Solid state packing

A further advantage of PTHP 11 is that distereomeric forms can be generated which are exclusively composed of c/.v- or mu/.v-configurcd monomeric THP building blocks. The stereochemistry of the substituents in 4- and 9-position (m, trans) strongly influences the solid state packing behavior of 11. 

The Rh-Rh distance is 3.12 A, long compared with Rh-Rh single bonds (2.624A in Rh2(MeCN) J([, 2.73 A in Rh4(CO)12) there is a weaker (3.31 A) intermolecular attraction. Dipole moment and IR studies indicate that the structure is retained in solution and is, therefore, a consequence of electronic rather than solid-state packing effects. Furthermore, it is found for some other (but not all) [RhCl(alkene)2]2 and [RhCl(CO)(PR3)]2 systems. SCF MO calculations indicate that bending favours a Rh-Cl bonding interaction which also includes a contribution from Rh—Rh bonding [56b]. 

Figure 8.26 Schematic formula (a) molecular single crystal X-ray diffraction structure (b), and solid state packing (c) ofthe cationic gold complex [Au bimy(Ci6H33) 2]Br H20. (Reproduced from Ref [52] by permission.)...

Discussions here have focused on the more well-characterized salts based on the [CiCilm]+ cation, but this is a somewhat model system, and may accentuate the interactions observed in many of these examples. Where longer alkyl chains are present on the cation liquid and solid-state packing are disrupted and can lead to the formation of ionic/nonionic microdomains in the liquid and which may have a considerable influence on the dissolution of solutes [49]. 

A view depicting the solid-state packing of 10 is shown in Figure 16. The bricks of 10a and 10b have assembled such that they form identical... ABA... stacking patterns, the corners of the bricks lying above and below the cavities of another. As a result, the guests are completely enclosed such that there are... 

Furthermore, secondary bond distances vary widely, even among chemically equivalent bonds in the same complex (e.g., from 264.0pm to 292.6pm for Ag-Cl contacts in Ag[CBiiH6Cl6] " ). One wonders whether these differences signify any difference in secondary bond strength or bond order, or whether secondary bonding involves such a shallow potential well that the differences merely represent variations in what is needed to achieve optimal solid-state packing. 

An intriguing property of PFs is their ability to form liquid crystalline phases [38,39]. Besides the different mesophases which are classified as nematic, poly(9,9-dioctyl)fluorene (PFO) shows several solid-state packing properties and polymorphs. The pioneering work of Grell et al. showed how solvent swelling and thermal cycling could be used to control the solid-state packing in PFO thin films [38,40]. In addition, the different phases show remarkably diverse photophysical properties, which have tremendous... 

The first report of a topochemical 1,6-polymerization of a conjugated triene was recently described by Lauher and co-workers [39]. In particular, the double ester of l,8-dihydroxy-2,4,6-octatriene and nicotinic acid (Scheme 2.3.5) was found to adopt a solid-state packing arrangement conducive for the 1,6-polymerization. Specifically, the molecules were oriented at a repeat distance of 7.2 A (Fig. 2.3.3(a)). Although the separation between terminal carbon atoms of adjacent triene moieties was somewhat large (4.09 A), the solid underwent a SCSC topochemical... 

Figure 20. Solid-state packing of nanotube 45 n — 1) (X-ray structure).

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