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Amide functionalized bipyridine ligands and their ruthenium(II) complexes of the type [Ru(bipyridine)2(L)](PF6)2were synthesized and characterized by UV/Visible, emission, FTIR,1H NMR spectroscopies and elemental analysis. Thermal properties of the ruthenium(II) polypyridyl complexes have been investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques. These complexes show remarkable thermal stability at high temperatures under nitrogen atmosphere. The ruthenium(II) complexes show increasing fluorescence intensity in the presence of the amide groups. The increase of the emission intensity and quantum yield of the molecules may be attributed to the change of dipole moment of the amide group on electronic excitation. The effects of substituent (‒CH3, ‒OCH3, ‒COOC2H5, ‒COOH) on photophysical properties of molecules were correlated with the Hammett Substituent Constants. The molecules exhibit linear correlation for absorption and emission maxima. [ABSTRACT FROM AUTHOR]

Abstract: Two new orange-red emitting ruthenium complexes, [Ru(bpy)2(4,4′-bis(3-ethylheptyl)-2,2′-bipyridine)](PF6)2 and [Ru(bpy)2(4-dihexylmethyl-4′-heptyl-2,2′-bipyridine)](PF6)2 with branched alkyl side groups on the bipyridyl ligand have been synthesized and used as dopants in an organic light emitting device. The device that contains the complex containing the 4-dihexylmethyl-4′-heptyl-2,2′-bipyridine ligand 1.0 wt.% doped polymer blends of poly(vinylcarbazole) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazol as the emitting layer reached to a luminous efficiency of 7 cd/A, and a maximum brightness of 3824 cd/m2 with an electroluminescence spectral peak at 600 nm and Commission Internationale de L’Eclairage chromaticity coordinates of (0.57, 0.39). The swallow-tail alkyl substituent in this complex played a significant role in lowering the tendency to aggregate and presenting a better electroluminescence efficiency than that of the complex derived from the 4,4′-bis(3-ethylheptyl)-2,2′-bipyridine) ligand in a device. [Copyright &y& Elsevier]