Rigid-rod polyynes

Use of similar synthetic methodologies as above leads to the generation of rigid-rod polyynes containing extended spacer units (Fig 8.37) [67]. 

Although rigid-rod polyynes are still being investigated some of their properties in general and those of the platinum polyynes in particular are beginning to be unraveled. These can be summarized as follows ... 

The absolute moleeular weights of these materials have been established by GPG by means of the universal calibration technique that involves the acquisition of intrinsic viscosity data. As with the aforementioned platinum polyyne polymers 166 (M = Pt(P"Bu3)2 x = Z), the intrinsic viscosities were found to be independent of the nature of the solvent and a Mark-Houwink a-value of 1.5 was determined, which is indicative of a rodlike structure. Interestingly, it was found that in this case, GPG, using PS standards, underestimates the true molecular weight of the polymers. This was attributed to the high molar mass of a repeat unit in the Ni polymer 207 compared to PS, which overcompensates for the effect of the rigid-rod structure that would be expected to lead to the opposite situation. Absolute values of of up to ca. 1 x 10 were determined for the polymer samples. 

Rigid-Rod Transition Metal Acetylide Polymers 1171 Table 5.4 Third-order nonlinear optical coefficients for some Pt-polyynes [84]... 

The metal-containing polyynes are an interesting class of main-chain organometallic polymers that have been under investigation since the 1970s. These systems are known for their rigid-rod stractures and electronic communication over the extensively... 

The third class of polymers that we will investigate in this chapter is polyynes which are prepared by the involvement of acetylene fimctional groups in the polymerization reaction. These polymers are also called rigid-rod organometallic polymers. In these types of polymers various late transition metal ions alternate with a rigid organic unit. 

Fig. 8.37. Rigid-rod platinum (II) polyynes containing long spacer units...

Another approach for the preparation of Ni(II)-containing rigid-rod polymers involves a ligand exchange reaction. Thus, the reaction of the iram -Ni(PnBu3)2(C H)2 with an aryl diacetylene leads to the elimination of acetylene and formation of a Unear polymer (Fig. 8.46) [3]. Other types of polyynes include Au(I)-containing rigid-rod polymers [4]. 

The interest in transition metals with <7-bound alkynyl ligands continues, since metal acetyiides are potential nonlinear optical, conducting, or liquid crystalline materials. Their chemistry and applications have been reviewed in 2003 and 2004. Another review dealing on organoiron polymers includes also rigid-rod iron acetyiides. " The chemistry of metal complexes with 1,3-diynes and polyynes was surveyed in 2001. " ... 

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