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Solution equilibrium studies on Cu-L-L ternary systems have been performed by pH-potentiometry, UV-Vis spectrophotometry and EPR methods (L corresponds to polyamines such as ethylenediamine (en), diethylenetriamine (dien), or N, N, N′, N′, N″-pentamethyldiethylenetriamine (Medien) and L represents 1-aminoethylphosphonic acid ( α-alaninephosphonic acid)). The obtained results suggest the formation of heteroligand complexes with [Cu(L)( α-Ala(P))] stoichiometry in all studied systems. Additionally, in the system with en the [Cu(en)( α-Ala(P))H] species is formed in basic solution. Our spectroscopic results indicate tetragonal geometry for the [Cu(en)( α-Ala(P))] species, geometry slightly deviated from square pyramidal for the [Cu(dien)( α-Ala(P))] complex and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Medien)( α-Ala(P))] species. The coordination modes in these heteroligand complexes are discussed. [ABSTRACT FROM AUTHOR]