Spectrophotometric characterization of diazacrown ethers having two carbodithioate groups

Diazacrown ethers having two carbodithioate groups were synthesized, and their spectrophotometric properties were studied. Diammonium 1,4,10,13-tetraoxa-7,16-diazacycrooctadecane-N,N'-bis(carbodithioate) (DA18CC) and ammonium 1,4,10-trioxa-7,13-diazacycropentadecane-N,N'-bis(carbodithioate) (DA15CC) reacted with most heavy-metal ions through their two carbodithioate groups, and also reacted with alkali-metal ions or alkaline earth-metal ions through their diazacrown rings. Although the UV-VIS absorption spectra of DA18CC and DA15CC were hardly influenced by the addition of alkali-metal ions or alkaline earth-metal ions, the spectra of some heavy-metal chelates of DA18CC and DA15CC were influenced. The composition ratio (metal:ligand) of Cu(II) and Pb(II) chelates of DA18CC and DA15CC was altered from 1:1 to 1:2 by the addition of alkali-metal ions or alkaline earth-metal ions. It is suggested that the change in the absorption spectra and the composition ratio of the chelates can be attributed to an alteration of the equilibrium among species of the heavy-metal chelates of DA18CC and DA15CC due to the coordination of alkali-metal ions or alkaline earth-metal ions into the diazacrown ring.