Optical and ESR studies on dimerization of metallotetra-crowned phthalocyanines
摘要:
The cation and solvent induced dimerization of free base tetra-crowned phthalocyanine (H2tCRPc) and its metal derivatives (Ag2+ and VO2+) have been studied by optical and ESR methods. Dimerization induces a blue shift of Q and Soret bands in the optical spectrum with a reduction in intensity. The exciton formalism accounts for the spectral blue shift upon dimerization. ESR studies reveal the formation of a cofacial dimer with axial symmetry upon the addition of cations. The measured zero-field splitting values in parallel and perpendicular regions suggest that the two paramagnetic centres are separated by 4.9 angstrom in VOtCRPc and 4.8 angstrom in AgtCRPc. In the micellar medium, the dimerization effects are observed only in 0.1 M SDS, while the tetra-crowned phthalocyanines remain aggregated in 0.1 M CTAB and in 5% TX-100.
Optical and ESR studies on dimerization of metallotetra-crowned phthalocyanines
摘要:
The cation and solvent induced dimerization of free base tetra-crowned phthalocyanine (H2tCRPc) and its metal derivatives (Ag2+ and VO2+) have been studied by optical and ESR methods. Dimerization induces a blue shift of Q and Soret bands in the optical spectrum with a reduction in intensity. The exciton formalism accounts for the spectral blue shift upon dimerization. ESR studies reveal the formation of a cofacial dimer with axial symmetry upon the addition of cations. The measured zero-field splitting values in parallel and perpendicular regions suggest that the two paramagnetic centres are separated by 4.9 angstrom in VOtCRPc and 4.8 angstrom in AgtCRPc. In the micellar medium, the dimerization effects are observed only in 0.1 M SDS, while the tetra-crowned phthalocyanines remain aggregated in 0.1 M CTAB and in 5% TX-100.