Bonded Chain Structure

Fig. 3. The hydrogen-bonded chain structure of (2-morpholinoethyDdiphenylsilanol with the hydrogen atoms omitted for clarity. Drawn using coordinates taken from the Cambridge Crystallographic Database. 

Fig. 2 Linear hydrogen bonded chain structure formed between [18]crown-6 and [Cu(NH3)4 (H20)P [21]...

Fig. 3 Helical hydrogen bonded chain structure formed between [15]crown-5 and [La(N03)3 (H2O)2(l,10-phenanthroline)].[24]... 

A ferris wheel assembly involving a 1 1 complex of 19 and metallated [18]crown-6 is found in the cationic supermolecule [La(H20)3([ 18]crown-6)] (19+2H) + [48]. The lanthanum ion is coordinated by one calixarene sulfonate group, the [18] crown-6 and three aquo ligands, and the metallated crown sits inside the calixarene cavity. A helical hydrogen bonded chain structure is formed between the cationic assembly, water and chloride ions. The ferris wheel structural motif is also found in Ce3+ complex which simultaneously contains a Russian Doll assembly [44]. 

Fig. 11 Linear 1D hydrogen bonded chain structure of (C-methylcalix[4]resorcinarene).2 (4,4 -bipyridine)(4-bromobiphenyl) [57]... 

Fig. 25 The hydrogen bonded chain structure in complex [ Mo3S4(H20)7Cl2 2Hg](5)Cl4.14H20 where [ Mo3S4(H20)7Cl2 2Hg]4+ clusters are sandwiched between host 5 molecules [102]... 

Metal ions having coordination number two occur in Hg(CN)2, [Ag(CN)2]- and [Au(CN)2]-, all derivatives of d ° species in each case the structure is linear. In K[Cu(CN)2] the copper atom is actually three-coordinated, the anion being an infinite chain each copper has a carbon atom of an unshared cyanide, and a carbon atom and a nitrogen atom of shared cyanides, as nearest neighbours in approximately planar coordination. Three-coordination also occurs in the [Hg(CN)3]- ion, but there are weak interactions between two of the nitrogen atoms and mercury atoms of other anions, giving rise to a loosely bonded chain structure. 

Figure 8.48 The symmetry unique portion of the infinite co-crystal hydrogen-bonded chain structure of [U02C12(H20)3]16-([15] crown-5) 16.76...

FIGURE 1. Hydrogen bonded chain structures in simple siloxanediols. Curves represent Si—O—Si backbone, dashed lines show hydrogen bonding... 

It is helpful to use a more restrictive definition that classifies polymers as those materials which are based on covalently bonded chain structures formed by repetition of similar units, in which the chains are of sufficient length to confer on the material some additional properties not possessed by the individual units. Some of these properties are morphological and have a considerable bearing on structure-conductivity relationships in polymer electrolytes, as will be discussed later. 

Fig. 19. Calculated electron energy dispersion curve for Si(lll) in the energy optimized TT-bonded chain structure. The experimental points have been shifted upwards by 0.3 eV so that the theory and experiment are aligned at the J point. (after Ref. 59)... 

The realization of the structure of polymers is not very old. It was only in 1920 that Staudinger [10 to 12] began to argue that many synthetic and naturally occurring materials had long covalently bonded chain structures. An understanding of mechanisms of polymer synthesis only came about in the 1930s with the work of Carothers [13 to 15], Dostal and Mark [16], Flory [17], and others. 

Each of the surface atoms 1 or 2 is bonded to two other surface atoms 2 or 1, respectively. A zigzag chain of tt-bonded surface atoms directed along the [-110] direction is formed, resulting in a (2x1) reconstruction of a (111) surface. The resulting (2 x 1) jr-bonded chain structure is shown in Figure 9.21c and is observed both for Si(lll) and Ge(lll) surfaces after cleaving. 

The above-mentioned (2 x 1)jt-bonded chain structure is not the lowest energy surface on Si(lll) and Ge(lll) on annealing above 300°C, the Si(lll)-(2 X1) cleavage structure converts irreversibly into a (7 x 7) structure, which is the thermodynamic ground state of the clean Si(lll) surface up to 850°C [47]. Then the (7x7)-structure undergoes a first-order phase transition with Tc = 1135 K to... 

The surface energy of the (7x7) structure has been calculated by density functional theory and is 0.30eV per (1x1) cell lower than that of an ideal buLk-terminated Si(lll) surface and 0.06eV per (1x1) cell lower than that of the (2 X 1)7T-bonded chain structure. 

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