Metal Complexes with Macrocyclic Ligands. Part XL. Syntheses and silver(I) complexes of mono‐ and disubstituted dithiadiazamacrocycles

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Abstract
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 properties towards Ag+ were studied by pH titrations and by potentiometry with a silver electrode. The observation that 1:1 ([AgLH2]3+, [AgLH]2+, [AgL]+) and 1:2 species ([AgL2H2]3+, [AgL2H]2+, [AgL2]+) were formed is interpreted by postulating that Ag+ can bind either to the S‐donors only, or to both the N‐ and S‐atoms. The most stable complex [AgL]+ in the series of the nonfunctionalized macrocycles was found for the 12‐membered N2S2‐ring 3. The stability of it increased when an additional donor group was introduced into the side chain. The highest formation constant (logβ110 = 14.43(1)) was obtained with the 12‐membered ring 12 carrying the ethanamine side chain. In view of a radiochemical application, all Ag+ complexes were tested in blood serum for their stability, but were not stable enough against transmetallation.

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