Complexation properties of some aminocarboxylate ligands containing in-chain phosphinate group

The complexation properties of the ligands bis(sarcosinato-N-methyl)-(L-1), bis(L-prolinato-N-methyl)- (L-2), bis(iminodiacetato-N-methyl) (L-3) and b is(morpholinato-N-methyl)phosphinic acid (L-4) were studied by pH-potentiom etric titration, by spectrophotometry and by H-1-NMR spectroscopy. The basi city of L-1, L-2, L-3 and L-4 is lower than that of the two composing ligan ds. However, the stability constants of complexes (logK(ML)) formed with Mg 2+, Ca2+, Cu2+, Zn2+ and some lanthanide(III) ions are in general higher (t he exceptions are the complexes CuL1 and CuL2) than the log beta(2) values of the sarcosinate, L-prolinate and iminodiacetate complexes, indicating th e participation of the phosphinate group in complexation. ML3 are particula rly high and the AB multiplet pattern of the H-1-NMR spectrum of ZnL3 shows the rigid structure of the complex.