Multi-component molecular crystals

The concept of the multi-component molecular solid covers co-crystals, mixed crystals, salts, clathrates, and complexes. As Yan and Evans have indicated,multi-component systems of luminescent dyes with a variety of co-assembled units offer a more flexible method for tuning the packing-directed luminescent properties of the dye than the formation of polymorphs of the pure material. An example has already been given above (16). ° Another example is the organic salts of anthracene-2,6-disulfonic acid (20) with amines (Scheme 6). ... 

Co-crystal A stoichiometric, crystalline molecular complex of two or more chemically different compounds. Sometimes called a multi-component molecular complex. 

FE data have been collected from the fracture of a wide variety of single and multi-component solids, ranging from single crystals of molecular solids to fiber-reinforced composites, and also from the peeling of adhesives 0-16 ). In this paper, we will restrict our attention to FE arising from the failure of polymer composites (fibrous and particulate), and the individual components thereof (fibers and matrix resins). 

This chapter surveys unimolecular and bimolecular photochemical reactions in mixed molecular crystals and solid mixtures. Various photoreactions occurring in mixed crystals (solid solution), hydrogen-bonded cocrystals, donor-acceptor crystals, crystalline organic salts, and solid mixtures are described. In contrast to one-component crystals [2], the organic photochemistry of such multi-... 

The aluminophosphate molecular sieves (AiP04 s) consist of aluminum and phosphorus linked by oxide ions. In the larger family of aluminophosphate based molecular sieves with three or more framework cations an additional 13 elements have been incorporated with a variety of crystal structures. The whole aluminophosphate based molecular sieve family comprises more than two dozen crystal structures and about two hundred compositions. While AIPO4 molecular sieves with only two framework elements are catalytically inactive, most of the three or multi-component aluminophosphate based molecular sieves possess cation exchange capacity, and in the protic form they display carboniogenic catalytic activity. 

Not just multi-component crystal structures but even simple molecular crystals can be quite difficult to classify using a simple predictive ranking of hydrogen bonds. Phenyl... 

The problems of nonequilibrium crystallization and melting discussed in Chap. 6 and Sect. 7.1 for single-component systems, are even more pronounced for multi-component systems. The additional problem of separating the components by diffusion into phases of different concentration complicates the description of multi-component systems even further. Usually equilibrium concentrations cannot be achieved at the moment of crystallization or melting, i.e., the processes of component diffusion and crystallization/melting are not molecularly coupled. One must thus always consider two deviations from equilibrium. One is the formation of non-... 

Polymer phase separation and crystallization, as introduced separately in the previous two chapters, have different molecular driving forces that can be simultaneously expressed by the use of the lattice model. Adjusting the corresponding driving forces, the mean-field theory can predict the phase diagrams, and at the meanwhile molecular simulations can demonstrate the complex phase transition behaviors of polymers in the multi-component miscible systems. 

The inorganic chemistry of a multi-component heterogeneous catalyst is often very complex, as it is quite difficult to obtain structural information at the molecular level to help establish the fundamental processes. As an example, we discuss the chemistry of the complex mixed metal oxide catalyst Mo7,5Vi,5NbTe029 shown in Fig. 2.25, which is known to catalyze the ammoxidation of propane to acrylonitrile. The active centers in this system are multifunctional metal oxide assemblies that are spatially isolated from one another owing to their unique crystal structures. 

Salts, and more recently co-crystals, have attracted much interest in the pharmaceutical industry for their promise in tailoring the physical properties of an active pharmaceutical ingredient (API) to meet the needs of the drug product and ultimately the patient.Salt forms, produced by add (A)-base (B) reactions in the solid state, are multi-component solids comprising minimally an A B pair they may be crystalline or amorphous. The term co-crystal, on the other hand, refers specifically to crystalline molecular complexes, which may include an A B pair among the different components and by definition necessarily include solvates (hydrates), inclusion compounds, clathrates and solid solutions. 

---