Funktionalisierung von Polyoxowolframaten im Kontext der molekularen Spintronik
Herstellung und Eigenschaften von Funktionsmaterialien
Zusammenfassung der Projektergebnisse
Bi-functionalization of discrete polynuclear WVI oxo complexes known as polyoxotungstates (POTs) with heterometal ions and organic groups offers broad perspectives for the fine-tuning of their electronic properties, solubility, reactivity as well as an ability to be controllably deposited on various surfaces relevant to catalysis, magnetism, photophysics, medicine as well as for fabrication of sensors and other molecular devices. This project was particularly focused on the development of novel synthesis strategies for the (post-) functionalization of magnetic POTs with organoarsonates (RAsVO3^2–) and organophosphonates (RPVO3^2–) groups with the eventual aim to allow precise electrical contacts to such molecules, e. g. in two-junction scanning tunneling microscopy experiments in interest of molecular spintronics. The implementation of the project allowed significant deepening our knowledge about the synthetic pathways for functionalization of POTs with organoarsonates having terminal aminogroups. At that we have established that despite obvious structural analogies between RAsO3^2− and RPO3^2− groups there are often substantial differences in their reactivity towards POTs meaning their ability to bind to specific places in the POT skeleton and act as co-ligands for stabilization of multinuclear cores of magnetic heterometals. Moreover, even structurally closed organoarsonatesand organophosphonates-functionalized POTs exhibit quite different stability and hence also quite different reactivity in aqueous and organic media. We have also shown, that functionalization with organoarsonates allows to isolate novel structural types of polyoxometalates, unknown before, either by direct stabilization of unusual POT skeletons with organic groups or by the use of organo-functionalized polyanions as novel precursors for the POT complexes with transition and rare earth metal ions. Such, we were able to stabilize an uncommon coordination number of 6 with triagonal prismatic coordination geometry for a wide range of LnIII ions and YIII in P4W27 POT-cages. In addition, we have demonstrated that phenylphosphonate-functionalized POTs of Wells-Dawson-structural type, P2W17(PhP)2, show unusual reactivity in reaction with lanthanides and YIII resulted in the loss of one WVI centre – in other words, formation of an additional lacunary or vacant site in the POT framework, without a rearrangement of the complete POT-skeleton and even without a loss of organic functions. Several complexes of POT with LnIII ions and multinuclear {FeIII3} and {FeIII10} cores which have several organic anchor-groups located on the same side and the same height level towards polyanions have been isolated. These species thus represent especially attractive candidates for the further deposition on metal surfaces (e. g. Au0, Pd0, Pt0 and Cu0) and for consequent C-AFM studies and fabrication of the two-terminal devices as well as for development of heterogeneous catalytic systems for various catalytic transformations. This study also further highlights very reach perspectives of novel discoveries in POT chemistry in terms of structures and electronic, electrochemical and magnetic properties which could be achieved via the bi-functionalization approach.
Projektbezogene Publikationen (Auswahl)
-
Polyoxometalates with separate lacuna sites. Chemical Communications, 56(94), 14857-14860.
Wang, Wenyan; Izarova, Natalya V.; van Leusen, Jan & Kögerler, Paul
-
Polyoxotungstate Archetype {P4W27} and its 3d Derivatives. Chemistry – A European Journal, 27(33), 8500-8508.
Iftikhar, Tuba; Izarova, Natalya V.; van Leusen, Jan & Kögerler, Paul
-
Trigonal Prismatic Coordination of Discrete Rare Earth Ions, Enforced by the Polyoxotungstate [P4W27O99(H2O)]16–. Chemistry – A European Journal, 27(53), 13376-13383.
Iftikhar, Tuba; Izarova, Natalya V.; van Leusen, Jan & Kögerler, Paul
-
Bifunctionalized Polyoxotungstates: Dilacunary Keggin Clusters Incorporating FeIIIand Organoarsonate Constituents. Crystal Growth & Design, 23(1), 434-441.
Faassen, Fabian; Izarova, Natalya V.; van Leusen, Jan & Kögerler, Paul
-
Organoarsonates Enable Single-Site Condensation of Hexalacunary {P2W12} Polyoxotungstates. Inorganic Chemistry, 63(1), 99-107.
Iftikhar, Tuba; Izarova, Natalya V. & Kögerler, Paul
-
Tris-decorated multi-iron polyoxotungstates. Dalton Transactions, 52(3), 546-550.
Izarova, Natalya V.; Faassen, Fabian & Kögerler, Paul
