Bipyridine molecules

NiS4 core is conserved giving trans octahedral complexes, while with bidentate amines cis octahedral complexes are obtained. Linear bidentate amines can result in a ID chain like in compound (341) where 4,4 -bipyridine molecules bridge the square planar units. 

Using SERS, Brolo et al. [249] have studied the potential-dependent orientation of 2,2 -bipyridine molecules adsorbed on a... 

Bipyridine molecule has near planar geometry, the angle between pyridine rings is equal to 2.9°. At the same time. The least-squares plane of Bipy is inclined with respect to equatorail plane of Np coordination polyhedron by angle of 12.4°. The interesting feature of this stmcture is outer sphere nitrate ion that is... 

Fig. 33 Two heteromeric resorcin[4]arene-based assemblies (a) capsule involving two ca-vitand tetracarboxylic acids and four 2-aminopyrimidines and (b) capsule involving two molecules of tetramethylresorcin[4]arene and four 4,4-bipyridine molecules. Guest nitroben-zenes are shown in dark gray.

To investigate the role played by disorder connected with the asymmetric donors, we have prepared BIP(TCNQ)2 salt with symmetric and asymmetric bipyridine molecules shown in Fig. 1. An inherent feature of BIP molecules is that they can occur both in doubly ionized and in neutral form. In the salts we have investigated, the ratio of neutral and doubly ionized BIP is 1 1 this also corresponds to the TCNQ /TCNQ0 ratio. Thus the TCNQ chain is quarter filled. 

One of the molecules which plays a role in this field is depicted in Fig. 1.9. The luminescent species is the F.u ion which we met already above. It is surrounded by a cage containing molecules of bipyridine. The whole complex is called a cryptate and its formula is written as [Eu C bpy.bpy.bpy) ". The cage protects the Eu " ion against the (aqueous) surroundings which tries to quench the luminescence. If this cryptate is excited with ultraviolet radiation, the bipyridine molecules absorb the exciting radiation and transfer their excitation energy subsequently to the Eu ion which then shows its red luminescence. 

One of the most successful families is represented by a series of polymers built from the linkage of metallic carboxylate chains through 4,4 -bipyridine spacers [ 176]. As an example, the coordination polymer [Cu(C4H O )(4,4 -bpyifH O) ] is formed by the connection of chains of Cu(II) metal ions bridged by succinate ligands through 4,4 -bipyridine molecules. This 3-D framework shows weak ferromagnetic interactions and channels, in which the water molecules are located. 

The effect of solution pH on the magnitude of a.c. voltammetry peaks for cytochrome c at the 4,4 -bipyridine/gold electrode was studied in 0.02 M phosphate, 1.0 M NaC104 electrolyte. The a.c. peak current exhibited a maximum at pH 7 and decreased on either side of this value over the range pH 5 to pH 10. On the basic side the decrease is due to the cytochrome c State III to State IV conformational transition and the decrease on the acidic side was attributed to protonation of the adsorbed 4,4 -bipyridine molecules. A pK for the alkaline transition was given as 9.1 and it was noted to be close to the previously reported value of 9.3. However, this value is different from the values of 7.8 to 8.0 previously reported for perchlorate-containing solutions and the reason for this difference is not clear. 

The effect of the 4,4 -bipyridine/gold interface on the electron transfer reactions of cytochrome c is of considerable interest. The current view pictures 4,4 -bipyridine molecules adsorbed on the gold electrode in a perpendicular, end-on orientation, forming a monolayer. Cytochrome c molecules reversibly... 

Newkome and coworkers also examined a dendritic system in which bipyridine molecules, incorporated into the branches, were subsequently complexed to yield dendrimers containing ruthenium tris-bipyridyl moieties dangling from the dendritic arms. In the electrochemistry of these compounds, the metal centers, surrounded by a dendritic network, exhibited irreversible kinetic behavior, as is commonly found in such systems. On the other hand, there are three separately identifiable ligand-based reductions, each of the... 

Up to now, the examples presented for 2D supramolecular assemblies are based on one type of interaction between the building blocks. In addition, it is possible to make use of different intermolecular interactions to steer the arrangement of two or more components into well-ordered stractures. For linear polyaromatic bipyridine molecules deposited onto Cu(lOO), ID chains are formed with the... 

A major improvement in the STM procedure produced SPBJ histograms of STM currents (Figure 4) measured between an Au(lll) surface and an Au nanotip immersed in a 0.1-M NaC104 solution " when the gap is closed by an Au filament (Figure 4a,b) then maxima in the conductance can be seen near zero bias (V = 0.013 V), in units of the Landauer conductance quantum Gl = 2e /h (4) for one filament (Gl), two filaments in parallel (2 Gl), or three filaments in parallel (3 Gl). When the An filament is absent, but the solution is made 1 mM in 4,4-bipyridine (10), where bonds can be made between the Au electrodes and the two N atoms, then conductance maxima are seen at 0.01 Gl, 0.02 Gl, and 0.03 Gl this corresponds to a molecular resistance of 1.3 0.1MS2 per 4,4 -bipyridine molecule. As the bias is increased. 

Figure 42 Magnetic sensors. Two views of Mn3(4,4 -bipyridine)3(OH2)4][Cr(CN)6]2.2(4,4 -bipyridine)- 4(H20) highlighting (a) the pillaring by 4,4 -bipyiidine of the two-dimensional arrays comprising Mn + and Cr(CN)6 ions and (b) the square and distorted triangular channels, which are occupied by guest water and 4,4 -bipyridine molecules, respectively, but which are not shown. Removal of the guest molecules as well as coordinated water molecules results in a similar architecture that adsorbs gas molecules accompanied by ferromagnetic responses.

Physical cross-linking is easily incorporated into the structures of supramolecular side-chain polymers by using bi- or multifunctional molecules [9,31,93]. The complexation of the functionalized polyacrylates, a stilbazole, and bipyridine molecules form supramolecular side-chain cross-linked polymer 37 (Figure 27) [31,93]. Bis-imidazolyl compounds are also used for such cross-linking [105]. Reversible association-dissociation of the hydrogen bonding leads to the reversible thermal order-disorder transitions, which is an important feature of supramolecular materials. Liquid-crystalline main-chain supramolecular networks have been prepared from multifunctional components [32,123-126], which will be described in Section IV. 

The incorporation of bipyridine molecules coordinated to transition metals into the sidechains of polymers has also been utilized to tune the electronic and optical properties of polymers. " Frechet and coworkers synthesized polymers incor-... 

H. Shimin, Z. Jiaxing, L. Rui, N. Jing, H. Rushan, S. Ziyong, Z. Xingyu, X. Zenquan and W. Quande, First-principles calculation of the conductance of a single 4,4 bipyridine molecule. Nanotechnology, 2005,16, 239. 

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