Stable Cu+, Ag+ complexes of aza-bridged macrocyclic molecules: structure and chemical properties

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Abstract
The cage type compounds 1 and 2 form stable Cu+ or Ag+ complexes, which have been employed for the preparation of cation-free host molecules.A reaction between the potassium complex K+⊂1 and a CuII salt generates a CuI complex. The CuII/CuI redox potential is observed at +0.43 V (vs. SCE) in the cyclic voltammetry, which shows that the Cu+ state is stabilized by its rigid molecular skeleton and spatially fixed coordination sites. A reaction between Ag+ and K+⊂2 yields the dinuclear complex 2Ag+⊂2, which has a short Ag+ · · · Ag + distance (2.78 Å). The halide anions (Cl-, Br-, I-) remove one Ag+ from 2Ag+⊂2 to give Ag+⊂2, but further demetallation does not occur. CV measurements show that these silver complexes are electrochemically stable. Both silver complexes are stable to sunlight. The first preparations of guest-free hosts have been achieved by treating Cu+⊂1 or 2Ag+⊂2 with CN-. Inclusions of neutral guests (NH3, BH3) have been attempted using these guest-free hosts.

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