METAL-COMPLEXES WITH MACROCYCLIC LIGANDS .40. SYNTHESES AND SILVER(I)COMPLEXES OF MONOSUBSTITUTED AND DISUBSTITUTED DITHIADIAZAMACROCYCLES

A series of N2S2-macrocycles with ring sizes varying between 12 and 16 , as well as two 12-membered N2S2-rings with a pendant carboxylic and amino group, respectively, were synthesized. Their complexation proper ties towards Ag+ were studied by pH titrations and by potentiometry wi th a silver electrode. The observation that 1:1 ([AgLH(2)](3+), [AgLH] (2+), [AgL](+)) and 1:2 species ([AgL(2)H(2)](3+), [AgL(2)H](2+) [AgL( 2)](+)) were formed is interpreted by postulating that Ag+ can bind ei ther to the S-donors only, or to both the N- and S-atoms. The most sta ble complex [AgL]+ in the series of the nonfunctionalized macrocycles was found for the 12-membered N2S2-ring 3. The stability of it increas ed when an additional donor group was introduced into the side chain. The highest formation constant (log beta(110) = 14.43(1)) was obtained with the 12-membered ring 12 carrying the ethanamine side chain. In v iew of a radiochemical application, all Agi complexes were tested in b lood serum for their stability, but were not stable enough against tra nsmetallation.