Cucurbit uril family

Lagona J, Mukhopadhyay P, Chakrabartri S, Isaacs L (2005) The cucurbit[ ]uril family. Angew Chem Int Ed 44 4844-4870... 

The cucurbit [n]uril family (CB[n]) of molecular containers possess remarkable binding affinities and selectivities (Ka values up to 1012M-1, Krei values up to 106) which renders them useful as a component of molecular machines, sensors, and biomimetic systems (123-125). Recently, Wagner and coworkers have reported (126) that CB[10] - with its spacious 870A3 cavity - is capable of acting as a host for free base and metalated tetra (Af-methylpyridinium)porphyrins 19a-d (Fig. 17). Despite the large ellipsoidal deformation of CB[10] upon complexation, the complexed porphyrins retain their fundamental UV/VIS, fluorescence, and electrochemical properties. The CB[ 10] porphyrin... 

TABLE 3.1 Relevant Physical Properties of the Cucurbit[n]uril Family of Hosts... 

Liu S, Ruspic C, Mukhopadhyay P, Chakrabarti S, Zavalij PY, Isaacs L. The cucurbit[n]uril family prime components for self-sorting systems. J Am Chem Soc 2005 127 15959-67. 

Reaction at the lower temperature gave a family of cucurbit[n]urils from pentamer to 11-mer, although their yields, except for cucurbit[6]urils, were low (10-25%). Fortunately, the new synthetic receptors, smaller or larger than cucurbit[6]uril, show good solubility (CB[5] ca. 420 mM CB[7] ca. 370 mM). Therefore, their discovery was a breakthrough in cucurbit[ ]uril chemistry, and has led to a rapid increase in research in this... 

One of the major applications of glycolurils is in the preparation of the cucurbituril family of molecular receptors. Despite being known for a number of years the popularity of this molecule has grown significantly in the last decade. The most common member of the cucurbituril family is cucurbit[6]uril containing six glycoluril units linked by methylene units 149 (Figure 6). 

The functionalization chemistry of the CDs has been extensively developed at this time.17 Synthetic methodology is available to either monofunctionalize or perfunc-tionalize either the primary or secondary hydroxyl portal of these hosts. Derivatiza-tion is still a pending subject in the chemistry of cucurbit[n]uril hosts. Kim and coworkers have reported a procedure that allows the equatorial functionalization of the periphery of CB6, but the same procedure is highly inefficient with either CB7 or CB8.18 Further developments in this area may be of great significance to extend the range of applications of this host family. 

This chapter focuses on the synthetic and supramolecular chemistry of the cucurbit[n]uril (CB[n] n = number of glycoluril units) family of macrocycles. Our research in this area, which began in 1998 at the University of Maryland, has been largely driven by our efforts to understand the mechanism of CB[n] formation. The chapter is therefore organized around that theme and is illustrated by subsequently developed applications of the CB[n] family. 

Table 1 General structures of cyclodextrin (left) and cucurbit[n]uril (right) receptors and relevant parameters for the most representative members of both host families...

Jeon WS, Moon K, Park SH, Chun H, Ko YH, Lee JY, Lee ES, Samal S, Selvapalam N, Rekharsky MV, Sindelar V, Sobransingh D, Inoue Y, Kaifer AE, Kim K (2005) Complexation of ferrocene derivatives by the cucurbit[7]uril host a comparative study of the cucurbitmil and cyclodextrin host families. J Am Chem Soc 127 12984-12989... 

Cucurbit[n]urils (CB[n]s) are a family of macrocyclic compounds comprising 5-10 gly-coluril units. CB[6], CB[7] and CB[8] are similar in cavity volume to a-CD, j8-CD and 7-CD, respectively. Differing from CDs, CBs are achiral host molecules of Dni, symmetry and therefore cannot provide chiral microenvironment. 

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