Intramolecular Energy Transfer in Covalently Linked Polypyridine Ruthenium(II)/Osmium(II) Binuclear Complexes. Ru(II)(bpy)2Mebpy– (CH2)n–MebpyOs(II)(bpy)2 (n=2, 3, 5, and 7)

Abstract

A novel series of polymethylene-linked heterobinuclear complexes of polypyridine ruthenium(II)/osmium(II) complex Ru(II)(bpy)2Mebpy–(CH2)n–MebpyOs(II)(bpy)2(bpy=2,2′-bipyridine and n=2, 3, 5, and 7), 1, was prepared. The photophysical behavior was examined in various solvents. The emission spectra of 1 (excitation wavelength: 455nm) showed a nearly complete quenching of RuII→π*(bpy) metal-to-ligand charge transfer (MLCT) emission and the enhancement of OsII→π*(bpy) MLCT emission. The luminescence lifetime measurements by a time-correlated single photon-counting method provided evidence that intramolecular energy transfer is a significant pathway for the observed emission quenching. The rate constants of the intramolecular energy transfer in ethanol are 5.3×108, 3.3×108, 1.3×108, and 1.0×108s−1 for 1(n=2, 3, 5, and 7), respectively. They were found to be proportional to the inverse sixth power on the center-to-center distance of the two complexes. The mechanism is discussed in terms of the Förster (a dipole-dipole interaction) mechanism.

Characterization of excited electronic and vibronic states of platinum metal compounds with chelate ligands by highly frequency-resolved and time-resolved spectra

“…Moreover, Os(II)-bipyridine complexes represent suitable building blocks in connection with Ru(II)-polypyridine compounds for supramolecular systems [278,279] [280][281][282][283]. The importance of such processes was also emphasized more than a decade ago [35,36,126].…”

The influence of bridging ligand electronic structure on the photophysical properties of noble metal diimine and triimine light harvesting systems

“…Diimine and triimine complexes of Ru(II) typically absorb between 420 and 500 nm, often exhibit strong room temperature luminescence in the red and decay to the ground state via a 3 MLCT state with lifetimes that vary between a few nanoseconds to a few microseconds (Kalyanasundaram 1982;Juris et al 1988;Scandola and Indelli 1988;Krausz and Ferguson 1989;Nagle and Roundhill 1992;Vlcek 1998;Endicott et al 2002a, b). Finally, Os(II) imine complexes have absorption maxima for the spin allowed MLCT absorption at wavelengths similar to Ru(II), but also exhibit the spin forbidden 1 GS to 3 MLCT state absorption at longer wavelengths (Kober et al 1984(Kober et al , 1986Schanze et al 1986;Furue et al 1991;De Cola et al 1992;Belser et al 1995). The Os(II) complexes generally exhibit emission from the 3 MLCT state at longer wavelengths and with much lower efficiencies than corresponding Ru(II) complexes.…”

Electronic Conduction in Photoactive Metallo‐wires

“…In such systems, electronic energy transfer takes place by way of diffusional encounter between the terminals and involves Förster-type coulombic interactions. The rate of triplet energy transfer is only weakly dependent on the length of the bridge [83]. It should be noted that there is reasonable spectral overlap between emission from the Ru-based donor and absorption by the Os-based acceptor that favors the Förster mechanism.…”

“…In Fig. 2.8-2.10 are shown selected Ru/Os complexes where the bridging ligand is flexible (e.g., complexes 12 and 13) [83,84], semi-rigid (e.g., 14) [85], hybrid (e.g., 15 to 17) [86][87][88], or rigid (e.g., 18 to 20) [89][90][91]. The flexible hydrocarbon chain ( Fig.…”