Oligomers, defined length

Yao, J., Lowary, P.T., and Widom, J. (1990) Direct detection of linker DNA bending in defined-length oligomers of chromatin. Proc. Natl. Acad. Sci. USA 87, 7603-7607. 

The validity of the Forster theory was tested and confirmed in a number of model studies with compounds that contained a donor and an acceptor separated by well-defined rigid spacers. This work has been reviewed 5] In a classical study, a naphthyl group (donor) was attached to the C-terminal and a dansyl group (acceptor) to the N-terminal of poly-L-proline oligomers (1-12 proline residues) 61 These proline oligomers assume a trans helical conformation in ethanol and thus represent spacers of well-defined length (12-46 A). A continuous decrease in the transfer efficiency from 100% at a donor-acceptor separation of... 

In conjugated oligomers or polymers the backbone is longer and the end groups are less important. The term oligomers is normally used for shorter polymers with well defined length or number of monomer units. Typical examples of conjugated polymers are shown in Fig. 15. 

Even though the octayne derivative marked the longest linear diphenylpolyacetylene, multiple phenylacetylene scaffold topologies were developed in the following decade. Representative examples include carbon rods 67 and 68 produced by Misumi in 1961 (Fig. 1.5b) [60], Misumi and coworkers also produced several mixed hybrid scaffolds combining ethenyl and ethynyl spacers, such as 69 (Fig. 1.5b) as well as conformational isomeric ethenyl rods, such as 70, in 1962 [61]. Meier further discusses defined-length carbon-rich oligomers in Chapter 11, and the use of carbon-rich molecules as molecular wires is presented by Harriman and Ziessel in Chapter 2. 

Defined-length Carbon-rich Conjugated Oligomers... 

The exactly defined length of such oligomers is due to the monodisperse character of the compounds having an exactly defined number of repeat units n. Moreover, the distance L between the terminal positions of the conjugated system can be described as a linear function of n, provided that conformational effects do not considerably affect the extent of the oligomeric molecules. Scheme 11.2 illustrates L(n) for the series of oligo(l,4-phenyleneethynylene)s (OPE) 1 and oligo(l,4-phenylenevinylene)s (OPV) 2. 

I 7 7 Defined-length Carbon-rich Conjugated Oligomers n.3.3... 

Conjugated oligomers, which consist of CC double or triple bonds and/or 1,4-phenylene units, form rigid rods with a well defined length L. The extent of the chromophores/electrophores can be calculated by linear functions L n), where n is the number of repeat units. Scheme 11.24 gives a survey of such oligomers with k, I, m = 0,1. Many more conjugated series can be conceived with k,l,m> 1... 

Model compounds of laddo polymers are generally much better characterized and have some unique properties of their own. Oligomers of polyacenequinones have been reported as "moleciilar lines" since they are so rigid and can be synthesized with well-defined lengths. Related oligomers have been shown to form oriented Langmuir-... 

As a simplification, it was assumed that the interactions between charged oligomeric segments were negligible. These redox data correlate well with potential values obtained by extrapolation from quantum ma hanical calculations and redox potential measurements on oligomers of defined chain length. As expected,... 

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