Organometallic[bond]polyoxometalate hybrid compounds: metallosalen compounds modified by Keggin type polyoxometalates.
Hybrid compounds with two functional centers consisting of a metallosalen moiety (M[bond]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[bond]salen[bond]POM) it was shown by the use of a combination of UV[bond]vis, (1)H 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[bond]salen[bond]POM, the metallosalen center is best described as a metal[bond]salen cation radical species; that is, a localized "hole" is formed on the salen ligand. For the other M[bond]salen[bond]POM compounds, the metallosalen moiety can be described as a hybrid of a metal[bond]salen cation radical species and an oxidized metal[bond]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[bond]polyoxometalate acceptor) complexes despite the relatively large distance between the two functional centers.
Bar-Nahum
Itsik
I
Department of Organic Chemistry,Weizmann Institute of Science, Rehovot, Israel 76100.
Cohen
Hagai
H
Neumann
Ronny
R