Lariat ether amides

Figure 4. Lariat Ether Amide and Thioamide Carriers.

Transport rates for the five alkali metal perchlorates across bulk chloroform membranes by lariat ether amides 17-28 are presented in Table 3. In all cases, transport of li um, rubidium and cesium perchlorates was undetectable. The Na /K" transport selectivities calculated from the single species transport rates are also given in Table 3. 

Table 3. Transport of Alkali Metal Perchlorates by Lariat Ether Amides 17-28...

The difference in Na /K transport selectivities for the N,N-di(propyl) through N,N-di(hexyl) members of the two series of lariat ether amides is striking. Thus the selectivity of 2-3 which is calculated for the N,N-dialkyl 5yw-dibenzo-16-crown-5-oxyacetamides increases to the range of 40-60 for the N,N-dialkyl sym (propyl)dibenzo-16-crown-5-oxyacetamide analogues. Conformational differences of the amide-containing side arms in the two series is proposed as the causitive factor. 

For alkali metal cation transport across bulk chloroform membranes by lariat ether amides based upon dibenzo-16-crown-5 rings, preorganization of the coordinating side arm over the polyether cavity enhances both the efficiency and selectivity of Na transport. For the corresponding lariat ether thioamides, efficient transport of Ag", but not the alkali metal cations, is observed. In this case, preorganization of the side arm is detrimental which indicates predominant coordination of the soft Ag" with the soft sulfur atom of the thioamide group. 

Alkali metal perchlorate transport lariat ether amides, 161-164 lipophilic 18-crown-6 and 15-crown-5 derivatives, 157-160... 

Thermodynamic parameters derived from calorimetry for metal ion binding by a range of aza-oxa lariat ethers and BiBLE s with amide side arms (3.52 and 3.53) is shown in Table 3.7. Coordination occurs via the macrocycle and amide oxygen atom. The longer chain side arms 3.52b and 3.53b are... 

Table 3.7 Thermodynamic data for amide lariat ethers (methanol, 25 °C), 15...

Transport of Metal Perchlorates by Lariat Ethers Based on Dibenzo-16-crown-5 Compounds with Amide- and Thioamide-Containing Side Arms. 

We have developed efficient syntheses of. /w-(hy(iroxy)dibenzo-16-crown-5 and jyw-(alkyl)(hydroxy)dibenzo-16-crown-5 compounds 17,18). These lariat ether alcohols, in which the alcohol function and a hydrogen atom or alkyl group are attached to the central carbon of the three-carbon bridge serve as platforms for attachment of various potential coordinating groups to provide a variety of other lariat ether compounds. For example, dibenzo-16-crown-5 lariat ethers with pendent amide 19), ester 20) and thioamide (27) groups have been prepared. To further probe the effect of structural variation within lariat ethers, studies of metal perchlorate transport across bulk chloroform membranes by dibenzo-16-crown-5 lariat ethers with oxyacetamide and oxythioacetamide side arms were undertaken. 

For the carriers 29-42, the transport of potassium perchlorate was uniformly low or undetectable. On the other hand, the lariat ether thioamides exhibit a propensity for transport of Ag" across bulk chloroform membranes. Thus substitution of the amide oxygen in a dibenzo-16-crown-oxyacetamide by sulfur to produce the corresponding thioamide transforms an effective Na carrier into an efficient Ag" ... 

Gokel for reducible quinone (25, 26) and nitroaromatic (32, 33) lariat crown ethers with alkali metal guest cations discussed earlier. Support for the latter effect comes from the related ligand system (81), containing no amide carbonyl groups, and electrochemical results revealing... 

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