields, the use of complex 3, first introduced by Chatt, is the method of choice to form Cl3Ru(L) complexes of tridentate ligands.