Department of Chemistry. Dr. H. S. Gour University. Sagar-470 003 Manuscript received 6 December 1993, revised 28 October 1994, accepted 8 November 1994 The formation constants (log \(K^{MA}_{MAL}\)) of mixed ligand complexes of the type [MAL] (where M = CII, NiII, CuII or ZnII; A = 2,2'-bipyridine; L = α-alanine (α-ala), valine (val), leucine (leu), iso-leucine (iso-leu) or nor­valine (nor-val) have been determined by SCOGS computer programme at 25, 35 and 45° and at I = 0.2 mot dm-3 (KNO3). The thermodynamic parameters (∆H and ∆S) of binary ML and ternary MAL complexes have been found to be favourable. The stability quantifying parameter ∆ log K becomes usually less negative at higher temperatures and the actual values of log \(K^{MA}_{MAL}\) increase with temperature. The ternary complexes are extrastabilised in solution. The extrastabilisation increases (i) in the order val < nor-val < leu -iso-leu, which is significantly the sequence of increasing length of non-coordinating hydrocarbon side-chain of the amino acids and (ii) also, in general, with temperature. Its extent depends on the nature of the metal ion and the geometry of the complex.