Energy Transfer in Rigid Ru(II)/Os(II) Dinuclear Complexes with Biscyclometalating Bridging Ligands Containing a Variable Number of Phenylene Units

Abstract

We have prepared rodlike cyclometalated Ru(II)/Os(II) dinuclear complexes, (ttp)Ru(dpb-(ph)(n)()-dpb)Os(ttp)(2+), where the biscyclometalating bridging ligands contain dipyridylbenzene fragments, dbp, separated by a variable number, n, of phenylene spacers, and the terminal ligand is a terpyridine derivative [dpbH is di-2-pyridyl-1,3-benzene, ttp is 4'-p-tolyl-2,2':6',2"-terpyridine, and n = 0-2]. The rigid bridging ligands keep the metal centers at a distance r(MM) = 11, 15.5, and 20 Å, depending on n. Photoinduced energy transfer has been investigated by luminescence spectroscopy in nitrile solvents at room temperature and at 77 K (i.e., in frozen medium). According to a classical description of the process, the energy transfer occurs in a nearly activationless regime, is governed by electronic factors, and can be described in terms of the Dexter-type mechanism. The obtained energy transfer rates roughly span 3 orders of magnitude and indicate (i) that the temperature (i.e., the state of the solvent) has a small influence on the process and (ii) that the interposed phenylene spacers are weak attenuators of intercenter electronic coupling, H [H = H(0) exp(-betar(MM)), with beta approximately 0.33 Å(-)(1)].

Providing power for miniaturized medical implants: triplet sensitization of semiconductor surfaces

“…Related, but much simpler, binuclear complexes have been used by many researchers [33][34][35] as a means ) 500 600 700 800 Figure 6. Overlaid absorption spectra recorded for the various mixed-metal complexes in BuCN at room temperature.…”

Molecular Materials and Devices: Developing New Functional Systems Based on the Coordination Chemistry Approach

“…Recently dyads and triads based on the photoactive, multibridging tris(bipyrazine)ruthenium(II) complex directly bound to transition metal complexes, have been generated 55 by following the coordination chemistry approach previously employed in the design of symmetric heptanuclear supermolecules, from [Ru(bpz) 3 ] 2+ (bpz = bipyrazine). [56][57][58] Such new systems contain a tris(bipyrazine) ruthenium(II) ion attached to bis(bipyridine) chlororuthenium(II)/(III) or pentacyanoferrate(II)/(III) complexes via a bipyrazine bridging ligand, e.g., [Ru(bpz) 3 Ru(bipy) 2 Cl] 3+/4+ or [Ru(bpz) 3 Fe(CN) 5 ] -/0 , as shown in Figure 10(A,B) (bipy = 2,2'-bipyridine).…”

Química de sistemas supramoleculares constituídos por porfirinas e complexos metálicos

“…Sauvage, Balzani e colaboradores 3,7,8,29,37,38 estudaram as propriedades de complexos binucleares de rutênio e ósmio (Figura 6) variando o número de fenilenos como grupos-ponte. Em nenhum dos complexos binucleares contendo ósmio pode-se observar a luminescência do complexo de rutênio.…”

“…Estudos fotofísicos mostraram que a luminescência do Ru(terpy) 2 é suprimida pela transferên-cia de energia para o complexo Os(terpy) 2 . Também, foi demonstrado que a transferência de energia ocorre quantitativamente pelo mecanismo de troca (Dexter), comprovando que os espaçadores do tipo fenileno são excelentes fios moleculares 3,38,39 . O mesmo comportamento foi observado mesmo quando aqueles sítios foram afastados por uma distância de cerca de 20 Å. Esses estudos foram estendidos para supermoléculas lineares contendo complexos de ródio e irídio.…”

“…Fita simples (acima) ou dupla (abaixo) de porfirinas 38 obtidas por automontagem coordenativa, respectivamente, de trans-mesodipiridilporfirina e meso-monopiridilporfirina ou meso-tetrapiridilporfirina e cis-meso-dipiridilporfirina com PdCl 2 Figura 12. Esquema mostrando o método de obtenção de porfirinas com substituintes 2,2:6,2-terpiridina e algumas supermoléculas obtidas por automontagem coordenativa reatividade, mas também pode provocar profundas alterações na solubilidade e nas interações intermoleculares.…”