ZINC(II) COMPLEXES OF DIPROPYLENETRIAMINE AND N-(2-AMINOETHYL)PROPANE-1,3-DIAMINE - A C-13 NUCLEAR MAGNETIC-RESONANCE STUDY

Carbon-13 n.m.r. spectra are reported as a function of pH for mixtures of dipropylenetriamine (dpt) or N-(2-aminoethyl)propane-1,3-diamine (aepn) and zinc nitrate, of zinc and dpt or aepn with 1,2-diaminoethane (en), 1,3-diaminopropane (pn), and glycine (gly), and of zinc and aepn with L-alanine (ala), .beta.-alanine (.beta.-ala), and trans-1,2-diaminocyclohexane (dach). Carbon-13 chemical shifts are also reported as a function of pH for dpt, .beta.-ala, and dach alone. The pH profiles have been analysed by computer and chemical shifts determined for the following species: dpt, Hdpt+, H2dpt2+, H3dpt3+, .beta.-alaO, .beta.-ala, dach, Hdach+, H2dach2+, [Zn(dpt)]2+, [Zn(dpt]2+, [Zn(dpt) (Hdpt]3+, [Zn(dpt)2]2+, [Zn(dpt)(OH)]+, [Zn(dpt)(en)]2+, [Zn(dpt)(glyO)]+, [Zn(aepn)]2+, [Zn(aepn)(Haepn)]3+, [Zn(aepn)2]2+, [Zn(aepn)(OH)]+, [Zn(aepn)(en)]2+, [Zn(aepn)(pn)]2+, [Zn(aepn)(dach)]2+, [Zn(aepn)(glyO)]+, [Zn(aepn)(ala))]+, and [Zn(aepn)(.beta.-alaO)]+. Stability constants have also been determined for the bis and ternary complexes. Potentiometric titrations with dpt, zinc+dpt, and zinc+aepn solutions provide support for the interpretation of the chemical shift data. The results are compared with those of a previous study with diethylenetriamine and used to provide evidence concerning the co-ordination geometry of zinc in these complexes.