Ring Size Effect on the Chemical Properties of Monovalent Nickel Complexes with Tetraazamacrocyclic Ligands in Aqueous Solutions

The chemical properties of the monovalent nickel complexes, NiLi + , where L 1 = 1,4,7,10 tetraazacyclotridecane and L 3 = 1,4,8,12 tetraazacyclopentadecane, in aqueous solutions were studied electrochemically and pulse‐radiolytically. The results are compared with those for L 2 = 1,4,8,11 tetraazacyclotetradecane which were earlier reported. The redox potentials for the NiLi 2+ /NiLi + couples are < −1.70, −1.56 and −1.50 V vs. Ag/AgCl for L 1 , L 2 and L 3 respectively. NiL + 2 has the longest half‐life in neutral solutions, ca 2 s and NiL 1 the shortest ca 100 μs. NiL + 1 and NiL + 2 react with N 2 O to yield NiLi 3+ in fast reactions; this reaction cannot be studied for NiL + 3 . CO − 2 radicals reduce NiL 2+ 1 and NiL 2+ 2 in a reaction approaching the diffusion controlled limit via the bridged mechanism. No reaction between CO − 2 and NiL 3 (H 2 O) 2+ 2 is observed.