The synthesis of the terpyridinophane-type polyamine 2,6,9,12,16-pentaaza[17]-(5,5' ')-cyclo-(2,2':6',2' ')-terpyridinophane heptahydrobromide tetrahydrate (
L·7HBr·4H
2O) is described.
L presents six protonation constants withvalues in the range 9.21-3.27 logarithmic units.
L interacts with Cu
2+ and Zn
2+ forming in both cases, neutral,protonated, and hydroxylated mono- and binuclear complexes whose constants have been calculated by potentiometryin 0.15 M NaClO
4 at 298.1 K. The crystal structures of the compounds [Cu(H
L-carb)(H
2O)](ClO
4)
3·2H
2O (
1) and[Cu
2(H
2L)(CO
3)]
2(ClO
4)
8·9H
2O (
2) have been solved by X-ray diffraction. In
1, the metal center presents squarepyramidal geometry. The base of the pyramid is formed by the three nitrogen atoms of pyridine and one oxygenatom of a CO
2 group which is forming a carbamate bond with the central nitrogen atom of the polyamine chain.The axial position is occupied by a water molecule. In
2, one Cu
2+ is bound by the three pyridine nitrogens andthe other one by the three central nitrogen atoms of the polyamine chain. The square planar coordination geometryis completed by a carbonate group taken up from the atmosphere that behaves as a bridging
![](/images/entities/mgr.gif)
,
![](/images/entities/mgr.gif)
'-ligand betweenthe two centers. The pH-metric titrations on the ternary Cu
2+-
L-carbonate and Zn
2+-
L-carbonate systems showthe extensive formation of adduct species which above pH 6 are formed quantitatively in solution. The stoichiometriesof the main species formed in solution at pH = 6.8 agree with those found in the crystalline compounds. CO
2uptake by the Zn
2+ and Cu
2+ 1:1 complexes in aqueous solution has also been followed by recording the variationsin the band at ca. 300 nm. The formation of the Zn
2+ carbamate moiety has been evidenced by
13C NMR and ESIspectroscopy.