Complex, crystalline molecular

Ballesteros, B., Coco, S. and Espinet, P. (2004) Mesomorphic Mixtures of Metal Isocyanide Complexes, Induding Smectic C Mesophases at room temperature and Liquid Crystalline Molecular Alloys . Chemistry of Materials, 16, 2062-2067. 

Herbstein FH (2005) Crystalline molecular complexes and compounds structures and principles, vol 2. Donor-acceptor molecular compounds (essentially localized interactions), Chap 11. Oxford University Press, London... 

As mentioned before, we shall use small molecules to introduce the fundamentals for more complex molecules, the real core of this book, which will be listed in the next section. Such molecules form solids with remarkable properties (metallicity, superconductivity, ferromagnetism, etc.), some of them at ambient conditions or at much lower hydrostatic pressures than those found for H2 and N2, and some technological applications have been already developed, deserving the name of functional materials. Most of the molecules studied in this book are planar, or nearly planar, which means that the synthesized materials reveal a strong 2D structural character, although the physical properties can be strongly ID, and because of this 2D distribution we shall study surfaces and interfaces in detail. In particular, interfaces play a crucial role in the intrinsic properties of crystalline molecular organic materials and Chapter 4 is devoted to them. 

At low temperatures in inert solvents (such as methylene dichloride) a controlled polymerization can be effected using various acids and alkylating agents. These initiators include boron trifluoride etherate, triethylaluminum, trityl hexachloroantimonate, triethylam-monium hexachloroantimonate, diethyloxonium hexafluoroantimonate, p-toluenesulfonic acid and diethylzinc or cadmium-1,2-dioI complexes. Crystalline, high molecular weight... 

On the other hand, nitrosyl bromide is ineffective. This may be attributed to the fact that the reagent is extensively dissociated to afford nitric oxide and molecular bromine. Furthermore, in the case of some amides, reaction with nitrosyl bromide results in the formation of complex crystalline compounds containing reactive bromine. 

Crystalline molecular complexes and compounds structure and principles... 

The compound on the right (hexahelicene) is also of interest because it was resolved by forming a crystalline molecular complex with a polynitro compound/ ... 

Accurate determination of the structures of molecular inclusion complexes and molecular assemblies has gained in importance in supramolecular chemistry and recently in crystal engineering. Detailed information about the nature of these weak intermolecular interactions is crucial in order to understand and further develop supramolecular systems and understand crystal growth and the properties of crystalline materials. Particularly accurate structural information can be gained in the solid state by single crystal X-ray crystallography. 

When the intermolecular forces are relatively strong and directional, crystalline molecular compounds (crystalline molecular complexes) are formed. They have fixed stoichiometries and ordered structures. These two-component molecular crystals are also called cocrystals or maybe adduct crystals. Hydrogen-bonded cocrystals, donor-acceptor crystals (charge transfer crystals), and inclusion crystals (host-guest crystals) are examples of crystalline molecular complexes. Crystalline organic salt is a special case of hydrogen-bonded cocrystal or donor-acceptor crystal, i.e., proton (or electron) transfer from the acid (or donor) to base (or acceptor) occurred. 

Figure 1 Three typical temperature versus composition diagrams for a binary system (A and B) (a) diagram with a eutectic point E (b) diagram for the case of unlimited solubility (c) diagram showing formation of a molecular complex M. Diagrams a-c represent the simplest case, respectively, where a simple mixture of component crystals, a solid solution (mixed crystal), or a crystalline molecular complex is brought about.

When molecules of the two components have unlimited solubility both in the liquid and in the solid state, diagram b is obtained. The solid phase corresponds to a solid solution or a mixed crystal. Diagram c represents a case whereby a crystalline molecular complex M of the composition A ,B (m = n = 1) is formed and, besides, the complex M does not form solid solutions with its components A and B. This diagram is the sum of two diagrams similar to example a. 

We have found that indole and trans-cinnamic acid form a weak crystalline molecular complex [38]. This finding triggered extensive investigations of photore-active hydrogen-bonded cocrystals by Ryukoku workers [39-41]. 

Appendix 2. Numerous Examples of Crystalline Molecular Complexes. 

Halogen bonding also manifests itself in the relative orientations of halogen derivatives in the crystalline state [149]. Indeed, the modes of interaction in many nonhydrogen-bonded noncovalent systems, ranging from gas phase complexes to molecular crystals, can be satisfactorily rationalized in terms of molecular surface electrostatic potentials [44,55,150]. In several instances, we have used this approach to explain anomalously high measured solid densities [151,152]. 

O Day PA, Newville M, Neuhoff PS, Sahai N, Carroll SA (2000b) X-ray absorption spectroscopy of strontium(II) coordination I. Static and thermal disorder in crystalline, hydrated, and precipitated solids and in aqueous solution. J Colloid Interface Sci 222 184-197 O Day PA, Parks GA, Brown GE Jr (1994c) Molecular structure and binding sites of cobalt (II) surface complexes onkaolinite from X-ray absorption spectroscopy. Clays Clay Minerals 42 337-355 O Day PA, Rehr JJ, Zabinsky SI, Brown GE Jr (1994a) Extended X-ray Absorption Fine Structure (EXAFS) analysis of disorder and multiple-scattering in complex crystalline solids. J Am Chem Soc 116 2938-2949... 

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