Synthesis, Characterization, and Photophysical Studies of New Bichromophoric Ruthenium(II) Complexes

Abstract

The photophysical properties of a series of prepared ruthenium tris(bipyridine) complexes, covalently linked to aromatic species, of type [Ru(bpy)(2)-(4-methyl-4'-(arylaminocarbonyl)-2,2'-bipyridine)](2+) ([Ru(bpy)(2)(mbpy-L)](2+), where bpy = 2,2'-bipyridine; mbpy = 4-methyl-4'-carbonyl-2,2'-bipyridine; and L = 2-aminonaphthyl (naph), 9-aminoanthryl (anth), 1-aminopyrenyl (pyr), or 9-aminoacridinyl (acrd)) were studied by electronic absorption spectroscopy and steady state and time resolved luminescence spectroscopies. The absorption spectra of the MLCT electronic transition of the complexes are similar, which is in agreement with a practically constant redox potential of Ru(III/II) close to 1.28 V versus Ag/AgCl. However, the luminescence spectra of the new complexes are red shifted compared to Ru(bpy)(3)(2+), and this effect is ascribed to solvation and inductive effects of the amide group which enhance the symmetry breakdown among the three bipyridyl ligands. The energy stabilization of the (3)MLCT state is in the range 2.1-8.4 kJ/mol. The triplet-triplet energy transfer between the Ru complex and the aromatic species linked by an amide spacer is a slow process with rate constants of 2.6 x 10(4), 3.6 x 10(4), and 4.9 x 10(4) s(-)(1) for anthracene, acridine, and pyrene as acceptors in methanol, respectively. The energy transfer rate constant increases with decreasing polarity of the solvent. In dichloromethane, the rate constants for anthracene, acridine, and pyrene acceptors are 2.6 x 10(5), 1.5 x 10(5), and 2.9 x 10(5) s(-)(1), respectively. The low efficiency of energy transfer is due to the small difference in triplet energy between donor and acceptor species, weak electronic coupling, and unfavorable Franck-Condon factors, despite the short separation distance between donor and acceptor species in an amide bridge.

Ruthenium(II) bipyridine complexes with pendant anthracenyl and naphthyl moieties: A strategy for a ROS generator with DNA binding selectivity

“…2 (a), from 420 to 550 nm) besides the MLCT-based emission (centered at 646 nm) with lower intensity. These observations are consistent with direct emission of the anthracenyl group and with some singlet energy transfer or direct intersystem crossing (ISC) from the anthracenyl antennae to the Ru(II) core in accordance to the literature [22][23][24] and as shown in Scheme 1. The emission spectra of RuNaph, with excitation in the aryl group ( Fig.…”

Investigations on Photoinduced Interaction of 9-Aminoacridine with Certain Catechols and Rutin

“…However, there is also a minor component in the decay process (0.149±0.0020 relative amplitude) with lifetime of 5.4±0.5 ns. The obtained results found to be in agreement with the values, earlier report in the literature [20,21]. From Fig.…”

Photophysical properties of polyacrylic acid with Ru (II) polypyridyl complexes

“…The luminescence of the polymer-Ru systems in the presence of water-soluble quencher is studied by using the acridinium dyes as triplet acceptors in energy transfer process [16,17]. For comparative purpose, we have used [Ru(bpy) 3 ] 2+ complex solely adsorbed in PAA and PMAA aqueous solution.…”