Research

 

 

Our work motivation

The use of individual vanadium-oxo and copper-oxo clusters and (d,f-)metal-organic complexes with structurally exposed anchoring groups in technologically relevant charge/spin transport and optical mechanisms on substrate surfaces as well as in supported-metal complex heterogeneous catalysis.

High risk

We go beyond digital information processing toward multi-level state processing, paving the way for neuromorphic computing.

High gain

We aim to construct molecular platforms that may integrate the storage and processing of data in the same device.

Disciplines

Our work spans chemistry and physics sub-disciplines, including Inorganic and Organic Chemistry, Electrochemistry, Spectroscopy, Magnetochemistry, Quantum Chemistry, Surface Physics, Condensed Matter Physics, Optics, and Photophysics.

Main research fields

Coordination and supramolecular chemistry, molecular electronics and spintronics, computational chemistry, and surface science.

  


 

“The combined understanding of matter at the atomic and molecular levels using simultaneous experimental and computational means is at the heart of our highly explorative, interdisciplinary, and collaborative research and of special value to the chemistry and physics communities, experimentalists and theoreticians, working in the mainstream areas of modern coordination chemistry and single-molecule electronic and spintronic devices for applications in the next generation information technology.”

 


 

 

TOPIC 1: Synthesis, structure, spectroscopy, and magnetism of host-guest and organically modified polyoxovanadates

 

 

Polyoxovanadates (POVs) are vanadium-oxo clusters which are divided into four general families: ''fully oxidized'' (VV), mixed-valence (VV/VIV and VIV/VIII), ''fully-reduced'' (VIV), and "highly-reduced" (VIII) species

The complexity of the POV’s electronic and magnetic structures is unique and the underlying theory needs a systematic and comprehensive investigation by involving quantum mechanical calculations along with the direct measurements of these (polyanionic) molecules by solution and solid-state NMR, EPR and UV-Vis spectroscopic methods, cyclic voltammetry, and SQUID magnetometry. 

Many questions concerning their inorganic synthesis, reactivity in aqueous and pure organic solutions, molecular magnetism, spectroscopy, excited states, and computational application remain entirely open. The thorough exploration of their chemical and physical properties enables us to study fundamental surface physics phenomena at the single-molecule level and at the level of thin films using scanning tunneling microscopy and other surface characterization techniques. 

These magnetic molecules have great potential as components of technological applications including redox-flow batteries, photovoltaic cells, light-emitting diodes, nanophotonics, and quantum computing.

 

POSTDOC: Dr. Maria Stuckart

STUDENTS: Oliver Linnenberg, M.Sc.; Ricarda Pütt, M.Sc.; Maria Glöß, M.Sc.

 

 

           

 

References

[1] O. Linnenberg, M. Moors, A. Solé-Daura, X. López, C. Bäumer, E. Kentzinger, W. Pyckhout-Hintzen, K. Yu. Monakhov, "Molecular characteristics of a mixed-valence polyoxovanadate {VIV/V18O42} in solution and at the liquid-surface interface", J. Phys. Chem. C 2017, 121, 10419–10429.

[2] O. Linnenberg, P. Kozłowski, C. Besson, J. van Leusen, U. Englert, K. Yu. Monakhov, "A V16-Type Polyoxovanadate Structure with Intricate Electronic Distribution: Insights from Magnetochemistry", Cryst. Growth Des. 2017, 17, 2342–2350.

[3] K. Yu. Monakhov, W. Bensch, P. Kögerler, "Semimetal-Functionalized Polyoxovanadates", Chem. Soc. Rev. 201544, 8443–8483.

[4] K. Yu. Monakhov, O. Linnenberg, P. Kozłowski, J. van Leusen, C. Besson, T. Secker, A. Ellern, X. López, J. M. Poblet, P. Kögerler, "Supramolecular Recognition Influences Magnetism in [X@HVIV8VV14O54]6− Self-Assemblies with Symmetry-Breaking Guest Anions", Chem. Eur. J. 201521, 2387–2397.

See also:

[5] E. Antonova, C. Näther, P. Kögerler, W. Bensch, "Organic Functionalization of Polyoxovanadates: Sb-N Bonds and Charge Control", Angew. Chem. Int. Ed. 2011, 50, 764–767.

[6] A. Müller, R. Sessoli, E. Krickemeyer, H. Bögge, J. Meyer, D. Gatteschi, L. Pardi, J. Westphal, K. Hovemeier, R. Rohlfing, J. Döring, F. Hellweg, C. Beugholt, M. Schmidtmann, "Polyoxovanadates: High-Nuclearity Spin Clusters with Interesting Host−Guest Systems and Different Electron Populations. Synthesis, Spin Organization, Magnetochemistry, and Spectroscopic Studies", Inorg. Chem. 199736, 5239–5250.

[7] A. Müller, H. Reuter, S. Dillinger, "Supramolecular Inorganic Chemistry: Small Guests in Small and Large Hosts", Angew. Chem. Int. Ed. Engl. 199534, 2328–2361.

 

 

TOPIC 2: Computational chemistry of polyoxometalates

 

 

Polyoxometalates (POMs) are metal-oxo clusters containing early transition metals (V, Nb, Ta, Mo, and W) in their high oxidation states. POMs show a large structural versatility and have actual and potential applications in catalysis, biochemistry, nanoscale magnetism, nanoelectronics, and the design of nanostructured composite materials.

Because these compounds are usually formed via complex condensation processes and exhibit diverse structural motifs, a rational synthesis of POMs with the programmed properties is often a very cumbersome process. To assist further development and to boost the progress in the synthetic chemistry of POMs, we explore their structural principles and the POM's structure-property relations using quantum mechanical calculations at the density functional theory (DFT) level. In addition, we investigate how the geometric, electronic, and spectroscopic properties of POMs are affected by their interactions with immediate environment.

Recently, we reported results of a theoretical study of heteropolyoxovanadates of the type V14E8, which have been a focus of attention of many experimental POM groups since early 1990’s. Our study provided a detailed DFT description of the synthesized α- and β-V14E8 isomers and, furthermore, revealed that a brand new γ-V14E8 isomer exhibiting an intermediate stability can be potentially isolated in near future.

We also perform DFT studies of POMs on substrate surfaces and calculate their scanning tunneling microscopy (STM) images.

 

  

alpha-{V14E8O50}

gamma-{V14E8O50}

beta-{V14E8O50}

     

         

References

[1] A. Kondinski, T. Heine, K. Yu. Monakhov, "Rotational Isomerism, Electronic Structures, and Basicity Properties of “Fully-Reduced” V14-Type Heteropolyoxovanadates", Inorg. Chem. 201655, 3777–3788.

 

  

TOPIC 3: Synthesis, structure, and magnetism of coordination clusters with structurally exposed anchoring groups

 

 

We focus on the synthesis and optimization of multidentate redox-active organic ligands and their d- and f-metal coordination compounds with surface anchoring groups such as, for example, thiols (–SH), methyl sulfides (–SMe), 1,2-dithiolanes (–S-S–), aliphatic heterocyclic thioethers (–S–), etc. 

Sulfur-based anchoring groups can be used as functional components of Schiff base ligands, carboxylic acids, amino alcohols, and other organic systems to modulate the molecule–surface interactions.

The systematic investigation of the adsorption phenomena of magnetic metal-organic molecules (for example, single-molecule magnets) on various metallic surfaces and thus of the generated moleculesubstrate interfaces is appealing and worthwhile because it allows us to create necessary guidelines for the fine-tuning of the structure and composition of our molecular material and, in particular, the metal-ligand coordination bonds

We aim to improve the structural, thermal, and redox stability of these molecular magnets in order to achieve their intact deposition from solution or from the solid phase onto metallic electrodes and, eventually, to preserve the key magnetic characteristics of anchored individual molecules. The main goal is to engineer electrically accessible metal complexes (molecular spin qubits, spin transistors, etc.) for the future compact and energy-efficient nanodevices.

 

STUDENTS: Sebastian Schmitz, M.Sc. (Kögerler group).

 

 

{Ni4}

{Mn11Tb4}

 

  

{Ni6} and {Ni8}

{Cr6Ln14}, Ln = Dy or Tb

 

 

References

[1] S. Schmitz, J. van Leusen, N. V. Izarova, Y. Lan, W. Wernsdorfer, P. Kögerler, K. Yu. Monakhov, "Supramolecular 3d-4f single-molecule magnet architectures", Dalton Trans. 2016, 45, 16148–16152.

[2] S. Schmitz, J. van Leusen, A. Ellern, P. Kögerler, K. Yu. Monakhov, "Thioether-Terminated Nickel(II) Coordination Clusters with {Ni6} Horseshoe- and {Ni8} Rollercoaster-Shaped Cores", Inorg. Chem. Front. 2016, 3, 523–531.

[3] S. Schmitz, J. van Leusen, A. Ellern, P. Kögerler, K. Yu. Monakhov, "A Thioether-Decorated {Mn11Tb4} Coordination Cluster with Slow Magnetic Relaxation", Inorg. Chem. Front. 20152, 1095–1100.

[4] V. Heβ, F. Matthes, D. E. Bürgler, K. Yu. Monakhov, C. Besson, P. Kögerler, A. Ghisolfi, P. Braunstein, C. M. Schneider, "Adsorption Phenomena of Cubane-Type Tetranuclear Ni(II) Complexes with Neutral, Thioether-Functionalized Ligands on Au(111)", Surf. Sci. 2015641, 210–215.

[5] A. Ghisolfi, K. Yu. Monakhov, R. Pattacini, P. Braunstein, X. López, C. de Graaf, M. Speldrich, J. van Leusen, H. Schilder, P. Kögerler, "A Comparative Synthetic, Magnetic and Theoretical Study of Functional M4Cl4 Cubane-Type Co(II) and Ni(II) Complexes", Dalton Trans. 201443, 7847–7859.

See also:

[6] A. Cornia, M. Mannini, P. Sainctavit, R. Sessoli, "Chemical Strategies and Characterization Tools for the Organization of Single Molecule Magnets on Surfaces", Chem. Soc. Rev. 201140, 3076–3091.

[7] J. J. Parks, A. R. Champagne, T. A. Costi, W. W. Shum, A. N. Pasupathy, E. Neuscamman, S. Flores-Torres, P. S. Cornaglia, A. A. Aligia, C. A. Balseiro, G. K.-L. Chan, H. D. Abruña, D. C. Ralph, "Mechanical Control of Spin States in Spin-1 Molecules and the Underscreened Kondo Effect", Science 2010, 328, 1370–1373.