Determination of the equilibrium constant for binding hydroxide to tetraazamacrocyclic—Nickel(II) complexes

Abstract The p K b for the equilibria NiL(OH) + ⇄ NiL 2+ + OH − for L1,4,7,10-tetraazacyclotridecane, 1,4,8, 12-tetraazacyclopentadecane, C-β-racemic-5,7,7,12, 14,14-hexamethyl-l,4,8,11-tetraazacyclotetradecane and C-β-racemic-1,4,5,7,7,8,11,12,14,14,-decamethyl- 1,4,8,112-tetraazacyclotetradecane are 0.95, 1.9, 0.2 and 0.65 respectively. The results are compared with data for analogous complexes reported earlier. The results indicate that the main factors affecting these equilibrium constants are the in plane ligand field strengths of the square planar complexes and steric factors.