Photoresponsive Crown Ethers. 13. Synthesis of Photoresponsive NS2O Crown Ethers and Application of the Cu(I) Complexes to O2-Binding

Abstract

Abstract Photoresponsive crown ethers with heavy metal affinity were synthesized: They are the NS2O crowns bound to photofunctional azobenzene at 4,4′-positions via X(CH2 or CO) (1(X=CH2) and 1(X CO), respectively). They efficiently extracted heavy metal ions from aqueous phase to organic(dichloromethane) phase. The continuous variation method established that both trans-1 and photoisomerized cis-1 bind two Cu(II) ions forming 1:1 metal/NS2O crown complexes. The trans-1(X=CH2)·Cu(I)2 complex was irreversibly oxidized by O2 to the Cu(II)2 complex, whereas the cis-1(X=CH2)·Cu(I)2 complex bound O2 in a partly reversible manner like Osborn’s complex. Thus, a photoinduced change in the Cu(I)·····Cu(I) interatomic distance is responsible for the stability of the O2 complex. These results show that the extraction of heavy metal ions and the O2-complexation can be controlled by light with the mediation of photoresponsive NS2O crown ethers.