Stability constants of complexes of divalent and rare earth metals with substituted salicynals

5-Chloro-4-6-dimethyl-salicylaldehyde was synthesized from 4-chloro-3,5-dim ethyl-phenol. A series of substituted salicynals were obtained by condensat ion of 5-chloro-4,6-dimethyl-salicylaldehyde with several amines. The amine s were chosen such as to vary the basicity of salicynals by changing the su bstituents at one of the coordination sites. The stability constants of com plexes of bivalent (Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+) and trivalent (Y3+, La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Er3+, Yb3+) metal ions wit h these salicynals and the pK values corresponding to the dissociation of t he phenolic proton and the association of a proton to the azomethine nitrog en were determined potentiometrically using the Calvin-Bjerrum technique as adopted by Irving and Rossotti at 303 K and a constant ionic strength of 0 .1 M in a 75:25 (v/v) dioxan-water mixture in an inert atmosphere. The infl uence of substituents on the proton affinity of the ligands was examined on the basis of inductive and mesomeric effects. It is also shown that some o f the complexes possess antibacterial, antitubercular, antifungal, and anti coagulant activity.