A New Parameter in Astatistical Stabilization of Ternary Complexes

Department of Chemistry, Faculty of Science, M. S. University of Baroda, Baroda-390 002

The formation constants of the complexes of the type [CuAL], where A -2',^­bipyridyl (bipy), 1,10-phenanthroline (phen) and L tryptophan have been determined in aqueous medium and in - 0.2 M (NaClO₄) at 30°. The formation constant values have been determined by graphical method and further refined by using a computer program SCOGS. The value of ∆ log K, (log $K_{MAL}^{ML}$-log $K_{ML}^M$), is found to be positive. in [CuAL] complexes even though L is coordinating through amino acid end just as glycine ­The higher stabilization of the ternary complexes is mainly due to release of electron. repulsion in the ternary complex. There is repulsion between Cu(II) der electrons and electrons delocalized over the indole ring in binary complex. In the ternary complele, due to M→bipy π interaction, electrons pass over the bipyridyl molecule and there is less amount of electron repulsion leading to positive ∆ log K.