COMPARTMENTALIZATION OF ZINC(II) TETRAPHENYLPORPHYRIN IN A HYDROPHOBIC MICRODOMAIN OF AN AMPHIPHILIC POLYELECTROLYTE - A PHYSICOCHEMICAL MODEL OF BIOLOGICAL METALLOPORPHYRIN SYSTEMS

Small mole fractions of zinc(II) tetraphenylporphyrin (ZnTPP) moieties were covalently incorporated into amphiphilic polysulfonates having bulky hydrophobic groups such as lauryl, cyclododecyl, and (2-naphthyl)methyl (Np) groups in their side chains. The ZnTPP moieties are ''compartmentalized'' in the hydrophobic domains of these amphiphilic polyelectrolytes in aqueous solution. For comparison, the ZnTPP moieties were covalently incorporated into a polysulfonate without hydrophobic groups. The ZnTPP moieties in this reference polymer are exposed to water in aqueous solution. The compartmentalized ZnTPP systems in aqueous fluid solution emitted phosphorescence and thermally activated delayed fluorescence at room temperature. This is due to an extremely long-lived triplet excited state in the compartmentalized systems at room temperature in aqueous solution, e.g. 19 ms for ZnTPP compartmentalized in Np domains, compared with 3 ms for ZnTPP in the reference polymer. These remarkable compartmentalization effects may be attributed to a restriction of motional freedom of the ZnTPP moiety isolated in a rigid and hydrophobic microenvironment provided by the amphiphilic polyelectrolytes in aqueous solution.