Synthesis, electrochemical and photophysical properties of covalently linked porphyrin-polyoxometalates

Two covalently linked porphyrin-polyoxometalate hybrids have been prepared: an Anderson-type hexamolybdate [N(C4H9)(4)](3)[MnMo6O18{(OCH2)(3)CNHCO(ZnTPP)}(2)] with two pendant zinc(II)-tetraphenylporphyrins, and a Dawson-type vanadotungstate [N(C4H9)(4)](5)H[P2V3W15O59{(OCH2)(3)CNHCO(ZnTPP)}] with one porphyrin. Electrochemical studies show independent redox processes for the organic and inorganic parts at usual potentials. Photophysical studies reveal an electron transfer from the excited porphyrin to the Dawson polyoxometalate, but not to the Anderson polyoxometalate. Time resolved absorption spectroscopy allows the identification of the electron transfer pathways and the determination of the time constants.