Multi-armed cyclams

Tsukube 14) reported in 1984 a multi-armed cyclam (18) which has the ability to transport NH4+ cation through a chloroform layer (a so-called liquid membrane ). Metal ions such as K+ are not transported under similar conditions, a selectivity generally unobserved with the common crown ethers and cryptates. Since the transport rate decreases substantially when the furan rings terminating the pendant arms are... 

Multi-armed cyclams" were also obtained from cyclam (Strem). Cyclam (1,4,8,11-tetraazacyclotetradecane) was condensed with 2-furoyl chloride, and the resultant tetraamide was reduced by diborane in THF. Recrystallization from ether-hexane gave colorless crystals 2. Mp, 83-84 C. Elemetal analysis Calcd. C 69.20, H 7.74, N 10.76. Found ... 

As a new series of "open-chain cryptands", "multi-armed cyclams" were designed and employed in the cation transport experiments. Parent polyamine macrocycle (cyclam) is well known to show somewhat different cation binding properties from those of macrocyclic polyethers. It effectively bind ammoniiim cations via strong hydrogen bonding as well as transition metal cations via coordination interaction. Hence, new "multi-armed cyclams" are expected to exhibit unique cation transport abilities. Their cation transport results are summarized in Table 3. 

Table 3. Membrane Transport Mediated by "Multi-Armed Cyclams"...

Multi-armed cyclam" bearine furan oxygen atoms on its four arms mediated specific transport of NH cation across a liquid membrane, while H, K, and other metal cations were hardly transported under the employed conditions. Since simple cyclam derivatives fi and exhibited low transport rates of NH cation, the furan oxygen atoms attached to the cyclam ring may play an important role in complexation and transportation of NH cation. ... 

H.Tsukube, Multi-Armed Cyclam For Specific Transport of NH Cation ... 

---