Electron density shape analysis of a family of through-space and through-bond interactions

Abstract

A family of styrene derivatives has been used to study the effects of through-space and through-bond interactions on the local and global shapes of electron densities of complete molecules and a set of substituents on their central rings. Shape analysis methods which have been used extensively in the past for the study of molecular property-molecular shape correlations have shown that in these molecules a complementary role is played by the through-space and through-bond interactions. For each specific example, the dominance of either one of the two interactions can be identified and interpreted in terms of local shapes and the typical reactivities of the various substituents. Three levels of quantum chemical computational methods have been applied for these structures, including the B3LYP/cc-pVTZ level of density functional methodology, and the essential conclusions are the same for all three levels. The general approach is suggested as a tool for the identification of specific interaction types which are able to modify molecular electron densities. By separately influencing the through-space and through-bond components using polar groups and groups capable of conjugation, some fine-tuning of the overall effects becomes possible. The method described may contribute to an improved understanding and control of molecular properties involving complex interactions with a possible role in the emerging field of molecular design.

An alternative to the “Star Path” enhancement of the ADMA linear scaling method for protein modeling

“…As doubling or tripling of both the central regions and the “surroundings‐reproducing” regions of parent molecules are the simplest to interrelate, and therefore, the simplest to recognize potential computational benefits if their sizes show simple proportionalities by small integer ratios, we shall focus on doubling, tripling, or quadrupling these sizes. If several options for fragmentation methods are available, this can be advantageous also in computations of fragment interactions in smaller molecules as well …”

“…This approach is based on a curvature analysis of the chemically relevant range of all isodensity contour surfaces of the electron density fragment, leading to a Group‐Theoretical description based on Homology Groups, and the ranks of these groups, called Betti numbers provide a detailed “shape‐code,” where such shape codes can be compared numerically, providing detailed, actual shape similarity measures. The methodology has been described on several occasions (see, e.g., and references therein, see also the more recent applications …”

“…The electron density shape similarities have been evaluated using the standard Shape Group methodology, as described most recently in references …”

UV Photoelectron Spectroscopy and Outer Valence Electronic Structure of Dihalobenzenes

“…We used accurate vertical ionization energies (which are good approximations of orbital energies) obtained from UV photoelectron spectroscopy (UPS) as the quantitative probe of TB and TS effects. Antal et al 1 selected substituted styrene derivatives as their test case. However, we use smaller dihalobenzenes, because they exhibit well resolved spectral bands thus allowing accurate ionization energies to be measured; this would not have been possible with larger styrene derivatives where the bands can be expected to overlap in the spectra.…”

“…1 The authors used theoretical method of shape analysis to provide quantitative measure of through-bond (TB) and through-space (TS) effects. Because of our long standing interest in the analysis and systematization of halogen substituent interactions in halobenzenes, we provide in this note some experimental results which can be useful for assessing the validity of theoretical concepts attached to TB and TS effects.…”