Robert Ranecki

@article{Ranecki2024,

title = {Self-Assembly of the Chiral Donor–Acceptor Molecule DCzDCN on Cu(100)},

author = {Robert Ranecki and Benedikt Baumann and Stefan Lach and Christiane Ziegler},

url = {https://pubs.acs.org/doi/10.1021/acsami.3c16918},

doi = {10.1021/acsami.3c16918},

issn = {1944‑8252},

year  = {2024},

date = {2024-02-11},

urldate = {2024-02-11},

journal = {ACS Applied Materials & Interfaces},

volume = {16},

issue = {7},

pages = {9108–9116},

abstract = {Donor–acceptor (D–A) structured molecules are essential components of organic electronics. The respective molecular structures of these molecules and their synthesis are primarily determined by the intended area of application. Typically, D–A molecules promote charge separation and transport in organic photovoltaics or organic field-effect transistors. D–A molecules showing a larger twist angle between D and A units are, e.g., essential for the development of high internal quantum efficiency in organic light-emitting diodes. A prototypical molecule of this D–A type is DCzDCN (5-(4,6-diphenyl-1,3,5-triazine-2-yl)benzene-1,3-dinitrile). In most cases, these molecules are only investigated regarding their electronic and structural interaction in bulk aggregates but not in ultrathin films supported by a metallic substrate. Here, we present growth and electronic structure studies of DCzDCN on a Cu(100) surface. We used a complementary approach through the use of scanning tunneling microscopy/spectroscopy (STM and STS), ultraviolet/inverse photoemission spectroscopy (UPS and IPES), and single-molecule density functional theory (DFT) calculations. This method combination enabled us to investigate the adsorption geometry (STM) and the local electronic states near the Fermi energy (EF) of a single adsorbed molecule (using STS) and to compare these data with the integral overall electronic structure of the DCzDCN/Cu(100) interface (using UPS/IPES). The orientation of the molecules with the donor part toward the substrate results in a chiral resolution at the interface due to the molecular as well as the substrate symmetry and additional strong molecular electrostatic forces induced by the charge distribution of the twisted dicarbonitrile part. Thus, the formation of various bulk-unlike homochiral structures and the appearance of hybrid interface states modify the molecular electronic properties of the DCzDCN/Cu(100) system, e.g., the transport gap by −1.3 eV compared to that of a single DCzDCN molecule. This may be useful not only for optoelectronic applications but also in organic spintronics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ranecki2023,

title = {Spin-Flip Inelastic Electron Tunneling Spectroscopy on a CuCu4 Metallacrown Complex on Au(111)},

author = {Robert Ranecki and Stefan Lach and Anne Lüpke and Eva Rentschler and Christiane Ziegler},

url = {https://pubs.acs.org/doi/10.1021/acs.jpcc.3c01291},

doi = {10.1021/acs.jpcc.3c01291},

year  = {2023},

date = {2023-06-29},

urldate = {2023-06-29},

journal = {The Journal of Physical Chemistry C},

volume = {127},

issue = {27},

pages = {13186–13195},

abstract = {Spin-flip inelastic tunneling spectroscopy (SF-IETS) is an outstanding technique to investigate elementary spin excitation of adsorbed atoms, molecules, and their assemblies on surfaces. The analysis of the measured spectra provides access to the spin interactions within adsorbed spin systems and their coupling with the substrate electrons. Here, we use SF-IETS in combination with different perturbative electron transport model simulations to explore the spin excitation processes in the Cu(II)[12-MCCu(II)N(Shi)-4] metallacrown molecule (CuCu4), containing five half-spin centers, after adsorption on an Au(111) surface. In contrast to published SF-IETS spectra of other multispin-carrying systems decoupled from the metal surface, showing a step-like function, the signatures of the CuCu4/Au(111) systems differ significantly. These spin-flip signatures could be reproduced by considering spin–spin exchange scattering with the substrate electron bath using an up to 3rd-order perturbative electron transport model in the simulations. The results give access to the system’s superexchange coupling constants with the resulting spin ground state and lead to a better understanding of the spin dynamics of such multiple spin-bearing molecules. Our results do not only give insight into a system that may be utilized in molecular spintronics but may open a route to manipulate spins in nonmagnetic metals on a nanometer scale.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ranecki2022,

title = {Competing Intramolecular Superexchange Interactions in the CuFe4 Metallacrown on Au(111)─An Inelastic Tunneling Spectroscopy Study},

author = {Robert Ranecki and Stefan Lach and Anne Lüpke and Angeliki Athanasopoulou and Eva Rentschler and Christiane Ziegler},

url = {https://pubs.acs.org/doi/10.1021/acs.jpcc.2c02551},

doi = {10.1021/acs.jpcc.2c02551},

year  = {2022},

date = {2022-09-09},

urldate = {2022-09-09},

journal = {The Journal of Physical Chemistry C},

volume = {126},

issue = {37},

pages = {15907–15914},

abstract = {Spin-flip inelastic tunneling spectroscopy (SF-IETS) at low temperatures allows the electrical characterization of surface magnetism, particularly for molecule/substrate systems which can be interesting for molecular spintronics. Here, SF-IETS was used to explore the competing character of intramolecular superexchange interactions on a device-compatible metallic substrate. For this purpose, the multinuclear metallacrown system CuFe4, [Cu(ii)(DMF)2Cl2[12-MCFe(III)N(Shi)-4](DMF)4·2DMF], on Au(111) and its resulting “surface” spin ground state were studied. After the deposition of CuFe4 molecules by a solution-based technique onto a Au(111) surface, the CuFe4 system exhibits an evident hallmark of inelastic tunneling, that is, step-like features on the differential conductance spectra, which we attribute to spin-flip excitations. By analyzing the experimental curve with a second-order electron transport model simulation, we determined the exchange coupling constants and the spin ground state. Our results are compared with those spin ground states published in the literature for this compound based on the broken-symmetry density functional theory calculations and temperature-dependent magnetic susceptibility measurements.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}