Efficient energy transfer via the cyanide bridge in dinuclear complexes containing Ru(ii) polypyridine moieties

Abstract

We report the synthesis, structure and properties of the cyanide-bridged dinuclear complex ions [Ru(L)(bpy)(μ-NC)M(CN)(5)](2-/-) (L = tpy, 2,2';6',2''-terpyridine, or tpm, tris(1-pyrazolyl)methane, bpy = 2,2'-bipyridine, M = Fe(II), Fe(III), Cr(III)) and the related monomers [Ru(L)(bpy)X](2+) (X = CN(-) and NCS(-)). All the monomeric compounds are weak MLCT emitters (λ = 650-715 nm, ϕ ≈ 10(-4)). In the Fe(II) and Cr(III) dinuclear systems, the cyanide bridge promotes efficient energy transfer between the Ru-centered MLCT state and a Fe(II)- or Cr(III)-centered d-d state, which results either in a complete quenching of luminescence or in a narrow red emission (λ ≈ 820 nm, ϕ ≈ 10(-3)) respectively. In the case of Fe(III) dinuclear systems, an electron transfer quenching process is also likely to occur.

Emissive cyanide-bridged bimetallic compounds as building blocks for polymeric antennae

“…As previously observed, 9 . [19][20][21][22][23][24][25][26][27] The tetrapyridinic fragment of 7a r presents the usual propeller-like configuration 13,28,29 with an average tilting angle of 40°…”

“…(L = tpy (5a r ) or tpm (5b r )). These syntheses are a variation of those described in our previous work 9…”

“…The cyanide bridge promotes efficient mixing between the metal-centered states and opens the way for efficient electron and energy transfer. [7][8][9] Additionally, unlike other widely used bridges, the cyanide group does not introduce low energy states that may act as electron or energy traps. In a previous report 9 Table 1) which include second and third row transition metals, and therefore have their metal centered (MC) states at higher energies so they may not be able to quench the excited state.…”

Tris[4-(dimethylamino)pyridine][tris(pyrazol-1-yl)methane]ruthenium(II) bis(hexafluoridophosphate) diethyl ether monosolvate

“…For background to the synthesis, see: Llobet et al (1988); Calvert et al (1983). For examples of other structures of ruthenium complexes of the Tpm ligand, see: Llobet et al (1989); Wilson & Nelson (2003); Katz et al (2005); Iengo et al (2005); Foxon et al (2007); Kuzu et al (2009); Waywell et al (2010); Zagermann et al (2011); De et al (2011); Agarwala et al (2011Agarwala et al ( , 2013; Serrano et al (2011); Cadranel et al (2012). For examples of other structures of ruthenium complexes of the dmap ligand, see: Bonnet et al (2003); Rossi et al (2008Rossi et al ( , 2010; Mutoh et al (2010); Dunbar et al (2011).…”

“…Ruthenium complexes of the tris(1-pyrazolyl)methane (Tpm) ligand have been studied in a number of laboratories, and many examples have been structurally characterized (e.g. Llobet et al, 1989;Wilson & Nelson, 2003;Katz et al, 2005;Iengo et al, 2005;Foxon et al, 2007;Kuzu et al, 2009;Zagermann et al, 2011;De et al, 2011;Agarwala et al, 2011;Serrano et al, 2011;Cadranel et al, 2012;Agarwala et al, 2013). However, the only one featuring three pyridine (py) or pyridyl coligands is the complex salt [Ru II (Tpm)(py) 3 ][PF 6 ] 2 (Laurent et al, 1999), while [Ru II (Tpm)(dppz)(3-NH 2 py)] (Waywell et al, 2010) contains one chelating coligand.…”