The chemical properties of the monovalent nickel complexes, NiLi+, where L1 = 1,4,7,10 tetraazacyclotridecane and L3 = 1,4,8,12 tetraazacyclopentadecane, in aqueous solutions were studied electrochemically and pulse‐radiolytically. The results are compared with those for L2 = 1,4,8,11 tetraazacyclotetradecane which were earlier reported. The redox potentials for the NiLi2+/NiLi+ couples are < −1.70, −1.56 and −1.50 V vs. Ag/AgCl for L1, L2 and L3 respectively. NiL+2 has the longest half‐life in neutral solutions, ca 2 s and NiL1 the shortest ca 100 μs. NiL+1 and NiL+2 react with N2O to yield NiLi3+ in fast reactions; this reaction cannot be studied for NiL+3. CO−2 radicals reduce NiL2+1 and NiL2+2 in a reaction approaching the diffusion controlled limit via the bridged mechanism. No reaction between CO−2 and NiL3(H2O)2+2 is observed.