Thermodynamically stable cages

Fig. 25 Solid state synthesis of thermodynamically stable cages 53 and 54, and representation of their X-ray-determined structures.139 (For color version of this figure, the reader is referred to the web version of this book.)...

We showed the possible existence of various forms of helically coiled and toroidal structures based on energetic and thermodynamic stability considerations. Though the formation process of these structures is not the subject of this work, the variety of patterns in the outer and inner surface of the structures indicates that there exist many different forms of stable cage carbon structures[10-19]. The molecules in a onedimensional chain, or a two-dimensional plane, or a three-dimensional supermolecule are possible extended structures of tori with rich applications. 

Thermal and/or photochemical electron transfer within the CT (precursor) complex generates the ion pair D, A as caged or freely diffusive ion-radicals. Most important from a synthetic point of view are the processes by which highly reactive ion-radicals undergo further irreversible transformation resulting in new (thermodynamically stable) products. In other words, the formation of the (precursor) CT complex and electron transfer act in tandem as a coupled set of pre-equilibria. The resultant ion-radical pair can undergo a subsequent (irreversible) transformation (with rate constant fcf) or back ET (Iibi t), which represent the basis for the ET paradigm and drive the coupled equilibria towards the products (P) [4], i.e. ... 

The uniqueness of boron is clearly seen in its elemental forms, the number and structural complexity of which exceed those of any other element. At least five distinct allotropes are known, all of which contain icosahedral B12 cluster units that in most cases are accompanied by other boron atoms lying outside the icosahedral cages. The most thermodynamically stable form, j8-rhombohedral boron, has 105 B atoms in its unit cell, while the /3-tetragonal phase has 192 atoms and is still not completely elucidated despite years of study ... 

Nucleation of hydrates with small guests (Xe, CH4, CO2) appear to involve mainly small cages. As well, the hydrate structures for CH4 and CO2 guests that appear after nucleation include not only the thermodynamically stable si hydrate, but also sll hydrate, which may be a kinetic product. This implies that it is not possible to predict the nature of the initial product after nucleating hydrate phases. Another point that can be made is that if the nucleation of hydrates with small guests involves small cages, there must be a... 

Formation of Tio and T12 cages might be the result of the decomposition of the Tg cage and re-assembling to thermodynamically similarly stable cages, as... 

The concluding fifth chapter touches upon the issues and advances in constructing of the most thermodynamically stable polysiloxanes built of cage-like subunits. The chemistry of siloxane cages has a long history, but their polymer biography is in the very beginning. 

X-ray diffraction and NMR studies have shown that metal fragments add exclusively across the [6,6] fusions to give rj2-type adducts. In contrast, organic derivatives add either to the [6,6] to form a closed adduct, or to the [6,5] fusions to form either an open or closed adduct (66). The ease with which some metal fragments dissociate off and on to the cage, in contrast to the organic derivatives, may explain the exclusive formation of the thermodynamically most stable [6,61-adducts. 

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