Polysilanes and polygermanes

Biynda et al. (1993) measured photogeneration efficiencies of PMPS doped with acceptor molecules with different reduction potentials. Acceptor doping increased the phologeneration efficiencies by as much as a factor of 10, but decreased the mobilities. The increase in efficiency scaled with decreasing reduction potential. 

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SCHEME 2. Photoinduced electron transfers from polysilane and polygermane to Cgo... 

Nonlinear Optical Properties of Substituted Polysilanes and Polygermanes... 

Recent studies of polymeric Group IV catenates (in particular, polysilanes and polygermanes, la,b have demonstrated that there is significant sigma electronic delocalization along the polymer backbone which is responsible for many of the curious electronic properties of this class of materials [3]. 

M-M bonds in polysilanes and polygermanes as well as silylgermanes are readily cleaved by photolysis to generate reactive silylenes and germylenes which are trapped with butadienes affording the cyclic products 155 and 156 <20000M3232, 2002JOM(649)25>. In the case of 156, the replacement of At by less bulky substituents leads to small yields and the cycloaddition is accompanied by the formation of many side products. 

C-O bond cleavage is most efficiently set up in strained systems, e.g. in oxiranes [26] and oxetanes [27], whereas 0-0 bond cleavage in cyclic peroxides [28] and C-S [29] and C-Se [30] bond rupture occur efficiently even in unstrained compounds. Si(Ge)-Hal bond cleavage [31] has become a valuable reaction, e.g. in the preparation of network polysilanes and polygermanes [32]. 

The usual procedure in preparations of polysilanes and polygermanes is to circulate the simple hydride through an ozonizer-type discharge until practically all of it has decomposed and the gas being circulated is principally hydrogen. The product hydrides are trapped out in a suitable cold trap in the gas circuit. If the desired product vapors were allowed to circulate continually through the discharge, the product would... 

Band structure calculations have also been reported for hypothetical polystannanes 6.4 (R=R =H), and the results have been compared with those for analogous polysilanes and polygermanes [15]. The band gap (Eg) was calculated to decrease in the... 

Baumert JC, Bjorklund GC, Jundt DH, Jurich MC, Looser H, Miller RD, Rabolt J, Soorijakumaran R, Swalen JD, Twing RJ (1988) Temperature dependence of the third-order nonlinear optical susceptibilities in polysilanes and polygermanes. Appl Phys Lett 53(13) 1147-1149... 

ABSTRACT. Band calculated results for electronic structures of sigma-conjugated polymers are reviewed. Conformational and substitutional effects for polysilanes are calculated theoretically and are discussed in the light of experimental data from UV absorption and photoluminescence. The electronic structures of hetero-copolymers of polysilane and polygermane, corresponding to the 1-dimensional superlattice structure, are described. Two-dimensional silicon network polymers are studied theoretically and experimentally. 

Figure 1. Polycyclic polysilanes and polygermanes prepared via reductive coupling of RMX3 or RX2M-MX2R...

Although polysilane and polygermane do not fill the requirements of having an extensively delocalised 7r-electron system along the backbone, they demonstrate remarkably high THG effects coupled with high transparency and ease of processing (Fig. 4.24). Films of polysilane [136] between 0.15 and 0.45//m in thickness have been measured [135]. Transparent down to 450 nm, they have = 1.5 x 10 esu at 1.064 //m,... 

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