Phthalocyaninato Transition Metal / Lanthanide-Supported Polyoxometalate Complexes for the Study of Large-Area Molecular Charge Transport Properties
Final Report Abstract
A series of organic-inorganic hybrid compounds consisting of one or two LnPc moieties grafted directly onto the fully oxidized {V12}-nuclearity polyoxovanadate cage were synthesized and fully characterized. The paramagnetic compounds (nBu4N)3[HV12O32Cl(LnPc)] and (nBu4N)2[HV12O32Cl(LnPc)2], where Ln = SmIII −ErIII , LuIII including YIII , feature a non-photoinduced intra- and intermolecular charge transfer in the condensed state resulting in a partial reduction of V(3d) centres from VV to VIV. The charge transfer between the LnPc-functionalized polyoxovanadate ground-state structures is mediated by their countercations. These findings were confirmed by experimental (electron paramagnetic resonance, DC and AC SQUID, laser photolysis transient absorption spectroscopy, and electrochemistry) and computational (DFT, molecular dynamics, and model Hamiltonian approach) methods. It was demonstrated that (nBu4N)3[HV12O32Cl(DyPc)] is a field-induced single molecule magnet with a maximum relaxation time in the order of 10^−3 s. The synthesized hybrid compounds proved to form robust and stable self-assembled monolayers (SAMs) on atomically-flat template-stripped gold substrates (AuTS) showing good electrical conductance by using an eutectic Ga–In tip. The DFT calculations led to a conclusion that the occupied and unoccupied frontier orbitals in the hybrids are delocalized on the phthalocyanine ligand and polyoxovanadate, respectively, thus responsible for creating tunnelling transmission channels. The tendency of the phthalocyanine group to form intermolecular π−π interactions was further exploited in the formation of stable monolayers of magnetic PcDy-{V12} and (PcDy)2-{V12} adopting the face-on orientation on highly oriented pyrolytic graphite (HOPG). It was possible for the first time to show the room-temperature multistate switching behavior of polyoxovanadates within an extended 2D molecular layer, rather than just of an isolated immobilized molecule. Reproducible local removal of hybrid molecules by the scanning tunnelling microscopy tip at the nanoscale forming nanostructures (30 to 150 nm2) was successfully performed. The obtained results lay the foundation for further studies of these highly promising donor−acceptor hybrid compounds with the far-reaching goal of their future implementation in molecularly powered classic and quantum sensor / computing technologies.
Publications
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Hybrid Molecular Magnets with Lanthanide- and Countercation-Mediated Interfacial Electron Transfer between Phthalocyanine and Polyoxovanadate. Inorganic Chemistry, 62(9), 3761-3775.
Werner, Irina; Griebel, Jan; Masip-Sánchez, Albert; López, Xavier; Załęski, Karol; Kozłowski, Piotr; Kahnt, Axel; Boerner, Martin; Warneke, Ziyan; Warneke, Jonas & Monakhov, Kirill Yu.
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Influence of Polyoxovanadate and Phthalocyanine on 4f Electron Transfer in Gold-Confined Monolayers Probed with EGaIn Top Contacts. ACS Applied Nano Materials, 6(24), 22643-22650.
Soni, Saurabh; Werner, Irina; Aidi, Michael; Moors, Marco; Mthembu, C. Lungani; Zharnikov, Michael; Havenith, Remco W. A.; Monakhov, Kirill Yu. & Chiechi, Ryan C.
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Multistate switching of scanning tunnelling microscopy machined polyoxovanadate–dysprosium–phthalocyanine nanopatterns on graphite. Nanoscale Horizons, 9(2), 233-237.
Moors, Marco; Werner, Irina; Bauer, Jens; Lorenz, Jonas & Monakhov, Kirill Yu.
