Isostructural species

Seeds of isostructural or quasi-isostructural species that crystalUze well can also been employed to induce crystalUzation of unyielding materials [61]. Heteromolecular seeding [62], whereby near isostructural compounds can be used to template crystallization in less accessible or elusive desired crystal forms, can be apphed. For instance, chiral co-crystals of tryptamine and hy-drocinnamic acid were prepared by crystalUzation in the presence of seeds of different chiral crystals [63]. Of course, imintentional seeding may also alter the crystalUzation process in an undesired manner [64]. 

Periodonium salt (40), like its isoelectronic isostructural species (41) and (42), is stable in solution at room temperature, even in the presence of water. This behavior contrasts markedly with that of the few acyclic periodonium salts which are known. C6FSIF3 SbFs can only be observed at temperature below -10 °C (80ZOR1256). This difference in stability of acyclic and cyclic 10-1-4 species again emphasizes the importance of the five-membered ring. 

In the final section of this chapter, we discuss the vibrational spectra of benzene, its isostructural species CeOg- (rhodizonate dianion), and dibenzene metal complexes. 

Benzene and the rhodizonate dianion (C6C>62-, structure shown above also see Section 20.4.4) are isostructural species. Hence all the symmetry arguments and results given in the previous section for benzene are applicable here. The results for C6C>62- are summarized in Table 7.3.5. 

Fig. 3 Left Results of eompetition experiments. The symbol Xb represents the mole fraetion of Guest B in the liquid mixture and Zb that of Guest B enelathrated in the inclusion compound. The diagonal line represents zero selectivity. Right The five isostructural species isolated. H represents the host molecule (on a center of symmetry), and guest disorder is implied in H.3A.B and H.A.3B. (From Ref. [28]. Reproduced by permission of the Royal Society of Chemistry.)...

Zeolite Stracture Main species FTC Isostructural species... 

---