Formation of a new hybrid complex via coordination interaction between 5,10,15-tritolyl-20-(4-and 3-pyridyl)porphyrin or 5,10,15-triphenyl-20-(4-pyridyl)porphyrin and the alpha-[MSiW11O39](6-) Keggin-type polyoxometalate (M = Co2+ and Ni2+)
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Indexed by: Journal Article
Date of Publication: 2010-06-20
Journal: INORGANICA CHIMICA ACTA
Included Journals: SCIE
Volume: 363
Issue: 10
Page Number: 2185-2192
ISSN: 0020-1693
Key Words: Hybrid complexes; Porphyrin; Polyoxometalate; Paramagnetic H-1 NMR; Steady-state and time-resolved luminescence
Abstract: New complexes based on a coordination interaction between a pyridyl-porphyrin (namely 5,10,15-tritolyl-20-(4-pyridyl)porphyrin, 5,10,15-tritolyl-20-(3-pyridyl)porphyrin or 5,10,15-triphenyl-20-(4-pyridyl)porphyrin) and a Keggin-type polyoxometalate (alpha-[MSiW11O39](6-), M=Co2+ or Ni2+) are formed in solution. The formation of these complexes is clearly evidenced by steady-state and time-resolved luminescence measurements. A strong quenching of the porphyrin fluorescence, accompanied by an important shortening of the fluorescence lifetime, is observed upon addition of the POM and formation of the complexes. Using a variant of the Job's method from the luminescence spectra, the association constants of the complexes have been estimated to be around 10(6) L mol(-1). Paramagnetic H-1 NMR experiments confirm the formation of the complexes. Indeed, in addition to broadenings of the signals, the coordination binding of the POM to the porphyrin induces large high-frequency shifts for the protons of the pyridyl group coordinated to the paramagnetic metal, and low-frequency shifts for all the other resonances. (C) 2010 Elsevier B.V. All rights reserved.