Syntheses and nickel coordination properties of cyclen substituted with mixed stilbene/poly(ethylene glycol) dendritic arms
Zhang, Q. Q.
- 医学院－已发表论文 
We synthesized a series of cyclens substituted with mixed stilbene and poly(ethylene glycol) dendritic arms. All dendrimers terminated with different peripheral groups had good solubility in common organic solvents, and dendrimers terminated with -CO2H groups (CO2H-dendrimers) were also soluble in alkaline solutions. The nickel coordination properties of these dendrimers were investigated in organic solvents. Dendrimers terminated with -CN groups (CN-dendrimers) and the second-generation CO2H-dendrimer [(CO2H)(8)L2] could produce pentacoordinated nickel complexes; the third-generation CO2H-dendrimer [(CO2H)(16)L3] could form tetra- and pentacoordinated nickel complexes, and the nickel complex of the fourth-generation CO2H-dendrimer [(CO2H)(32)L4] could not be obtained. This result was due to the fact that the globular surface Of (CO2H)(16)L3 formed a hydrogen-bond network that selectively penetrated cations and inhibited the access of anions to the core. The formation of the hydrogen-bond network was confirmed by Fourier transform infrared, H-1 NMR, and fluorescence data. The CN-dendrimers could not form hydrogen bonds on the surface, and the first- and second-generation CO2H-dendrimers could not form intramolecular hydrogen-bond networks. Therefore, they had no selectivity for positive nickel ions and negative chloride ions. (CO2H)(32)L4 could not produce a nickel complex because it had a crammed backbone structure that could not penetrate nickel and chloride ions. Therefore, it was possible to control the ion access of cations and anions with the hydrogen-bond network of (CO2H)(16)L3. (c) 2005 Wiley Periodicals, Inc.