ANOMALOUSLY BLUE-SHIFTED FLUORESCENCE AND PHOSPHORESCENCE OF ZINC(II)TETRAPHENYLPORPHYRIN IN HIGHLY CONSTRAINING MICROENVIRONMENTS IN HYDROPHOBICALLY-MODIFIED POLYSULFONATES

Zinc(II) tetraphenylporphyrin (ZnTPP) moieties, covalently attached to amphiphilic sodium polysulfonates carrying cyclododecyl (Cd; 60 mol % ) or lauryl (La; 61 mol %) groups, are compartmentalized within the cl usters of the hydrophobic groups in aqueous solution. Such compartment alized ZnTPP chromophores exhibit delayed fluorescence and phosphoresc ence at ordinary temperatures. The spectral patterns of the fluorescen ce and phosphorescence of the ZnTPP moieties in the Cd cluster strongl y depended on the excitation wavelength; anomalously blue-shifted fluo rescence (both prompt and delayed) and phosphorescence spectra were ob served when excited at wavelengths on the shorter wavelength side of t he Soret band maximum, while these emissions showed normal spectra whe n excited at wavelengths on the red side of the Soret band maximum. No such dependencies of the emission spectra on the excitation wavelengt h were recognized for the ZnTPP moieties compartmentalized in the La c luster. The spectral data indicate that the microenvironment about the ZnTPP chromophores in the Cd cluster is markedly different from that in the La cluster and that there are ZnTPP species whose electronic en ergy levels are considerably perturbed in the Cd cluster. These specie s are ascribed to conformationally distorted ZnTPP species owing to th e highly constraining microenvironments in the Cd cluster.