The effects of polyammonium macrocycles on the spectroscopic and photochemical properties of the Co(EDTA)- . I- ion-pair have been investigated. The addition of a macrocycle to aqueous solutions containing Co(EDTA)- and I- causes an increase of the absorbance in the region of the ion-pair charge-transfer band, as well as an increase of the quantum yield for the intramolecular photooxidation reduction of the ion-pair. Both these effects are mainly, if not only, due to an increase of the association constant between Co(EDTA)- and I-, caused by the positive charge of the macrocycle bound to the complex. On the contrary no change was observed on the intrinsic photoreactivity of the excited ion-pair. This last result is discussed in comparison with the effects already observed on the ligand photodissociation of MC excited states of Co(III) cyanide complexes.

The photochemistry of aqueous solutions of [Co(CN)5H2O]2- in the presence of the polyammonium macrocyclic receptor [32]ane-N8H88+ was studied. The quantum yield for cyanide release in free [Co(CN)5H2O]2- (PHI = 0.003 at 313 nm, pH 1.5) is reduced approximately threefold in the presence of the protonated macrocycle, which provides evidence for the formation of a supramolecular structure. Further evidence for the supramolecular structure is obtained from the thermal anation of [Co(CN)5H2O]2- with Br- (40-degrees-C, pH 1.0), the rate of which is increased in the presence of [32]ane-N8H88+, suggesting that the ligand water is not involved in hydrogen bonds with the macrocycle. These results are interpreted in terms of possible supramolecular structures.

The absorption and excited state properties of 9-cyanoanthracene are strongly modified upon inclusion into an octaimine hemicarcerand; the walls of the host do not transfer excitation to the guest and quench its fluorescent excited state.