Formation of Alkaline Earth and Transition Metal Complexes with Efavirenz Drug in Ethanol-Water Media

The stability constant of Efavirenz drug with alkaline earth metal ions Mg(II), Ca(II) and transition metal ions Fe(III), Cu(II) were investigate using pH metric titration technique in 20%(v/v) ethanol-water mixture at 27 °C temperature and at an ionic strength of 0.1M NaClO4.{Metal to ligand ratio = 1:5 & 1:1}The method of Calvin and Bjerrum as adopted by Irving and Rossotti has been employed to determine proton ligand (pKa) and metal-ligand stability constants (log K) values. It is observed that alkaline earth metal & transition metal ion forms 1:1 and 1:2 complexes. The order of stability constants for these metal complexes was as: Fe3+ > Cu2+ > Mg2+ > Ca2+