Solid state molecules molecular crystals

Supramolecular chemistry, or chemistry beyond the molecule, has provided a wide canvas for a variety of studies of molecular materials in the solid state. The most orderly manifestations of the solid state are single crystals, and the earlier volume in this series with the present Editor, The Crystal as a Supramolecular Entity, sought to establish that the crystal is the perfect example of a supramolecular assembly, justifying as it were the earlier statements of Dunitz and Lehn in this regard. 

In the solid state, molecules line up in a pattern forming a crystal lattice similar to that of an ionic solid, but with less attraction between particles. The structure of the crystal lattice depends on the shape of the molecule and the type of intermolecular force. Most information about molecules, including properties, molecular shape, bond length, and bond angle, has been determined by studying molecular solids. 

Second, being quasibound Inside a potential barrier on the perimeter of the molecule, such resonances are localized, have enhanced electron density In the molecular core, and are uncoupled from the external environment of the molecule. This localization often produces Intense, easily studied spectral features, while suppressing non-resonant and/or Rydberg structure and, as discussed more fully below, has a marked Influence on vibrational motion. In addition, localization causes much of the conceptual framework developed for shape resonances In free molecules to apply equally well to photolonlzatlon and electron scattering and to other states of matter such as adsorbed molecules, molecular crystals, and Ionic solids. 

Crystal deconstruction is the process that leads backwards. in a reverse "aufbau process, from the structure of a molecular crystal to the component molecules or ions. Crystal deconstruction allows one to focus on the interactions that are more relevant for crystal structure cohesion. The objective of the deconstruction process is also that of learning about the factors responsible for molecular/ionic recognition and self-assembly in the solid state. Insights into crystal polymorphism can be gained by comparing the different distributions of intermolecular interactions associated with the existence of different crystal forms of the same molecular species. 

Alternate LB layers. The LB technique provides the possibility for alternate layers of different sets of molecules, which are forced to come in contact in the polar plane. The only requirement is that the attraction between the polar head is greater than the attraction with water. This powerful procedure allows a great many combinations for solid-state architecture (non centro-symmetric crystals, hetero duners, solid-state synthesis, molecular recognition). 

Molecular recognition-directed processes also provide a powerful entry into supramolecular solid state chemistry and crystal engineering. The ability to control the way in which molecules associate may allow the designed generation of supramolecular architectures in the solid state. Modification of surfaces with recognition units leads to extended exo-receptors [1,3] that could display selective... 

Synergy in molecular recognition and self-assembly occurs in various phases in both solutions and also in solid states and liquid crystals. On-surface self-assembly possesses a special advantage in that molecules are visualized by scanning tunneling microscopy (STM). This allows us to gain detailed insight into how molecules act cooperatively with each other. 

Excimers (considered also as electronically excited complexes) are formed in solutions, liquids or in the solid state if the crystal structures or chain conformations allow a close overlap of the molecular planes of paired molecules. Excitation of one member of this paired molecule by direct absorption of light or by energy transfer from a nearby excited molecule may lead to formation of an excimer. 

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