Formatting, chemical entity

The Swiss authorities made the CTD format mandatory as of 1 July 2002 for new chemical entities (NCEs), as of 1 January 2003 for generics, and as of 1 July 2003 for OTC products and herb-als. The same applies to the other EETA countries (i.e. Iceland, Norway and Liechtenstein). 

The formation of a complex Species by the association of two or more chemical entities (having, in general, electronic closed shells) is one of the most fundamental molecular processes in biology, in chemistry and in physics. Such a super-molecule represents the next higher level of physical complexity after the nucleus, the atom and the molecule. Its formation involves bonding interactions which are much weaker than the usual well defined covalent bonds. 

Precursor A chemical entity that is part of the reaction leading to the formation of another molecule (e.g. a neurotransmitter)... 

The concept of chemical components. Each species can be expressed as the product of a set of chemical components that define the equilibrium problem and a formation constant. Morel (1983) has expressed the definition of the chemical components as a set of chemical entities that permits a complete description of the stoichiometry of the system . For the example of the hydroxy-aluminium species given above Al3+ and H+ are the chemical components. As will be seen in the section on surface complexes the components are not necessarily elements or species. The components concept is important for understanding how to set up chemical equilibrium problems with various computer models. 

Changes in the electronic and molecular structures after CT excitation can also result in chemical bond formation between the excited complex [AB[ and another molecule (Q) of the system, yielding an encounter complex AB-Q. The complex formed by interaction of an excited molecular entity with a ground state partner of the same structure is called an excimer, whereas an electronically excited dimer of definite stoichiometry, formed by interaction of an excited molecular entity with a ground state partner of a different structure, is named an exciplex [29], Both excimers and exciplexes have their own properties and can thus be regarded as new chemical species. Their generation is well documented by the concentration effect on the fluorescence of some solutes or by flash photolysis measurements [11,24],... 

The supramolecular formations and the molecular packing in the crystals show close resemblance, and the nature of the interactions involved is very much the same. There is great emphasis on weak interactions in both. According to Lehn, beyond molecular chemistry based on the covalent bond lies supramolecular chemistry based on molecular interactions—the associations of two or more chemical entities and the intermolecular bond [85], Dunitz expressed eloquently the relevance of supramolecular structures to molecular crystals and molecular packing [86] ... 

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