Designing diverse coordination modes for the covalent attachment of Wells-Dawson type polyoxometalate onto porphyrins

Five covalently bonded polyoxometalate (POM)-porphyrin hybrids were synthesized by reacting the Wells-Dawson type polyoxometalate [N(C4H9)(4)](5)H4P2W15V3O62 with five tris-functionalized porphyrins containing different numbers of tris groups at different peripheral positions. These hybrids were thoroughly characterized using elemental analysis, NMR (H-1, P-31, and V-51), mass spectrometry (ESI-MS, MALID-TOF-MS), FT-IR, UV-Vis, and fluorescence spectroscopies. The results proved that different quantities (one, two, and three) of the vanadium-capped Wells-Dawson type metal-oxide cluster P2W15V3O629- can be grafted onto a porphyrin moiety via covalent bonding with different orientations, depending on the number and position of peripheral functional groups on the porphyrin. Interestingly, remarkable fluorescence quenching (60% in 3Py-P@1POM, 75% in trans-2PyP@2POM, 80% in cis-2PyP@2POM, 85% in cis-2PhP@2POM, and 55% in 1Py-P@3POM, as compared to the fluorescence intensity of their corresponding porphyrin precursor) was observed under excitation (& lambda;(exc) = 328 nm), indicating electron transfer from the porphyrin moiety to the POM moiety through covalent linkage.

Automated summary

Five covalently bonded polyoxometalate (POM)-porphyrin hybrids were synthesized by reacting different tris-functionalized porphyrins with the Wells-Dawson type polyoxometalate. Characterization of these hybrids using various techniques confirmed the formation of the hybrids and the electron transfer from the porphyrin moiety to the POM moiety through covalent linkage.