Encapsulated anions

Kim H, Akagi T, Akashi M (2010) Preparation of CpG ODN-encapsulated anionic poly (amino acid) nanoparticles for gene delivery. Chem Lett 39 278-279... 

The nucleophilic property of the encapsulated anion was dramatically changed compared to the free anion. Thus, [2-Ag4(/U-Cl)4(/U4-Cl)] acts as a nucleophile to convert alkyl-iodide to alkyl-chloride in high yield. Puddephatt proposed a mechanism where the [2-Ag4(/U-Cl)4(/U4-Cl)] anion reacts with alkyl-iodide to give [2-Ag4(/z-Cl)4(/U4-I)] and alkyl-chloride. The reaction occurs in high yield with the reactivity sequence tertiary>second-ary>primary alkyl. 

In the previous section it was noted that hexacyclen 1 does not possess a macrocyclic cavity of sufficient size to encapsulate anionic guests such as Cl" and NO3. In contrast, the octaaza macrobicyclic analogue of hexacyclen (17) forms the fluoride cryptate [F" c 17-6H ] (Figure 7). Consistent with the observed high... 

An example of the above mentioned cascade complexation of carboxylates by macrocyclic receptors containing metal ionic centers is the inclusion of oxalate by the dien dicobalt complex 9 (Martell, Mitsokaitis) [12]. Similarly, the -cyclodextrin (jS-CD) 10, modified with a zinc cation bound by a triamine side chain, encapsulates anions like 1-adamantylcarboxylate in its cavity, fixing them by combined electrostatic and hydrophobic interactions [13], Zinc s group achieved the enantioselective transport of the potassium salts of N-protected amino acids and dipeptides by making use of the cation affinity of... 

Figure 3.4 Stick representations of complexes 24 (a) and 33 (b), including the encapsulated anions and their interactions. Distances are in A.

The pioneering work of Lehn established the fundamental strategy of using preformed three dimensional cage ligands, dubbed cryptands, to ensure enhanced thermodynamic and kinetic stability for cation complexation [1], Positively charged cryptands, typically the N-donor azacryptands, can also serve to encapsulate anions. 

Earlier discussion [12] of the structures of protonated cryptand/oxoanion assemblies was based on consideration of H-bonds between the encapsulated anion and the NH+ donors of the ciyptand. These interactions are assumed to be responsible for retention of the guest anion in the host ciyptand cavity, both in the sohd state and in solution. We have shown that, in all cases, anion cryptates exhibit at least three, and often more, direct H-bond NH+-Oanion contacts tethering the included oxoanion within the crypt. 

In our attempts to design functional clusters we have focused on substitution of the heteroanions within the Wells-Dawson structure to create nonconventional Dawson clusters incorporating two pyramidal anions. Our design rationale was based on the idea that such clusters may exhibit unprecedented properties arising from the intramolecular electronic interactions between the encapsulated anions (in this case we aimed to engineer between S S atoms of two encapsulated sulfite ions), thus providing a novel route to manipulate the physical properties of... 

Fig. 12 A helical Pd based cage and its solid state encapsulation of PFg, (non-encapsulated anions are not shown for clarity)...

Fig. 17a,b The crystal structures of a [Ni4(20)4(CH3CN)8] [BF4]8, templated around the central anion b the [Ni5(20)5(CH3CN)10][SbF6]10 pentagon, non encapsulated anions and hydrogen atoms are not shown... 

Fig. 18 a The tetrahedral Co and b bridged Ni compounds of 21, non-encapsulated anions and hydrogen atoms omitted for clarity... 

Cationic amphiphilic CDs, heptakis[2-co-amino-0-oligo(ethylene oxide] hexyl-thio-ji-CD nanoparticles, have encapsulated anionic porphyrins (TPPS) by entangling these molecules within the aliphatic chains aligning both faces of the cationic amphiphilic CD. These nanoparticles were demonstrated to preserve the photodynamic properties of the entrapped photoactive agent. The photodynamic efficacy of the carrier/sensitizer nanoparticles was proven by in vitro studies on tumor HeLa cells showing significant cell death upon illumination with visible light [88]. 

Ni5(bptz)5(CH3CN)io cShF6 with the encapsulated anion... 

Carbon atoms in fullerenes possess an sp--type electronic configuration, but, in contrast with graphitic carbons, addition reactions at the double bond junction between six-membered rings are allowed. This is due to the pyramidalization of s T carbons as a result of the curvature of the structure (Bard et al., 2008). Accordingly, a variety of functionalized fullerenes can be prepared (Hirsch, 1993). In addition, fullerenes can encapsulate anions and neutral molecules, thus forming the so-called endohe-dral fullerenes (Guha and Nakamoto, 2005) and form different types of polymeric chains. 

Fig. 7 X-ray crystal structure of [Co2(L )4(MeCN)2C(BF4)](Bp4)3 showing the encapsulated anion and its interactions with the metal centres...

Sections 18, 19, and 20 are concerned with compounds based upon or derived from W 03. cages plus encapsulated anions and thus are related to the [W.oOsa], [SiW.jO o] ", and [PW.jO ] " com-... 

A series of well-defined macrocyclic polyethers (crown ethers) have been synthesized by Pedersen (1, 2), who also demonstrated the capability of com-plexing and lipophilizing alkali metal ions. The KMn04-18-crown-6 complex (1) is soluble in benzene (3). Potassium metal is solubilized by a dinaph-thalenated cyclic polyether to form the interesting K -encapsulated anion radical (2) (4). 

Confined nanospaces in metaUocages Guest molecules, weakly encapsulated anions, and catalyst sequestration 12CRV2015. 

---