Hybrid compounds with two functional centers consisting of a metallosalen moiety (M-salen; M = Mn, Co, Ni, and Pd) connected by an alkylene bridging group to a lacunary Keggin type polyoxometalate were synthesized and characterized. In these metallosalen-polyoxometalate compounds (M-salen-POM) it was shown by the use of a combination of UV-vis, 1H NMR, EPR, XPS, and cyclic voltammetry measurements that the polyoxometalate exerts a significant intramolecular electronic effect on the metallosalen moiety leading to formation of an oxidized metallosalen moiety. For the Mn-salen-POM, the metallosalen center is best described as a metal-salen cation radical species; that is, a localized "hole" is formed on the salen ligand. For the other M-salen-POM compounds, the metallosalen moiety can be described as a hybrid of a metal-salen cation radical species and an oxidized metal-salen species, that is, a delocalized "hole" is formed at the metallosalen center. It is proposed that these oxidized metallosalen centers are best characterized as stabilized charge transfer (metallosalen donor-polyoxometalate acceptor) complexes despite the relatively large distance between the two functional centers.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry