Stability studies on 12-(5'-8'-hydroxyquinolinic)methylene-1,4,7,10- tetraazacyclo tridecane-11,13-dione, 5- substituted 1,10-phenanthroline-copper(II) with Cu²⁺ or Co²⁺ binuclear mixed coordinated systems

Abstract

C-functionalized dioxotetraamine ligands L have been designed and synthesized through simple methods, and characterized by elemental analysis, IR, mass spectra and ¹H NMR. The ligand contains two independent chelating groups. At 25.0±0.1^oC, I=0.1 mol·dm^-3 NaNO₃, <i>p</i>H titration has been performed to study the stability properties of L-5-R-5,10-phenanthroline-Cu(II) with proton, copper(II) and cobalt(II). The ternary complexes have been shown to possess interesting properties due to the involvement of three chelating groups, 5-substituted- 1, 10-phenanthroline, 8- hydroxyquinoline and dioxotetraamine. In addition, potentiometric titrations have been performed to study the protonation of L-5-R- 1, 10-phenanthroline-Cu(II) (R=CH₃,H,Cl,NO₂) and their stability

properties with copper(II) and cobalt(II). The results show that for Cu²⁺ and Co²⁺, 8-hydroxyquinoline is a strong chelating reagent than dioxytetraamine macrocycles. Using molecular mechanics (MM⁺) calculation, the stability of ternary mixed system on Co(II)L- S-substituted- 1, 10-phenanthroline-Cu(II) and Cu(II)-L-Ssubstituted-1, 10-phenanthroline-Cu(II) have been studied and compared with the coordination ability for different coordination sites and for different metal ions (Co(II) and Cu(II) at the same coordination site. The results obtained from calculation agree with the experimental results.