Crystallizing solvent, nature

Giitlich et al. [4, 6] have studied SCO in solid [Fe(2-pic)3]Cl2-EtOH (2-pic = 2-picolylamine), particularly the influence of dilution with Zn and Co, the nature of noncoordinated anions and crystal solvent, the HID and isotope effect,... 

Most, if not all of the larger size natural cyclic peptides contain one or more N-alkylated amino acid residue. Their ring conformation depends on the substitution patterns as well as on environmental conditions (crystal, solvent). As a result of the large number of energetically similar and thus allowed conformational states, their 3D structure can not be predicted with great certainty. 

The variety of materials which can be incorporated into polyelectrolyte multilayers makes them attractive to use as biosensors [431], Polyelectrolyte multilayers can also be formed on curved surfaces of small particles [432], After adsorption, the core particle can be chemically dissolved and a hollow polyelectrolyte capsule remains. These capsules are selectively permeable for small molecules like water or certain dyes. The permeability can be tuned externally by varying the ion strength, pH, temperature and solvent nature [433 135], Therefore, it has been suggested to use them as selective membranes for separation, as well as a possible drug delivery system. The adjustment of their size and permeability allows us to exploit them as micro- or nanocontainers for chemical synthesis and crystallization. 

When a molecule is partly oriented by dissolution in a liquid crystal solvent it is necessary to consider direct dipolar splittings, nuclear screening anisotropies, and possibly also very large quadrupolar splittings, in order to account for the spectrum. The ways in which this can affect multiple resonance experiments have been considered already. (33, 35-37, 46) In this section we discuss some applications. Naturally, proton decoupling is often used to simplify spectra of oriented molecules, although it is desirable to avoid complete decoupling of the solvent protons. 

Nature of crystallizing solvent More affinity for crystallizing solute... 

A high-resolution, phase-sensitive, natural abundance F2-coupled HSQC (F2HSQC) NMR experiment has been developed by Marathias et al to measure simultaneously both "Z>hh and Dhc residual couplings (RDCs) of small molecules present in a chiral polypeptide Uquid crystal solvent system composed of poly-y-benzyl-L-glutamate (PBLG) in CDCI3. 

Although water and/or solvent(s) of crystallization are the most common "extraneous lattice components" (hydrates/solvates), many examples demonstrate that stable 3d arrangements/crystal structures can be assembled with the aid of a surprisingly wide variety of "extraneous chemical compounds" (co-crystals). If Nature co-operates in our designs, some choices of "extraneous components" may lead to improved physical and/or biological properties of novel co-crystals. 

The different modifications can be obtained by changing the crystallization conditions, nature of solvent, solution concentration, thermal history of the solution, and cooling rate, see Tables 6 and 7 [100-102]. 

The twist induced by different molecular species can be qualitatively related to the molecular structure of the chiral species [40]. The twist induced in a nonchiral liquid crystal solvent by a chiral dopant also depends on the nature of the solvent, and it has been proposed that chiral dopants can preferentially promote chiral conformations of the solvent molecules [41]. This effect has also been observed in isotropic solutions, where an enhanced optical rotation in solutions of a chiral biaryl in a cyanobiph-enyl solvent was attributed [42] to an induction of chirality via preferential interactions... 

Molecules dissolved in liquid crystal solvents become partially oriented, the degree of orientation being dependent on the nature and concentration of the solute. 

The aggregation of surfactants into clusters or micelles in dilute solutions, as we will see, is a direct consequence of the thermodynamic requirements of the particular surfactant-solvent system under consideration. It has been suggested that phases occurring between the simplest micelles and true crystals are natural consequences of the removal of water from the micellar system, but do not constitute thermodynamically distinct states. In other words, the factors determining the structures of the mesophases are identical to those that control the formation of micelles in the first place. The same would be true of aggregates other than micelles, which do not fall under the classification of mesophases. 

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