In order to investigate the stoichiometry and stability of a Li+ complex with new heptadentate (N7) macrocyclic Schiff base having two pyridyl units as pendant arms (MSb) in Acetonitrile and Methanol mixture (50:50), Lithium-7 NMR spectroscopy was employed. A competitive 7Li NMR method was also used to probe the complexation of Li+, Na+, K+, Rb+, Mg2+, Ca2+, Ba2+, Mn2+, Zn2+ , Cd2+ and UO2 2+ ions with macrocyclic Schiff base (MSb) in the same solvent systems. The formation constants were evaluated from computer fitting of the mole ratio data to an equation that relates the observed chemical shifts to the formation constant of the resulting complexes. In this solvent, the stability of the final 1:1 complexes were found to vary in the following order: Zn2+-MSb > Mn2+-MSb > Cd2+-MSb > UO2 2+-MSb > Ca2+-MSb > Mg2+-MSb > Na+-MSb > Li+-MSb > Ba2+- MSb > K+-MSb > Rb+-MSb.
