Peripheral hydrogen-bonding

The use of coordination compounds with peripheral hydrogen-bonding substituents in the formation of infinite one-, two-, and three-dimensional frameworks, which can be used for host/guest chemistry, has recently been reviewed by Beatty. Brammer and Rivas, on the other hand, have reviewed the hydrogen bonding in substituted ammonium salts of the tetracarbonylcobaltate(i) anion. The reader is addressed to these two papers for a detailed analysis. 

Porphyrin Gelators with Peripheral Hydrogen-Bonding Functionalities. . 124... 

Karikari, A.S., Edwards, W.F., Mecham, J.B., and Long, TE. (2005) Influence of peripheral hydrogen bonding on the mechanical properties of photo-cross-Unked star-shaped poly(o, L-lactide) networks. Biomacromolecules, 6,2866-2874. 

Carbamazepine (CBZ, 87) (Scheme 3.16), is an important antiepileptic agent in use for more than 30 years but suffers from low water solubility and oral bioavailability. Hickey and coworkers [129] prepared a cocrystal with saccharin (88) employing the peripheral hydrogen bonding capabilities of CBZ dimer. The cocrystal was found to possess favorable dissolution properties, suspension stability and pharmacokinetics using dog models. Similarly, Zaworotko, Shytle and CO workers [130] used cocrystallization to improve solubility and oral bioavailability of quercetin. 

However, it is reasonable to identify the pair of water molecules in the channel as a supramolecular water dimer because this pair is not at all involved in covalent interaction and is solely hydrogen bonded to its periphery. At this point, it is worth mentioning that, even though we have described this pair of water molecules as a water dimer, contributions from the peripheral hydrogenbonding sites (POM cluster anion and sodium-coordinated waters) are unavoidably significant for the existence of this smallest water cluster. Thus the formation of supramolecular (H20)2 in the channel appears to be facilitated by the peripheral hydrogen-bonding interactions POM cluster anions. 

FIGURE 41. (a) Hydrogen-bonded water trimer (shown in violet), (b) Hydrogen bonding situation describing the water trimer (shown in violet) and its peripheral hydrogen bonding sites. Color code. Mo, yellow O, red Cu, blue H, white. (Reprinted with permission from ref. 52.)... 

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