We have synthesized a novel dendrimer (1) based on two covalently linked cyclam units as a core appended to six branches, each one consisting of one dimethoxybenzene and two naphthyl units (cyclam = 1,4,8,11-tetraazacyclotetradecane). Such a dendrimer shows three fluorescence bands which can be assigned to naphthyl localized excited states (λmax
= 336 nm), naphthyl excimers (λmaxca. 390 nm), and naphthyl–amine exciplexes (λmax
= 510 nm). Protonation or complexation of the bis-cyclam core with Zn2+ does not affect the absorption spectrum of the dendrimer, but causes noticeable changes in the fluorescence intensity of the three component bands. Complexation with Cu2+ not only causes changes in the relative intensities of the fluorescence bands, but also the appearance of a new absorption band in the near UV spectral region. Analysis of the titration curves has allowed us to obtain clear evidence for the formation of 1 : 1 (1(H+), [Zn(1)]2+, [Cu(1)]2+) and 2 : 1 (1(2H+), [Zn2(1)]4+, [Cu2(1)]4+) species. Comparison with the behaviour of a previously investigated parent monocyclam dendrimer (2) suggests that in the 1 : 1 species of 1 both the cyclam units are involved in the complexation with Zn2+ and Cu2+.
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