Ruthenium bipyridine

Recently the Nolte group has constructed a series of non-classical amphiphiles consisting of ruthenium-bipyridine centers functionalized with a receptor cavity viz., water-soluble metallo-hosts (Figure 7.22).15... 

This type of receptor is represented by compounds 16a,b bearing ruthenium ) bipyridine moieties. Both calixarenes [18] exhibit 1 1 binding of chloride and bromide anions (DMSO-d6), and they are especially suitable for the complexation of H2POj (X16a=2.8-104 M-1 K16b=5.2 103 M"1). On the other hand, if we compare these results with those for similar non-calixarene receptors, where the bipyridine unit is substituted by alkyl, aryl or ethylene glycol substituents, the introduction of calixarene does not bring any substantially new features into the complexation abilities of these derivatives. As shown by X-ray analysis, the anion is encapsulated within the cavity formed by amidic functions with the contributions of CH...anion interactions from the bipyridine unit. 

TOWARDS THE DESIGN OF MOLECULAR PHOTOCHEMICAL DEVICES BASED ON RUTHENIUM BIPYRIDINE PHOTOSENSITIZER UNITS. 

Introduction of another ruthenium bipyridine moiety or bridging metallocene (ferrocene, cobaltocenium) results in sensors that specifically bind chloride anions (Figure 16.15). The structural modification of the amide receptor results in a decease in cavity dimensions and significant rigidity of the macrocycle. Therefore it cannot accommodate hydrogen phosphate anions, but only much smaller CF [45, 46]. 

Organic synthesis via transition metal complex-catalyzed electrochemical and photochemical reduction of CO2 has been developed [2,122b, 145-147]. Among transition metal complexes, ruthenium bipyridine complexes show high catalytic activity a typical reaction is shown in Eq. 11.79. [Ru(bpy)2(CO)2] and [Ru(bpy)2(CO)Cl] efficiently catalyze the electrochemical reduction of CO2 to CO and HC02. The nature of the products is dependent upon the pH of the solution. A catalytic cycle involving [Ru(bpy)2(CO)]°, ]Ru(bpy)2(C0)(C02 )] and [Ru(bpy)2(C0)C02H] was proposed (Eq. 11.79) [1461]. 

Argazzi et al. followed that strategy to elaborate a nanocrystalline solar cell which incorporates a molecular dyad (HI) based on ruthenium bipyridine as a sensitizer and phenothiazine as a donor (Figure 19) [109]. 

Figure 19. Molecular dyad based on ruthenium bipyridine and phenothiazine [109],...

The DNA duplex formation can be detected based on the incorporation or association of a hybridization indicator or changes accrued from the hybridization event. Different indicators can be used in detection of DNA based on the appropriate electrochemical activity selected, it can be either label-free (e.g. guanine, adenine), or label-based (enz5nne-based, ferrous and ferricyanide. Ruthenium bipyridine [Ru (bpy)], methylene blue, Ethidium bromide etc). The hybridization event is detected via the increase or decrease in signal of the redox indicator or changes in conductivity or impedance/capacitance. 

A photoactive metal center is introduced in these systems. The ruthenium bipyridyl complexes are coordinated to the emeraldine base to form the corresponding polymer complexes as described above." The incorporation of the ruthenium centers to the pyridyl backbone has been also reported to give the ruthenium complexes Conjugated ruthenium bipyridine complexes thus obtained are evaluated to be photorefractive materials. Other transition metal complexes can be employed to form the corresponding polymer complexes. The pyridine unit is replaced by bithienyl, 1,4-diazabutadiene, ethylene, benzimidazole or thiazole. ... 

Spectroscopic techniques are used to probe the degree and rate of interaction between a molecule and a modified surface, most often as a model for chromatographic processes. For example, fluorescence spectroscopy has been used to determine the extent of interaction between a charged complex, ruthenium bipyridine, and both the silanols and a bonded organic moiety on a silica surface [55]. An example of the results obtained for bare silica, C-2 silica and C-18 silica at two pH values are shown in Figure 14. The data shows that... 

Figure 14. Normalized fluorescence of ruthenium bipyridine vs. its concentration on various silica surfaces. Top pH = 8.0 Bottom pH = 2.0 [55].

Photochemical Reduction of CO2 to HCOO Catalyzed by Ruthenium Bipyridine or Phenanthroline Complexes... 

Srimani D, BalaramanE, HuP, Ben-David Y, Milstein D (2013) Formation of tertiary amides and dihydrogen by dehydrogenative coupling of primary alcohols with secondary amines catalyzed by ruthenium bipyridine-based pincer complexes. Adv Synth Catal 355 2525... 

The conversion of boronic acids into phenols has been achieved using visible light catalysis (Scheme 2.32) [42]. hi addition to light, the catalyst components consisted of a ruthenium bipyridine species, an amine, and DMF. All the components were needed for a successful reaction since low conversions were observed if any of the components were absent. The ability to use air as the oxidant was one of the practical aspects of this chemistry. While a wide range of arylboronic acids were successfully transformed into phenols, a pinacol-derived arylboronate also served as a substrate in these reactions (up to 94% conversion). In addition to the ruthenium-catalyzed reaction, a metal-free version of die chemistry was also developed using an organic dye. 

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