Terpyridine complexes

Ru-Os-bis(2,2 6, 2") terpyridine complexes attached to biphenyl spacer groups [273] and the electron transport characteristics of ferrocene covalently bound to OPE rods [274] or oligoaniline junctions [275]. 

Although there have been numerous reports of nickel(II), palladium(II), and platinum(II) complexes of 2,2 6, 2"-terpyridine, complexes in higher oxidation states are all but unknown. Morgan and Burstall described the... 

Constable, E.C., Harverson, P., Smith, D.R. and Whall, L.A. (1994) 4-tert-Butylphenyl solubilised oligopyridines Tetrahedron, In the press Armaroli, N., Balzani, V., Constable, E.C., Maestri, M. and Cargill Thompson, A.M.W. (1992) Ligand substitution patterns control photophysical properties of ruthenium(II)-2,2 6, 2"-terpyridine complexes - room temperature emission from [Ru(tpy)2] analogues Polyhedron, 11,2707-2710... 

A competitive assay (indicator displacement assay, IDA) was reported by Anslyn using the Zn(II) complex 49 shown in Figure 21. This 2,2 6,2"-terpyridine complex forms a chemosensing ensemble with pyrocatechol violet because of the ability of the dye to chelate the Zn(II) cation. On addition of a series of unprotected amino acids to a solution of the chemosensing ensemble, the release of the dye was visually verified and spectroscopically measured (1 1... 

Figure 2.30. Binuclear Ru" bis(2,2 6, 2"-terpyridine) complexes built around a polytopic ligand with variable geometry.

Si. rra(pentafluorophenyl)boron was found to be an efficient, air-stable, and water-tolerant Lewis-acid catalyst for the allylation reaction of allylsilanes with aldehydes.167 Sc(OTf)3-catalyzed allylations of hydrates of a-keto aldehydes, glyoxylates and activated aromatic aldehydes with allyltrimethylsilane in H2O-CH3CN were examined. a-Keto and a-ester homoallylic alcohols and aromatic homoallylic alcohols were obtained in good to excellent yields.168 Allylation reactions of carbonyl compounds such as aldehydes and reactive ketones using allyltrimethoxysilane in aqueous media proceeded smoothly in the presence of 5 mol% of a CdF2-terpyridine complex (Eq. 8.71).169... 

The solution chemistry and water oxidation of a trinuclear complex [(bpy)2(H20)RuIIIORuIV (bpy)20Ruln(OI I2)(bpyh]6+ 489 and of a (nonisolated) binuclear Ru -terpyridine complex [ (terpy)(H20)2Rum 20] f+ 490 have also been reported. However, these complexes, as well as mononuclear [Ru(bpy)2(H20)2]2+,491 arenotcatalystsasaconsequenceoftheirfastdecomposition. 

Perrine TM, Dunietz BD (2008) Conductance of a cobalt(II) terpyridine complex based molecular transistor a computational analysis. J Phys Chem A 112 2043-2048... 

Redox molecules are particularly interesting for an electrochemical approach, because they offer addressable (functional) energy states in an electrochemically accessible potential window, which can be tuned upon polarization between oxidized and reduced states. The difference in the junction conductance of the oxidized and the reduced forms of redox molecules may span several orders of magnitude. Examples of functional molecules used in these studies include porphyrins [31,153], viologens [33, 34,110,114,154,155], aniline and thiophene oligomers [113, 146, 156, 157], metal-organic terpyridine complexes [46, 158-163], carotenes [164], nitro derivatives of OPE (OPV) [165, 166], ferrocene [150, 167, 168], perylene tetracarboxylic bisimide [141, 169, 170], tetrathia-fulvalenes [155], fullerene derivatives [171], redox-active proteins [109, 172-174], and hydroxyquinones [175]. 

In these cases, there is the expected tetragonal distortion due to the Jahn-Teller effect in addition to the often mentioned octahedral distortion associated with polypyridine complexes. For the terpyridine complex there is the usual difference between the distances separating the metal and nitrogen atom of the central pyridine and that of the metal and the nitrogen atom of the peripheral pyridines. 

Bailey JA, Miskowski VM, Gray HB. Spectroscopic and structural properties of binuclear platinum-terpyridine complexes. Inorg Chem 1993 32 369-370. 

Figure 10.8 shows the example ofa ruthenium(ii) bis-terpyridine complex that acts as the scaffold for a biscarboxylate recognition site 22 [62]. 

Finally, a very simple molecular electronic component is benzene-1,4-dithiol, which is readily used as a linker between gold electrodes in the same way as the cobalt terpyridine complex shown in Figure 11.40. Benzene dithiol has been used to demonstrate the thermoelectric effect in molecular electronic systems as a linker between a gold surface and the gold tip of a modified atomic force microscope. Thermoelectricity (termed the Seebeck effect) is the generation of an electrical potential... 

A further contribution from this group, in collaboration with Pikramenou, deals with energy transfer processes in self-assembled structures of multin-uclear complexes. Each ligand of a Ru(bpy)32+ unit is connected to the rim of a /1-cyclodextrin receptor to form Ru(/J-CD-mbpy), which can complex in a polar medium the biphenyl (or adamathyl) tail of an Ir(III)-terpyridine complex, Fig. 24c [131]. In order to provide complexation of the Ir guest and because of the low association constant, a consistent excess of the Ru(/J-CD-mbpy) host is required, (80-90% of host relative to guest). Under these... 

Further examples of energy transfer processes in assemblies involving Ir(III) polyimine derivatives, from Williams et al., are shown in Fig. 25b and c [133]. These are bimetallic assemblies containing Ir and Ru centers, either an Ir(terpy)23+ connected to a Ru(bpy)32+ via a polyphenyl bridge, Fig. 25b, or a Ru(terpy)22+ connected to an Ir(ppy)2bpy+ moiety, Fig. 25c. Energy transfer occurs in both arrays in the direction Ir->- Ru, but whereas for (b), Fig. 25, the sensitized luminescence of the Ru center upon excitation of the Ir center can be detected also at ambient temperature, in array (c) the sensitized luminescence of the Ru(II)-terpyridine complex can only be revealed at low temperatures (165 K), due to the well-known non-emissive nature of Ru(terpy)22+ at room temperature. 

The metal-to-ligand coordination coupling chosen for the construction of a family of giant amphiphiles was that of a metal-terpyridine complex, which is known to form stable bis-complexes with a variety of transition-metal ions.275 The versatility of this metal-to-ligand system has been recently demonstrated in the construction of a series of coordination polymers and block copolymers.276... 

The synthesis of 2,2 6, 2"-terpyridine was first described by Morgan and Burstall in 1931.19 Subsequently, metal-terpyridine complexes have become an area of active research. In 1995, Constable proposed a concept of using terpyridine functionalized monomer to give coordination polymers upon addition of metal ions (Fig. I).8... 

Early Work on Systems Based on Ru(ll) and Os(ll) bis-Terpyridine Complexes... 

Barigelletti F et al (1993) Luminescence properties of rigid rod-like binuclear ruthenium(II)-osmium(II) terpyridine complexes - electronic interaction through phenyl bridges. JCS Chem Commun 942-944... 

Ding H-Y, Wang X-S, Song L-Q, et al. Aryl-modified ruthenium bis(terpyridine) complexes Quantum yield of 02 generation and photocleavage on DNA. J Photochem Photobiol A Chem 2006 177 286-94. 

Os and Ru bis(terpyridine) complexes have been covalently linked (Figure 13) and their electrochemical, absorption spectra, photochemical and photophysical properties have been studied. The strong electronic interaction decreases as the one or two phenylene spacers are added but remains large enough to allow fast electron transfer. ... 

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