Molecular geometry overview

A short overview of the quantum chemical and statistical physical methods of modelling the solvent effects in condensed disordered media is presented. In particular, the methods for the calculation of the electrostatic, dispersion and cavity formation contributions to the solvation energy of electroneutral solutes are considered. The calculated solvation free energies, proceeding from different geometrical shapes for the solute cavity are compared with the experimental data. The self-consistent reaction field theory has been used for a correct prediction of the tautomeric equilibrium constant of acetylacetone in different dielectric media,. Finally, solvent effects on the molecular geometry and charge distribution in condensed media are discussed. 

In the previous sections single crystal diffraction has been described and an overview of the typical information one may wish to obtain from such an experiment has been presented. This includes chemical composition, atomic positions and molecular geometries, atomic displacements, and, in the context of crystal engineering, the identification of supramolecular synthons, network topologies, cavity sizes, etc. The study of non-covalent interactions is one of the main research... 

Experimental studies of ground state properties of DNA bases have been carried out for many years. This includes studies of their molecular structures. Although one can conclude that the ground state of these important DNA constituents is well characterized, data concerning their excited state properties is scarce. The molecular geometry of such complex systems like DNA bases cannot be determined by experimental methods. It creates a need for theoretical studies that could shed light on the properties of DNA bases in the excited state. In the last chapter of this volume, M.K. Shukla and J. Leszczynski discuss available experimental data of DNA bases, base pairs, and their complexes with water. The discussion is enhanced by an overview of the results of recent... 

The examples in the previous section give a comprehensive overview of application areas where molecular rotors have become important fluorescent reporters. Current work on the further development of molecular rotors can broadly be divided into three areas photophysical description, structural modification, and application development. Although a number of theories exist that describe the interaction between a TICT fluorophore and its environment, the detailed mechanism of interaction that includes effects such as polarity, hydrogen bonding, or size and geometry of a hydrophobic pocket are not fully understood. Molecular simulations have recently added considerable knowledge, particularly with... 

A good, brief overview of the performance of MNDO, AMI and PM3 as of ca. 1999 is given by Levine [87]. Hehre has compiled a very useful book comparing AMI with molecular mechanics (Chapter 3), ab initio (Chapter 5) and DFT (Chapter 7) methods for calculating geometries and other properties [88], and an extensive collection of AMI and PM3 geometries is to be found in Stewart s second PM3 paper [70]. 

Passive micromixers rely on the mass transport phenomena provided by molecular diffusion and chaotic advection. These devices are designed with a channel geometry that increases the surface area between the different fluids and decreases the diffusion path. By contrast, the enhancement of chaotic advection can be realized by modifying the design to allow the manipulation of the laminar flow inside the channels. The modified flow pattern is characterized by a shorter diffusion path that improves the mixing velocity. In this section, an overview of the different types of passive micromixers is provided. Mixed phase passive micromixers can be categorized as ... 

With certain Oomycetes, "sterol-like molecules, eg. tetracyclic and pentacyclic triterpenoids (Fig. 2), may produce the same physiological end response as sterols (2). The growth response to these polycyclic isopentenoids is intimately associated with their 3-dimen-sional geometry, molecular features and subcellular quantity. In order to discuss sterol function for What we assume is an evolutionary determinant of developmental change, a brief overview of sterol occurrence and biosynthesis is given first. 

---