Analog Chain

There has been a great deal of interest in the UV-visible spectroscopy of the polygermanes, particularly in comparison with the analogous chains that have silicon or tin backbones.41,42 Both conventional and Raman spectroscopy have been employed. One interesting observation is that the symmetrically disubstituted polyfdi- n - a I k y I g e n nanes) exhibit thermochromic transitions at temperatures below those of their polysilane analogues. Another is the conclusion that in poly(di-n-hexylgermane) the side chains adopt trans-planar conformations as in the polysilane counterpart. The two chains are also similar in that both backbones can, under certain circumstances, also adopt planar zig-zag conformations. 

The process of cleavage of PyroPyr ends with formation of a monomeric Pyr and its radical cation Pyr +. The latter was found to initiate a radical chain by oxidation of further PyroPyr [8, 13]. In DNA, however, an analog chain reaction... 

Analogous chain reactions proceed with the other dimers [Mn(CO)5]2 and [FeCp(CO)2]2 [311,312]. 

As DNA synthesis proceeds, nucleotides from the solution are added to the growing polynucleotide chain. Chain extension takes place without complication as long as the incorporated nucleotides are derived from dATP, dTTP, dGTP, and dCTP. If, however, the incorporated species is derived from a dideoxy analog, chain extension stops. Because the dideoxy species ddA, ddT, ddG, and ddC lack hydroxyl groups at 3, they cannot engage in the 3 5 phosphodiester linkage necessary for chain extension. Thus,... 

Sinkankasite, Mn (H20)4[Al(P03 0H )2(0H)](H20)2, is also based on the [M T 4)2 ] chain of Figure 18d, extending in the c-direction to give a repeat of 7 A. However, it is topochemically different from the analogous chain in overite and tancoite because one of the tetrahedron vertices is occupied by (OH), forming an acid-phosphate group. The chains are linked in the Z -direction (Fig. 21e) by (Mn 02 H20 4) octahedra to form a thick slab parallel to (100). These slabs stack in the a-direction (Fig. 2If) and... 

Different from analytical dynamic solutions, instantaneous distributions are derived to describe the polymer microstructure made at a particular instant in time during the polymerization. These distributions are snapshots of the polymer microstructure at a given moment during the polymerization. A classic instantaneous distribution used to describe the CLD of linear polyolefins and other polymers that follow analogous chain growth kinetics was developed independently by Schulz [79] and Flory [80, 81]... 

Extensive structure analyses were first carried out for the dimers depicted in Scheme 1 (CBA- , n = 9,10). The same techniques were applied to the main-chain polymer liquid crystals having analogous chain sequences (Scheme 2), leading to the conclusion that conformational characteristics of the spacer involved in the nematic state are essentially the same in both dimer and polymer liquid crystals [99]. The molecular scheme described previously has also been successf ully adopted in the analysis of the observed chemical shift and the dipolar coupling data of the dimer and trimer com-... 

Fig. 51. (top) The anti-SiSj analogous chain of irons edge-connected [R4N] tetrahedia in PtjNCI, (bottom) a projection of the crystal structure on (001) with only the Cl" and Cl" bridges exhibited. 

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