Topological bond

In this chapter the symmetry properties of atomie, hybrid, and moleeular orbitals are treated. It is important to keep in mind that both symmetry and eharaeteristies of orbital energetics and bonding "topology", as embodied in the orbital energies themselyes and the interaetions (i.e., hj yalues) among the orbitals, are inyolyed in determining the pattern of moleeular orbitals that arise in a partieular moleeule. 

Mezey, P.G. (1995) Density domain bonding topology and molecular similarity measures., In Topics in Current Chemistry, Vol. 173, Molecular Similarity, Sen, K. (Ed.), Springer-Verlag, Heidelberg. 

Mezey, P.G. Density Domain Bonding Topology and Molecular Similarity Measures. 173, 63-83 (1995). 

Figure 1. Illustration of lone electron pair preferences in alcohol dimers, cooperative and anticooperative binding sites for a third monomer, ring strain and steric repulsion in alcohol trimers, alternation of residues in alcohol tetramers, and chain, branch, and cyclic hydrogen bond topologies in larger clusters.

Once the alcohol or at least the cluster contains a soft ionization or fluorescence chromophore, a wide range of experimental tools opens up. Experimental methods for hydrogen-bonded aromatic clusters have been reviewed before [3, 19, 175]. Fluorescence can sometimes behave erratically with cluster size [176], and short lifetimes may require ultrafast detection techniques [177]. However, the techniques are very powerful and versatile in the study of alcohol clusters. Aromatic homologs of ethanol and propanol have been studied in this way [35, 120, 121, 178, 179]. By comparison to the corresponding nonaromatic systems [69], the O—H - n interaction can be unraveled and contrasted to that of O—H F contacts [30]. Attachment of nonfunctional aromatic molecules to nonaromatic alcohols and their clusters can induce characteristic switches in hydrogen bond topology [180], like aromatic side chains [36]. Nevertheless, it is a powerful tool for the size-selected study of alcohol clusters. 

While the O—H stretching mode is a sensitive indicator of weak hydrogen bonds to fluorine and the hydrogen bond topology, there are other dynamical... 

T. B. Adler, N. Borho, M. Reiher, and M. A. Suhm, Chirality induced switch in hydrogen bond topology Tetrameric methyl lactate clusters in the gas phase. Angew. Chem. Int. Ed. 45, 3440 3445 (2006). 

Their chemical bonding topologies can be analyzed as follows ... 

Some examples of bare ionic post-transition metal clusters are depicted in Fig. 3. Their chemical bonding topologies can be analyzed as follows ... 

The values of Cy, of course, depend on which equipotential surface is used to represent the ion. Since these surfaces can be arbitrarily chosen, it might be supposed that all the values of Cy can also be arbitrarily chosen. However, the number of ions is always less than the number of bonds. If there are ions in the array, it is only possible to assign arbitrary values of Cy to - 1 bonds, those in the spanning tree described in Section 2.5 below. For the remaining bonds, those that close the loops in the network, a knowledge of the bond topology alone is insufficient to determine Cy. To find these values of Cy, the geometry of the array, i.e. the positions of the ions, must also be known. 

Hawthorne, F. C. (1992b). Bond topology, bond valence and structural stability. In G. D. Price and N. L. Ross (eds). The Stability of Minerals. London Chapman and Hall, pp. 25-87. 

Log P and MR are considered thermodynamic descriptors, pR a combined thermodynamic and electronic index, and a an electronic property index, E is designed to account for steric effects. Corrections for non-additivity, based upon the chemical bonding topology, have been suggested and used. These include proximity, bond type, ring, and group shape correction features. (8-10)... 

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