inorganic chemistry

For historical reasons, examples of case 2d, containing multi-

ple amine or amide groups in their branches, will be discussed

first. These types of dendrimers give rise to metal complexes of

variable stoichiometry and unknown structures since they con-

tain several more or less equivalent ligand units and not well-

defined coordination sites.

A. DENDRIMERS WITHMULTIPLECOORDINATIONSITES

A.1. Amide coordinating units

Dendrimer 3 (Fig. 7), which is based on a benzene core

branched in the 1, 3, and 5 positions, contains 18 amide groups

in its branches and 24 chromophoric dansyl units in the periph-

ery. It is well known that, in sufficiently basic solution, amide

groups ( 25 ), including the dansylamide units ( 26 ) can undergo

deprotonation and coordination of transition metal ions. The

dansyl units show strong absorption bands in the near UV

FIG. 7. Formula of a dendrimer containing 18 amide groups in its
branches and 24 chromophoric dansyl units in the periphery, capable
of coordinating metal ions (Co^2 þ, Ni^2 þ, or lanthanide ions), and the
corresponding scheme (Fig. 2d).

118 VINCENZO BALZANIet al.