Thermodynamic, NMR and photochemical study on the acid-base behaviour of N,N'-dibenzylated polyamines and on their interaction with hexacyanocobaltate(III)

The synthesis and protonation behaviour of the dibenzylated open-chain ligands 1,4-dibenzyl-1,4-diazabutane (L(1)), 1,7-dibenzyl-1,4,7-triazaheptane (L(2)), 1,10-dibenzyl-1,4,7,10-tetraazadecane (L(3)), 1,12- dibenzyl-1,5,8,12-tetraazadodecane (L(4)) and 1,13-dibenzyl-1,4,7,10,13-pentaazatridecane (L(5)) are presented. The protonation behaviour has been studied by means of pH-metric measurements, NMR, absorption UV-VIS and steady-state fluorescence emission spectroscopy The influence of the aromatic ring on the acid-base behaviour of these ligands is discussed. The association constants of these ligands with [Co(CN)(6)](3-) have been calculated by steady-state fluorescence emission. The reduction in the quantum yield for the photoaquation reaction of [Co(CN6)](3-) in the presence of L(5) suggests that three out of the six cyanide groups of the anion are involved in the formation of the hydrogen-bond network of the supramolecular adduct.