Designing novel Sn-Bi, Si-C and Ge-C nanostructures, using simple theoretical chemical similarities.
Bottom Line:
When successful, these concepts are very powerful and transparent, leading to a large variety of nanomaterials based on Si and other group 14 elements, similar to well known and well studied analogous materials based on boron and carbon.Some of the so called predicted structures have been already synthesized, not necessarily with the same rational and motivation.Finally, it is anticipated that such powerful and transparent rules and analogies, in addition to their predictive power, could also lead to far-reaching interpretations and a deeper understanding of already known results and information.
Affiliation: Department of Physics University of Patras, GR 26500, Patra, Greece. zdetsis@upatras.gr.
ABSTRACT
A framework of simple, transparent and powerful concepts is presented which is based on isoelectronic (or isovalent) principles, analogies, regularities and similarities. These analogies could be considered as conceptual extensions of the periodical table of the elements, assuming that two atoms or molecules having the same number of valence electrons would be expected to have similar or homologous properties. In addition, such similar moieties should be able, in principle, to replace each other in more complex structures and nanocomposites. This is only partly true and only occurs under certain conditions which are investigated and reviewed here. When successful, these concepts are very powerful and transparent, leading to a large variety of nanomaterials based on Si and other group 14 elements, similar to well known and well studied analogous materials based on boron and carbon. Such nanomaterias designed in silico include, among many others, Si-C, Sn-Bi, Si-C and Ge-C clusters, rings, nanowheels, nanorodes, nanocages and multidecker sandwiches, as well as silicon planar rings and fullerenes similar to the analogous sp2 bonding carbon structures. It is shown that this pedagogically simple and transparent framework can lead to an endless variety of novel and functional nanomaterials with important potential applications in nanotechnology, nanomedicine and nanobiology. Some of the so called predicted structures have been already synthesized, not necessarily with the same rational and motivation. Finally, it is anticipated that such powerful and transparent rules and analogies, in addition to their predictive power, could also lead to far-reaching interpretations and a deeper understanding of already known results and information. No MeSH data available. Related in: MedlinePlus |
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Mentions: The BH→Si boron connection has originated from the fluxionality and similarity of magic silicon clusters (and, in particular, of the controversial Si6 cluster [11-13]) with the corresponding deltahedral boranes. It was shown initially [11,12] that the Si62- dianion and the corresponding isovalent B6H62- borane have exactly the same geometrical and electronic structure (including the frontier orbitals) as shown in Figure 3 and they are, therefore, isolobal and homologous. Furthermore, through the BH1-→CH (2) or 2BH1-→ 2CH substitution, the validity of which is established through the synthesis and stability of the well-known C2B4H6 (and, in general, of C2Bn-2Hn) carborane, we can assume the isolobal equivalence Sin-2C2H2⇔C2Bn-2Hn (10) between neutral hydrogenated silicon carbon clusters and deltahedral carboranes [10-15]. The same is true for Sin-4C4H4 clusters and C4Bn-4Hn carboranes (namely Sin-4C4H4⇔C4Bn-4Hn), as illustrated schematically in Figure 4. Applying the isolobal analogy (10) to existing organometallic multidecker sandwiches [30-33] we have designed (in-silico) analogous organometallic silicon- carbon sandwiches[16] which, as shown in Figure 5, are fully homologous (isolobal) to the carborane prototypes and are, therefore, expected to have similar chemical and technological properties. Apparently similar results should be able to be obtained for germanium-based multidecker sandwiches, since Si and Ge structures are fully homologous and isolobal and the Si→Ge substitution rule is valid almost everywhere. This is equivalent to the BH→Ge substitution, which seems to be more valid compared to the BH→Si substitution, in particular for larger clusters [12,13]. This is related to the fact that the BH→Si (1) is based on the much stronger BH2-→Si2- substitution between dianions [10,11] from which the equivalence Sin-2C2H2⇔C2Bn-2Hn is obtained by the well-tested substitutions Si1-→CH and BH1-→CH, respectively. It is the BH2-→Ge2- relation which is much more valid when compared to the BH2-→Si2, mainly due to the inert pair effect [14,15]. For exactly the same reason, as we go down the 14th column of the periodical table (see Figure 2), the BH2-→Sn2- relation is even more valid than the BH2-→Ge2-, which is verified experimentally by the recent synthesis of stannaspherene, Sn122- (see Discussion section) [14,15,22]. |
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Affiliation: Department of Physics University of Patras, GR 26500, Patra, Greece. zdetsis@upatras.gr.
No MeSH data available.