Solvent of crystallization

Crystal stmcture analyses of cyanine and related dyes are reviewed in Ref. 32. Most typical sensitizers are nearly planar, with angles of less than 15° between planes defined by heterocycHc rings. Distinct solvent of crystallization is present in most of the cationic dyes. X-ray crystal analyses also provide intermolecular data. Because of photographic use of cyanine and carbocyanine dyes, the cation-cation arrangements of most interest have been those for l,l -dieth5l-2,2 -quinocyanine chloride [2402-42-8] 5,5, 6,6 -tetrachloro-l,l, 3,3 -tetraethylbenzimidazolocarbocyanineiodide [3520-43-2] and 5,5 -dichloro-3,3, 9-triethylthiacarbocyanine bromide [18426-56-7] (32) (see Fig. 8). 

To a solution of 32 g of benzyl-t-butylamine in 300 ml of absolute ethanol at reflux temperature was added 32 g of 3,5-dibenzyloxy-C0bromoacetophenone in 10 ml of dry benzene. The mixture was refluxed for 20 hours and then evaporated. When absolute ether was added to the residue, benzyl-t-butylamine hydrobromide was precipitated. The precipitated compound was filtered off and to the filtrate was added an excess of 2N sulfuric acid. This caused precipitation of the hydrogen sulfate of 3.5-dibenzyloxy-60-(benzyI-t-butylamino)-acetophenone which was recrystallized from acetone/ether. If the product is crystallized from different organic solvents, the melting point will vary with the type and amou nt of solvent of crystallization, but the product can be used directly for hydrogenation. 

Cu-Cu 3.153 A).279 They also structurally characterized a complex similar to complex (310) (r = 0.17), with a water molecule as solvent of crystallization and without the N02 substituent in the ligand.279 Neves et al.2S0 reported an interesting structure (complex (318)) in which the two phenol oxygen atoms remain protonated and coordinate to copper in an axial fashion. 

An enormous variety of solvates associated with many different kinds of compounds is reported in the literature. In most cases this aspect of the structure deserved little attention as it had no effect on other properties of the compound under investigation. Suitable examples include a dihydrate of a diphosphabieyclo[3.3.1]nonane derivative 29), benzene and chloroform solvates of crown ether complexes with alkyl-ammonium ions 30 54>, and acetonitrile (Fig. 4) and toluene (Fig. 5) solvates of organo-metallic derivatives of cyclotetraphosphazene 31. In most of these structures the solvent entities are rather loosely held in the lattice (as is reflected in relatively high thermal parameters of the corresponding atoms), and are classified as solvent of crystallization or a space filler 31a). However, if the geometric definition set at the outset is used to describe clathrates as crystalline solids in which guest molecules... 

With the long alkyl chain substitutions on the A-heterocyclic carbenes, lamella-structured silver(i) carbene complexes 27a and 27b (Figure 14) were isolated.74 It is interesting to note that the synthetic procedures for the two complexes are the same except for the use of different solvents of crystallization. The dinuclear 27a was obtained from recrystallization in dichloromethane- -hexane while the tetranuclear 27b was obtained from acetone. The structure of 27a could be interpreted as the dimeric form of [Ag(carbene)Br] bridged by intermolecular Ag-Br interactions. The Ag-G bond has a distance of 2.094(5) A. The tetranuclear 27b, on the other hand, could be regarded as two monocationic bis(carbene)silver(i) bridged by an [Ag2Br4]2 anion, with the presence of short Ag(cationic)-Ag(anionic) contact (3.0038(18) A) and comparable Ag-G bond distances (2.0945(5), 2.138(13) A). A related... 

Triphenylcarbinol separates from carbon tetrachloride with solvent of crystallization. The solvent is readily lost on exposure of the crystals to air. The weight mentioned is that of the solvent-free product. 

II, and III), two were monohydrates (termed a-monohydrate and /3-monohydrate) and one was a ferf-butylamine disolvate. The differences in the powder patterns of the phases were readily evident (Table 1). This study demonstrates the unique ability of x-ray diffractometry for the identification of (1) anhydrous compound existing in both crystalline and amorphous states, (2) different polymorphic forms of the anhydrate, (3) the existence of solvates where the solvent of crystallization is water (hydrate) or an organic solvent (in this case, /m-butylamine), and (4) polymorphism in the hydrate. 

Divalent or higher-valent cations and, in particular, transition metal cations, are likely to be covalently solvated by solvents that are strong electron pair donors (have large solvatochromic P values). This solvation often persists in crystals, so that the salt that is in equilibrium with the saturated solution in such solvents may not be the anhydrous salt (nor the salt hydrate). Equation (2.56) omits any consideration of the solvent of crystallization and pertains to the solventless (anhydrous) salt. For a salt hydrated by n water molecules in the crystal, the activity of water raised to the nth power must multiply the right-hand side of Eq. (2.56) for it to remain valid. A similar consideration applies for salts crystallizing with other kinds of solvent molecules, the activity of the solvent in the saturated solution replacing that of water. Such situations must be... 

DMEDO-TSeF afforded eight superconductors. Six of them are k-(DMEDO-TSeF)[Au(CN)2](solvent) and their T s (1.7-5.3 K) are tuned by the use of cyclic ethers as solvent of crystallization [262]. 

A seemingly minor technical problem, the ability of triphenylmethyl to pick up virtually any solvent as solvent of crystallization, occupied Gomberg for some time and led him into consideration of then fashionable structures involving tetravalent oxygen, which were later abandoned. Another sidetrack, more serious in view of the absence of a useful theory, was caused by experiments based on the known fact that triphenylchloromethane showed salt-like conductivity in solution in liquid SO2 It was thus definitively established that there are carbonium salts in the true sense of the definition applied to salts. When triphenylmethyl was dissolved in liquid SO2, it was found that it too conducted the electric current quite well. " How should one explain this strange phenomenon, a hydrocarbon behaving like an electrolyte ... 

Nearly planar molecules (tetrahydrofuran, occurring as solvent of crystallization, is a notorious example) often lie on a symmetry plane, meaning, in fact, that some of the atoms are actually in the plane while others are disordered on either side, as shown below ... 

In the solid state, long Aib-rich peptides (more than eight residues) form a mixed 3i0/a-helix, depending on the solvent of crystallization. 35 37] The enhanced electrostatic interaction and improved packing in a 310-helix makes it very easy to crystallize. These are but empirical generalizations and it is the balance of these factors, along with the steric requirements of the amino acid side chains, which ultimately determines the type of helix that will be formed. 

In the crystalline complex, solvent molecules can be bonded not only to the cation, but also to the anion and the carbohydrate. A detailed x-ray study has snown that, in sucrose NaBr 2 HjO, each Br ion has bonds to one water molecule, one Na ion, and four carbohydrate hydroxyl groups.00 The ability of a complex to possess solvent of crystallization, even when the free individual components themselves are incapable of doing so under the same conditions of temperature, is exemplified by the formation of sucrose Nad 2 H2O at room temperature. Sucrose and sodium chloride crystallize from their aqueous solutions in the nonhydrated form. 

The fact that only naked molecules are refined is based on the problem that for crystal lattices at least 27 unit cells would have to be included (with at least one unit per cell, including counter ions and solvents of crystallization), and in solution at least 200 molecules of water must be refined in the solvent sheath interacting with the compound to be modeled. Since CPU time f(m2), where m is the number of nuclei, the time required for a single optimization cycle increases dramatically under these conditions. Even more importantly, the initial configuration of the molecule and its environment is not easy to predict since the intermolecular contacts (crystal lattice, ion-pairing and solvation) of a compound to be modeled are not known beforehand. Thus, inclusion of environmental effects in modeling studies has necessitated the use of some severe approximations176-781. 

In terms of the refinement illustrated here, the function Y is the function Fix], The first point, Xj, is represented by all variable bond lengths, bond angles, conformation angles, chain position parameters, coordinates of the solvent of crystallization, etc., of the initial model. All other points X2,. .., Xj, represent trial values for the same n variables within the desired interval limits and subject to any other constraints, such as coupling of variables or hydrogen bond formation. Clearly, the number and type of variables, and their limits and constraints are easily changed in this procedure, as is the form of the function. The search procedure is also relatively rapid and does not suffer from a slowdown in the vicinity of the minimum, as may occur in steep-est-descent methods. 

It showed no weight loss up to 200°C, indicating non-volatility and absence of solvent of crystallization. 

Solvent of crystallization is not reported in the formula b Average distance or bond range... 

In a later example [135], it was shown that photodimerization of 3,4-dichlorocinnamic acid (52) proceeds in high yields in various hydrocarbons to give similar mirror-symmetric products with solvent of crystallization. The reaction does not occur in the fluid phase and dimerization of the suspended monomer... 

---