Molecular complex , definition

Homogeneous catalysts are very often known as examples of single-site catalysts characterized by complete structural definition and (presumably) complete knowledge of the chemical processes occurring at their catalytic centers. It is a matter of fact that the homogeneous catalysts are molecular complexes constituted by an active core containing a single active atom (of-... 

In almost all examples of molecular complexes discussed here Aq(z) becomes zero somewhere in between both subsystems A and B (see Figs. 12-16, 18, 23). In our first definition we draw a borderline at this value of z ... 

A new definition of molecular similarity is presented, based upon the similarity of the corresponding molecular graphs. First, all of the subgraphs of the molecular graph are listed, and then various similarity indices are derived from the numbers of subgraphs. One of these compares favorably with the standard distance measures of sequence comparison. Measurement of similarity provides a new way to measure molecular complexity, as long as the most (or least) complex member of a set of molecules can be identified. 

The term exciplex (excited complex) is used to describe an electronically excited molecular complex of definite stoichiometry. Complexes which fall into this broad classification include ... 

General Theory. In addition to the work already quoted, a few papers considering various aspects of the general theory of polarizabilities are also included. We mention the efforts to consider the effects of the polarizability of relatively crude models (such as metallic spheres) [101, 103]. The tensor representations of molecular polarizabilities have been carefully discussed [84, 141, 362]. More general procedures applicable to a variety of systems (including big molecules and molecular complexes) that are often based on classical electrostatics have been proposed [4, 21, 118, 119, 127, 135, 136]. Various books and articles are concerned with the definition of the terms in common use [12, 13, 20, 91, 109]. Other articles deal with relevant general properties of matter [22, 113] and molecules in electric and magnetic fields [31,239], triplet polarizabilities [10,61, 102,126,208], and the calculations of polarizabilities of molecules in the liquid. 

Crystal engineering is a highly interdisciplinary area, which to some extent explains why unambiguous definitions and systematic nomenclatures have yet to be fully developed. The term co-crystal is not well-defined, and the existing literature contains terms such as molecular complexes, co-crystals, molecular adducts,... 

Physically, it is most reasonable to assume that a wide spectrum of aggregates, ranging from 1 1 to something best described as a solvent cage, may occur. Thus, for example, chloroform and toluene definitely form a 1 1 molecular complex (cryoscopic evidence ) and, by inference, probably associate in a 1 1 ratio in solution. However, at the other end of the spectrum, some systems are perhaps best described without reference to specific stoicheiometries and geometries in such instances, pictorial representations of the collision complexes do not have any physical significance. 

Fig. 5. Molecular complexes, (a) Building molecular complexes by dragging and dropping their molecular components into the complex definition field, (b) After double-clicking the lines linking molecular binding sites the sites will be associated.

As mentioned in Subheading 3.1.5 even fiw /c-molecular complexes intended for use in cellular mechanisms or for the definition of specific enzymatic transformations or for manipulations performed on running simulations have to be defined as complexes since simmune s simulation interface does not offer access to molecules, only complexes. If cAMP is not listed in the molecule type list in the molecule concentration fields window you have probably not defined it as a complex. 

No conclusion can adequately summarize the developments in the topic of this article. Host-guest chemistry is still in its infancy as a typical multidisciplinary subject. The progress in all basic disciplines will immediately provoke progress in the level of our knowledge on molecular complex formation by calixarenes. The synthesis of many new ligands and their thorough study will definitely be required to better understand the multifaceted problem of molecular recognition and complex formation. 

The term species may mean a discrete molecule, a simple or complex ion or even a solid exhibiting non-molecularity in one or more dimensions (graphite as an example). Free atoms seldom act as Lewis acids and bases. They usually have one or more unpaired electrons and flieir reactions are more accurately classified as free radical. The donor orbital is usually die highest occupied molecular orbital HOMO, and the acceptor orbital is usually the lowest unoccupied molecular orbital or LUMO. The molecular orbital definitions have a number of important consequences ... 

Although the proposed models have been successful in describing several weak to moderate types of molecular interactions, it is important to note the definition of ad hoc parameter K. The computation of this parameter is rather difficult hence, further study should be made on the evaluation of the parameter K. Another critical aspect is that because the descriptors of isolated reactants are anployed in the energy expression, these models are expected to be applicable only for the cases where the influence of one monomer reactant on another molecule is comparatively less. Having said the limitations of the proposed models, these models, nevertheless, can rationalize the relative influence of the hardness/softness parameters in determining the nature of different types of interactions and stabilization of the molecular complexes, thus transforming the once thought qualitative HSAB principle into a quantitative one. 

S.H. Bertz and W.F. Wright, The graph theory approach to synthetic analysis Definition and application of molecular complexity and synthetic complexity. Graph Theory Notes NY 35 (1998) 32-48. 

---